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Residual feed intake (RFI) is an important trait of feed efficiency that has been increasingly considered in the breeding objectives for dairy cattle. The objectives of this study were to estimate the genetic parameters of RFI and its component traits, namely, dry-matter intake (DMI), body weight (BW), and energy-corrected milk (ECM), in lactating Holstein cows; we thus developed a system for genomic evaluation of RFI in lactating Holstein cows and explored the associations of the RFI of heifers and cows. The RFI values were calculated from 2,538 first (n = 2,118) and second (n = 420) lactation Holsteins cows between 2020 and 2024 as part of the STgenetics EcoFeed® program. Of the animals, 1,516 were heifers from the same research station with previously established RFI values. After quality control, 61,283 single-nucleotide polymorphisms were used for the analyses. Univariate analyses were performed to estimate the heritabilities of RFI and its components in lactating cows; bivariate analyses were then performed to estimate the genetic correlations between the RFI of heifers and lactating cows using the genomic best unbiased linear prediction method. Animals with phenotypes and genotypes were used as the training population, and animals with only genotypes were considered the prediction population. The reliability of breeding values was obtained by approximation based on partitioning a function of the accuracy of the training population's genomic estimated breeding values (GEBVs) and magnitudes of genomic relationships between the individuals in the training and prediction populations. The heritability estimates (mean ± SE) of the RFI, DMI, ECM, and BW were 0.43 ± 0.07, 0.44 ± 0.04, 0.40 ± 0.05, and 0.46 ± 0.04, respectively. The average reliability of the GEBVs for RFI from the training and prediction populations were 44% and 30%, respectively. The genetic correlations for the RFI were 0.42 ± 0.08 between heifers and first lactation cows and 0.34 ± 0.06 between heifers and first and second lactation cows. Our results show that the genetic components of RFI are not fully carried over from heifers to cows and that there is re-ranking of the individuals at different life stages. Selection of animals for feed efficiency on a lifetime basis thus requires accounting for the efficiencies during animal growth and milk production as a lactating cow. [ABSTRACT FROM AUTHOR]

In this study, the effects of fully littered, slatted and their varying combinations on growth, performance, carcass and meat quality characteristics in broiler chickens were investigated. In the experiment, five treatment groups were formed as fully littered (FL), fully slatted (FS), 1/3 littered + 2/3 slatted (2/3 SF), 1/2 littered + 1/2 slatted (1/2SF), 2/3 littered + 1/3 slatted (1/3 SF). Each treatment group included 5 replicates (24 chicks in each) and a total of 600 male-female mixed fast growing broiler chicks (Ross-308) were used during 6 weeks. Weekly body weight (BW, g), feed intake (FI, g), feed conversion ratio (FCR, g.feed intake/g.weight gain), livability (%) and EPEF (European Production Efficiency Factor) were determined as performance characteristics. Carcass yield (CY, %), and the percentages of abdominal fat (AFP, %), edible internal organs (EIOP, %), gizzard (GP, %), breast (BRP, %) and thigh (TP, %) meat were the carcass characteristics. Meat quality measured by pH and color (L*: lightness, a*: redness, b*: yellowness) of breast and thigh meat, and occurrence of white striping and hemorrhaging in breast meat. The weekly BW differences among the floor treatments were significant (P < 0.01), and 1/3SF broilers were the heaviest at slaughter age (3311.6 g). The 6-week FCR in FS broilers was significantly worse than the others (1.471), but FI, livability and EPEF were similar among treatments. AFP tended to be higher in FL birds (P = 0.066), while CY, EIOP, GP, BRP and TP did not differ between groups. Breast pH was similar between treatments, with 1/2SF showing the highest (6.34) and FL the lowest (6.24) breast pH (P < 0.01). The partially slatted systems caused lighter, redder and yellower color values in breast meat (P < 0.01) than the fully littered or slatted systems, but did not change the color of the thigh meat. White striping and hemorrhaging in breast meat were not affected by the floor treatments. This study suggests that the use of partially slatted systems in broiler chickens improves meat color without compromising performance traits (body weight, feed efficiency, EPEF), litter moisture and slaughter traits and these systems could be an alternative to fully littered systems. [ABSTRACT FROM AUTHOR]

The residual intake and gain (RIG) aims to select animals that present low feed intake in relation to the expected. This study aimed to evaluate the associations of selection for RIG with performance and carcass traits in Nellore cattle. Initially, residual feed intake (RFI) and residual gain (RG) were determined. From this, the RIG was calculated, and the animals were classified as efficient and inefficient for RIG. The efficient animals for RIG showed higher daily weight gain (DWG), Longissimus muscle area (LMA), and mid-test metabolic body weight (MMBW) than the inefficient ones. No significant correlations were found between subcutaneous fat thickness (SFT), marbling (MAR), LMA, MMBW, and the RIG. Thus, it’s concluded that the RIG is a measure that can be used to identify and select animals with higher rates of DWG and LMA without changes in the dry matter intake (DMI), SFT, and MAR. However, this index should still be observed with caution, as it may be dependent on body size. Based on the findings, the selection of animals according to the RIG can be an important factor to generate phenotypic evolution in characteristics such as weight gain and rib eye area without adverse effects on the carcass fat deposition. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of varying stocking densities during the first 10 days on the performance, welfare, slaughter and meat quality characteristics of broiler chickens in the subsequent period (11–42 days). In the study, treatments representing 3 different stocking densities with the same group sizes were established and a total of 432 d-old chicks were used. In the first 10 days of the rearing period, treatments of 18 (SD18), 27 (SD27) and 36 (SD36) chicks per m2 were formed, and at 11 days of age, chicks in all treatments were reared at a density of 18 chicks/m2. Body weight differences in SD18, SD27 and SD36 treatments at 10 and 42 days of age were significant (P < 0.05), they were 252.6, 254.3 and 241.5 g in SD18, SD27 and SD36 groups at 10 days and 2961.1, 2874.8 and 2842.7 g at 42 days of age, respectively. In the first 10 days of growing period, SD36 showed a significant difference (P < 0.05) from the other groups in feed intake and feed conversion ratio, but this was not significant at slaughter age. The livability at 10 and 42 days was not different among treatments and was between 98.6 and 99.3% and 93.5–93.8%, respectively. The uniformity at 10 days was significant among the stocking density groups (P < 0.05) and the best uniformity level was obtained in the SD36 group, the differences in CV values at 42 days were not significant among the treatments. EPEF (European production efficiency factor) values were not different between the groups, the highest numerical value was determined in the SD36 group. Foot pad dermatitis, hock burn and breast burn levels were significantly higher in SD18 chickens (P < 0.05), however incidence of finger crookedness and valgus-varus deformity did not differ between the treatments. The litter moisture contents were similar between treatments, and ranged from 25.6 to 32.6%. Different stocking density treatments during the first 10 days of the experiment had no significant effect on slaughter, abdominal fat, carcass parts, color and pH values in the breast and thigh meat. In conclusion, rearing broiler chickens by dividing the poultry house area by half during the first 10 days (36 birds/m2) could help to improve the overall productivity (EPEF) by providing ease of maintenance, efficient heating and better control. [ABSTRACT FROM AUTHOR]

The trail aimed to explore the effect of dietary supplementation of curcumin loaded olive oil nanoemulsion (CUR‐OLNE) on growth performance, feed utilization, blood biochemical, redox status, and immune response of Litopenaeus vannamei shrimp, considering the economic efficiency of supplementation. A total of 280 healthy shrimps (3.42 ± 0.02 g) were randomly distributed into five equal groups and were fed diets containing 0 (CUR‐OLNE0), 5(CUR‐OLNE5), 10(CUR‐OLNE10), 15(CUR‐OLNE15) and 20 (CUR‐OLNE20) mg CUR‐OLNE/kg diet, respectively for 16 weeks. Among CUR‐OLNE treated groups, CUR‐OLNE20 showed the highest growth performance and feed utilization traits, including final body weight, specific growth rate, feed conversion ratio, and protein efficiency ratio. Notably, the photomicrographs provided further compelling evidence regarding the potential effect of CUR‐OLNE supplementation on muscle structure and integrity. Compared to the control, the levels of blood protein significantly induced in CUR‐OLNE15 and CUR‐OLNE20 treated groups (p < 0.05). All CUR‐OLNE ‐supplemented groups possessed lower activities of liver enzymes as well as the levels of urea and creatinine compared to the control (p < 0.05). The addition of 20 mg CUR‐OLNE/kg diet decreased the concentrations of cortisol, glucose and triglycerides. The dietary treatment significantly improved the secretion of digestive enzymes, including amylase, lipase, and protease. The lowest levels of Malondialdehyde and the highest levels of total antioxidant capacity, super oxide dismutase, catalase, lysozyme and immunoglobulin M were detected in both of CUR‐OLNE15, and CUR‐OLNE20 treated groups compared to the control (p < 0.05). There were considerable significant effects of dietary supplementation of CUR‐OLNE on economic efficiency. In conclusion, the application of nanocarriers for the delivery of dietary immune stimulants such as CUR‐OLNE to Litopenaeus vannamei shrimp is a promising strategy for improving shrimp nutrition. The addition of 20 mg CUR‐OLNE/kg to the diets of can be recommended as an affective intervention to improve growth performance, feed utilization, and health status of shrimp. Implementing this intervention can maximize the economic efficiency of shrimp farming while promoting sustainable practices in the industry. [ABSTRACT FROM AUTHOR]

Chromium (Cr) is a mineral that helps animals subjected to stressful conditions. The suckling period is characterized by several stressful episodes, particularly during the first hours after birth and at weaning. There is little consumption of concentrate by calves in the first weeks of life; consequently, consuming any supplement added to feed would be negligible. Thus, the hypothesis was that the calves would take it in earlier if Cr were consumed in a milk replacer instead. Therefore, our study aimed to determine whether including organic Cr in calf feed (via milk replacer or concentrate) during the suckling phase would improve calf health and growth performance. Twenty-four male Holstein calves with an average age of 8 ± 4 days and 39.8 ± 6.9 kg average body weight were used. Calves were randomly divided into three groups: (a) Chromium-Milk (CR-M), receiving 4 mg Cr/animal/day via milk replacer during the 60 experimental days of suckling (n = 8); (b) Chromium-Concentrate (CR-C), receiving 4 mg Cr/animal/day via concentrate (n = 8); (c) Control (C), animals that did not receive Chromium (n = 8). The experiment lasted 75 days, divided into two well-defined stages: suckling (1–60 days) and weaning (61–75 days). Body weight weekly, daily feed intake, and blood samples taken every two weeks during the experiment were evaluated. At the end of the experiment, the apparent digestibility evaluation was carried out, with the results of weight and consumption carried out, and a feed efficiency analysis was carried out. It was observed that the inclusion of organic Cr (regardless of whether it was milk or concentrate) increased body weight gain (kg) for the CR-C group: 41.8 kg, CR-M: 40.4 kg compared to the C: 34.2 kg (p = 0.01). The protein digestibility was higher in the CR-M group (52%, p = 0.05). Cr consumption increased Cr concentrations in the serum of the calves and was higher in the first week in the animals in the CR-M group. This did not happen for the C group; however, with higher concentrate consumption, Cr concentrations increased and remained high until the end of the experiment. Glucose concentrations were higher in the groups that consumed Cr. Total protein concentrations were higher in the CR-M and CR-C groups than in group C. Immunoglobulin A concentrations were higher in groups CR-C and CR-M than in group C (days 40 and 60). In conclusion, the adding Cr to calf feed improves their health, indirectly favors growth performance, and increases protein digestibility. [ABSTRACT FROM AUTHOR]

The re-integration of former foodstuffs, such as bakery products (BP), into pig feed reduces the feed-food competition and increases the sustainability of pig production. Nevertheless, there are concerns about the altered fatty acid profile in BP compared to standard diets and their effects on meat quality and the intestinal microbiome. The present study investigated the effects of replacing 30% cereal grains with BP in the diet on performance, microbiome composition and metabolites in feces of fattening pigs, economic aspects and meat quality characteristics. A total of 132 pigs (Large White × Piétrain; 11 weeks of age) were fed two diets containing 0 or 30% BP until reaching slaughter weight in three replicate batches. Fecal samples were collected for 16S rRNA amplicon sequencing after 6 weeks, whereas body fat samples were collected after 9 weeks on the diet. The results showed that BP can replace cereals in pig diets by up to 30% without impairing animal performance, while improving feed efficiency and reducing feed costs by 9% compared to the control. Additionally, pigs fed the BP diet had a 50%-higher n-3 fatty acid content in the neck and abdominal fat compared to the control. The improved feed efficiency in BP-fed pigs may be related to positive effects on the fecal microbiome, such as a higher alpha diversity and a reduction of fungi and yeasts. Our study provides valuable insights into the benefits of including BP in diets of fattening pigs, which should be investigated in future studies on other BP types. [ABSTRACT FROM AUTHOR]

This study compared the effects of feeding a new strain of Saccharomyces cerevisiae HSA2020 with a commercial strain on in vitro rumen fermentation and production performance of dairy cows. Permeate was used as a substrate for the laboratory production of the new strain of S. cerevisiae after the hydrolysis by β-galactosidase (5000 µ/mL at 37°C). Two experiments were conducted: in Experiment 1, the effects of three levels (1, 2 and 3 g/kg dry matter) of S. cerevisiae on in vitro ruminal fermentation kinetics were evaluated. In Experiment 2, for 60 days, sixty multiparous Holstein cows (639±24.8 kg BW, 3±1 parity, 7±1 days in milk, with a previous milk production of 23±2.0 kg/d) during the previous lactation, were randomly assigned to 3 treatments in a completely randomized design. Cows were fed without any additives (control treatment) or supplemented with 2 g/kg feed daily of laboratory produced (PY) or commercial (CY) S. cerevisiae. In Experiment 1, inclusion of PY and CY increased (P<0.05) gas production, propionate, and nutrient disappearance, while decreased (P<0.05) methane production and protozoal count. Moreover, in Experiment 2, PY followed by CY increased (P<0.01) nutrient digestibility, and serum concentrations of total protein, albumin, and glucose (P<0.05). Higher daily milk yield, and milk energy output were observed with PY and CY without affecting concentrations of milk components or milk fatty acid profile. Compared to control, increased feed efficiency was observed with PY and CY. Compared to PY, CY increased serum concentrations of urea-N and decreased triglycerides, while PY decreased serum aspartate transaminase and increased concentration of conjugated linoleic acids in milk. In early lactating cow diets, both strains of S. cerevisiae improved production performance at 2 g/kg, and minimal differences between strains were found. [ABSTRACT FROM AUTHOR]

Context: Animal feed production systems have been suffering from a shortage of feedstuffs because of competition for these resources with human food consumption. The use of by-products can increase efficiency and circularity in production chains, reducing this competition. Aims: This study investigated the impacts of Paullinia cupana peel meal (PCPM) on the growth performance, meat quality, and haematological and serum biochemical parameters of slow-growing broilers. Methods: Two hundred and forty slow-growing male Label Rouge broilers were distributed in a completely randomised experimental design. The treatments consisted of five inclusion levels of PCPM (0%, 2.5%, 5.0%, 7.5%, and 10%) in the diets, with four replicates of 12 birds each. Growth performance data, and haematological and serum biochemical parameters were monitored. Twelve broilers per treatment were slaughtered for meat-quality analysis. Key results: In the starter stage, there was a significant increase (P < 0.05) in feed intake and weight gain with and increasing inclusion level of PCPM in the diet. However, this effect diminished in the final stage. Even with a reduction (P < 0.05) in feed intake during the final stage, the broilers showed an increase (P < 0.05) in weight gain and improvement (P < 0.05) in feed efficiency in the cumulative performance. Broilers fed diet with a higher inclusion level of PCPM had lower (P < 0.05) concentrations of erythrocytes and blood triglycerides, as well as a decreased haematocrit percentage. However, these broilers exhibited higher (P < 0.05) results for mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. Broilers fed diets with a higher inclusion level of PCPM were heavier (P < 0.05) at slaughter, with higher (P < 0.05) carcass yield, greater (P < 0.05) liver, gizzard, and heart weight, increased breast, drumstick, and thigh yields, and higher moisture and lipid contents in the breast. Conclusions: The high inclusion levels of PCPM in diets for slow-growing broilers positively affect growth performance, meat quality, and yields of valuable cuts, although they increase moisture and decrease protein in breast meat, affecting some blood parameters. Implications: This study showed the potential advantages of using PCPM as an alternative food in diets for slow-growing broilers to improve the productivity and health of a sustainable livestock. The challenge of feeding our planet sustainably is more pressing than ever, pushing us to find smarter ways to use available resources. This study looked at using Paullinia cupana peel meal (PCPM) as a new ingredient in the feed of slow-growing broilers. The research found that adding PCPM improved the growth and health of slow-growing broilers, suggesting that it could be a game-changer in sustainable livestock farming. [ABSTRACT FROM AUTHOR]

Duck hatchery waste is an alternative feed ingredient for protein sources in poultry. This study aimed to determine the effect of duck hatchery waste supplementation on growth performance, and income over feed cost of hybrid ducks. A total of 120-day-old male hybrid ducks (body weight: 61.4±4.9g) were randomly divided into three treatments (4 replicates per treatment, 10 ducks per replicate). At 0-14 days of age, ducks were fed the same complete feed in all treatments. After 14 days of age, ducks were fed an experimental diet until 35 days of age. The treatment feed consists of a basal diet (P0), basal diet with 8% hatchery waste (P1), and basal diet with 16% hatchery waste (P2). Supplementation of 8% and 16% duck hatchery waste increased accumulated feed consumption and body weight gain of hybrid ducks on day 35 (P<0.05). However, feeding duck hatchery waste did not affect the feed conversion ratio of hybrid ducks on week 5. In contrast, supplementation of duck hatchery waste decreased the FCR of hybrid ducks at weeks 3 and 4. Furthermore, the inclusion of duck hatchery waste in the duck diet increased revenue generation from duck sales and increased the IOFC value. In conclusion, supplementation of duck hatchery waste can increase feed intake and body weight gain, duck sales and IOFC value of hybrid ducks. [ABSTRACT FROM AUTHOR]

Background: Feed costs account for a high proportion of the variable cost of beef production, ultimately impacting overall profitability. Thus, improving feed efficiency of beef cattle, by way of determining the underlying genomic control and selecting for feed efficient cattle provides a method through which feed input costs may be reduced whilst also contributing to the environmental sustainability of beef production. The rumen microbiome dictates the feed degradation capacity and consequent nutrient supply in ruminants, thus potentially impacted by feed efficiency phenotype. Equally, liver tissue has been shown to be responsive to feed efficiency phenotype as well as dietary intake. However, although both the rumen microbiome and liver transcriptome have been shown to be impacted by host feed efficiency phenotype, knowledge of the interaction between the rumen microbiome and other peripheral tissues within the body, including the liver is lacking. Thus, the objective of this study was to compare two contrasting breed types (Charolais and Holstein-Friesian) divergent for residual feed intake (RFI) over contrasting dietary phases (zero-grazed grass and high-concentrate), based on gene co-expression network analysis of liver transcriptome data and microbe co-abundance network of rumen microbiome data. Traits including RFI, dry matter intake (DMI) and growth rate (ADG), as well as rumen concentrations of volatile fatty acids were also included within the network analysis. Results: Overall, DMI had the greatest number of connections followed by RFI, with ADG displaying the fewest number of significant connections. Hepatic genes related to lipid metabolism were correlated to both RFI and DMI phenotypes, whilst genes related to immune response were correlated to DMI. Despite the known relationship between RFI and DMI, the same microbes were not directly connected to these phenotypes, the Succiniclasticum genus was however, negatively connected to both RFI and ADG. Additionally, a stepwise regression analysis revealed significant roles for both Succiniclasticum genus and Roseburia.faecis sp. in predicting RFI, DMI and ADG. Conclusions: Results from this study highlight the interactive relationships between rumen microbiome and hepatic transcriptome data of cattle divergent for RFI, whilst also increasing our understanding of the underlying biology of both DMI and ADG in beef cattle. [ABSTRACT FROM AUTHOR]

Genetic selection for feed efficiency is possible in Holstein dairy cattle. However, measuring individual cow feed intake is expensive, which limits available phenotypes, resulting in lower prediction accuracy of breeding values than desired. New indicator trait phenotypes for feed efficiency could help improve breeding value accuracies if they can be measured widely across dairy herds. The objective of this study was to identify milk metabolites associated with feed intake and efficiency traits that may serve as new indicator traits. Metabolites were obtained from three sources and two distinct groups of cows. Gas chromatography mass spectrometry (GC-MS), and liquid chromatography mass spectrometry (LC-MS) assays were conducted on a subset of 39 cows identified based on their extreme residual feed intake (RFI; top and bottom 15%). Routinely collected on-farm milk testing data were evaluated on a second, larger subset of 357 cows. Statistical models were created to evaluate if metabolites: 1) provided novel feed efficiency information; 2) served as proxies for body weight traits not routinely collected on farms; and 3) were associated with breeding values for feed efficiency traits, including: predicted transmitting abilities (PTA) for feed saved (FS), RFI and body weight composite (BWC). Ontology enrichment analysis was used to identify enriched pathways from the contrast of extreme RFI cows by GC-MS and LC-MS. The false discovery rate (FDR, reported as q-values) and Hommel corrections were used as multiple testing corrections. Partial least squares discriminate analysis confirmed animals could be classified as high or low feed efficiency groups. A total of 33 GC-MS metabolites, 10 LC-MS ontology pathways (both q<0.20) and 42 fatty acid or milk quality assays from on-farm tests (Hommel adj-p<0.05) were identified for analyses 1, 2, and 3 respectively. Ontology enrichment analysis of LCMS data identified the sphingolipid metabolism (analysis 2), and beta-alanine metabolism (analysis 1) pathways (q<0.20). Heptanoic acid was identified as associated with PTA BWC (GC-MS, Model 3; q<0.15). These metabolites represent new candidate indicator traits for feed efficiency that could be included in existing on-farm milk testing systems upon validation. [ABSTRACT FROM AUTHOR]

Simple Summary: Prolonged stress negatively affects pig health, welfare, and productivity. Herein, we used a porcine model of stress during the growing period, divided into stressed and control groups. Stressed pigs experienced reduced space and were mixed twice, leading to decreased body weight and feed efficiency. Differences in feeding behavior were also observed; stressed pigs visited feeders less frequently and spent more time per meal. The microbiota of stressed pigs showed an increase in opportunistic bacteria, while control pigs had a higher abundance of beneficial butyrate- and propionate-producing bacteria. This study highlights the potential of using specific fecal microorganisms as non-invasive biomarkers to assess stress and well-being in pigs, with implications for improving both animal welfare and research applied to the human gut-brain axis. Stress significantly affects the health, welfare, and productivity of farm animals. We performed a longitudinal study to evaluate stress's effects on pig performance, feeding behavior, and fecal microbiota composition. This study involved 64 Duroc pigs during the fattening period, divided into two experimental groups: a stress group (n = 32) and a control group (n = 32). Stressed groups had less space and were mixed twice during the experiment. We monitored body weight, feed efficiency, feeding behavior, and fecal microbiota composition. Compared to the control group, the stressed pigs exhibited reduced body weight, feed efficiency, fewer feeder visits, and longer meal durations. In the fecal microbiota, resilience was observed, with greater differences between groups when sampling was closer to the stressful stimulus. Stressed pigs showed an increase in opportunistic bacteria, such as Streptococcus, Treponema and members of the Erysipelotrichaceae family, while control pigs had more butyrate- and propionate-producing genera like Anaerobutyricum, Coprococcus and HUN007. Our findings confirm that prolonged stress negatively impacts porcine welfare, behavior, and performance, and alters their gut microbiota. Specific microorganisms identified could serve as non-invasive biomarkers for stress, potentially informing both animal welfare and similar gut-brain axis mechanisms relevant to human research. [ABSTRACT FROM AUTHOR]

Background: Feed efficiency is a crucial economic trait in poultry industry. Both host genetics and gut microbiota influence feed efficiency. However, the associations between gut microbiota and host genetics, as well as their combined contributions to feed efficiency in laying hens during the late laying period, remain largely unclear. Methods: In total, 686 laying hens were used for whole-genome resequencing and liver transcriptome sequencing. 16S rRNA gene sequencing was conducted on gut chyme (duodenum, jejunum, ileum, and cecum) and fecal samples from 705 individuals. Bioinformatic analysis was performed by integrating the genome, transcriptome, and microbiome to screen for key genetic variations, genes, and gut microbiota associated with feed efficiency. Results: The heritability of feed conversion ratio (FCR) and residual feed intake (RFI) was determined to be 0.28 and 0.48, respectively. The ileal and fecal microbiota accounted for 15% and 10% of the FCR variance, while the jejunal, cecal, and fecal microbiota accounted for 20%, 11%, and 10% of the RFI variance. Through SMR analysis based on summary data from liver eQTL mapping and GWAS, we further identified four protein-coding genes, SUCLA2, TNFSF13B, SERTM1, and MARVELD3, that influence feed efficiency in laying hens. The SUCLA2 and TNFSF13B genes were significantly associated with SNP 1:25664581 and SNP rs312433097, respectively. SERTM1 showed significant associations with rs730958360 and 1:33542680 and is a potential causal gene associated with the abundance of Corynebacteriaceae in feces. MARVELD3 was significantly associated with the 1:135348198 and was significantly correlated with the abundance of Enterococcus in ileum. Specifically, a lower abundance of Enterococcus in ileum and a higher abundance of Corynebacteriaceae in feces were associated with better feed efficiency. Conclusions: This study confirms that both host genetics and gut microbiota can drive variations in feed efficiency. A small portion of the gut microbiota often interacts with host genes, collectively enhancing feed efficiency. Therefore, targeting both the gut microbiota and host genetic variation by supporting more efficient taxa and selective breeding could improve feed efficiency in laying hens during the late laying period. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the impact of supplementing sodium bicarbonate or a commercial blend of buffering agents (BBA) comprising calcareous calcitic, magnesium oxide, calcareous algae, and sodium bicarbonate on the productive, behavioral and metabolic parameters of Holstein cows fed starchy diets. Over a 60-day trial period, thirty-six multiparous cows with an average milk yield of 38.84 ± 9.24 kg/day and 63.74 ± 18.63 days in milk (DIM), were randomly divided into two groups. The control group (n = 18) received a supplementation of 1.1% dry matter (DM) of sodium bicarbonate (Raudi®, Totalmix, Brazil), while the BBA group (n = 18) was administered with 0.5% DM of a blend of buffering agents (Equalizer®, Nutron/Cargill, Brazil). The mean values of ruminal pH (control 6.80 ± 0.06 and BBA 6.77 ± 0.06; P > 0.05) and volatile fatty acid (VFA) production (control: acetate 62.63 ± 1.29%, propionate 22.99 ± 1.07%, butyrate 14.30 ± 0.52%; BBA: acetate 63.07 ± 1.32%, propionate 23.47 ± 1.10%, butyrate 13.70 ± 0.57%), were similar (P > 0,05) between the two groups. The value of faecal pH was higher (P < 0.05) in the BBA group (6.25 ± 0.02) than the control group (6.12 ± 0.02). Animals treated with BBA exhibited lower (P < 0,05) dry matter intake (DMI) (24.75 ± 0.64 kg/day), higher feed efficiency (FE) (1.64 ± 0.03), and reduced feeding frequency (52.89 ± 3.73 n°/day) than the control group (DMI, 26.75 ± 0.62 kg/day; FE, 1.50 ± 0.03; feeding frequency, 66.07 ± 3.64 n°/day). Milk production remained similar across both groups (control, 39.11 ± 0.92 kg/day and BBA, 39.87 ± 0.92 kg/day; P > 0.05). Notably, the control group displayed a higher (P < 0,05) concentration of milk protein (1.21 ± 0.05 kg/day) than the BBA (1.18 ± 0.05 kg/day) group. The study concluded that both treatments effectively buffered the rumen and mitigated the risk of ruminal acidosis. Moreover, the higher faecal pH in the BBA-treated group suggests potential intestinal action attributable to the synergistic effects of diverse additives with buffering properties. Despite a reduced DMI, BBA-treated animals exhibited improved FE. [ABSTRACT FROM AUTHOR]

The presence of complex microorganisms in the rumen of ruminants are able to process the lignocellulose from low quality feed and fodder into volatile fatty acids, convert non-protein nitrogen into microbial protein and synthesize B vitamins, thus, ruminants are able to produce food of animal origin without competition for feed with non-ruminants and man. On the other hand, they contribute 14 per cent of anthropogenic methane, released annually into the atmosphere. Manipulating the rumen microbiome is considered as an important approach to reduce environmental impact, while increasing production efficiency in ruminants. A systematic literature search was undertaken and relevant research and review articles were downloaded, classified and salient points extracted to prepare the narrative review on "Influence of Feed and Feeding strategies on Rumen microbiome". The microbial community in the rumen is the most diverse composed of bacteria, archaea, protozoa, fungi and uncharacterized virome. Differences in ruminal microbial community compositions are predominantly attributable to diet. Dietary manipulation offers a viable solution to alter the rumen microbiome so that the present-day challenges faced by the ruminant livestock industry is addressed. [ABSTRACT FROM AUTHOR]

Objective: This study investigated the repeatability of feed efficiency and its association with carcass traits in Hanwoo steers during the entire growing and fattening periods. Methods: The growth and intake of thirty-six Hanwoo steers (259±19.7 kg; nine months) were monitored throughout five periods, including two growing periods (GP) and three fattening periods (FP). The steers were fed two types of concentrate mixes with varying nutrient compositions until they reached a target weight of 800 kg for slaughter. For each period, steers were categorized into three classes based on their feed efficiency rankings using residual feed intake (RFI) and feed conversion ratio (FCR). Feed efficiency repeatability was assessed using the Spearman correlation coefficient, decomposition of random errors, and the Theil segregation index (TSI). The Pearson correlation coefficient was used to examine the relationship between feed efficiency and carcass traits. Results: The results demonstrated a significant and high correlation with RFI, but not FCR, during the growing or fattening stages (r>0.5; p<0.01). When steers were classified according to their feed efficiency rankings, 58% of the animals in the high RFI class (low efficient) initially (GP 1) remained in the same class by the last period (FP 3), whereas steers were randomly distributed based on FCR. The repeatability, assessed by the decomposition of random errors, was higher for RFI (0.61) than for FCR (0.15). The TSI also indicated that RFI rankings, rather than FCR rankings, are more likely to be maintained. Moreover, a weak association was observed between feed efficiency and carcass traits. Conclusion: In conclusion, RFI repeatability throughout the GP and FP surpassed that of the FCR, with steers classified as high RFI during the GP more likely to remain in the same class during the FP. Feed efficiency was weakly correlated with carcass traits. [ABSTRACT FROM AUTHOR]

This study aimed to assess the effect of dietary supplementation of a mixture of botanical compounds and essential oil (Phyto AquaMeric, PAM) on the growth, immune and antioxidant parameters and environmental benefits in Nile tilapia. Two diets including a control and a PAM-supplemented diet at 0.5 g kg−1 were prepared for the trial. The diets were isonitrogenous (30% crude protein) and isoenergetic (17 MJ kg−1) extruded diets. Nile tilapia weighing initially 74.22 ± 1.96 g fish−1 were stocked in 2 m3 hapas at a density of 20 fish per m3 (40 fish per hapa). Each group was tested in triplicates over 80 days. The antioxidant potential of PAM was compared to vitamin C through KRL test, showing a higher value from 35 to 100 mg. The in vivo trial did not exhibit any significant growth performance improvement. However, the PAM group had a significantly improved feed conversion ratio (FCR) and protein efficiency ratio (PER). Moreover, the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), Malondialdehyde (MDA), immune parameters (ACH50, lysozyme, phagocytic and phenoloxidase activities), digestive enzymes and hepatic enzymes were significantly improved in the PAM-fed group. An evaluation of eutrophication potential of PAM supplementation revealed a low input in the system. In conclusion, this mixture of botanicals and essential oil exhibited in vitro and in vivo antioxidant potential, improved health and digestive parameters and contributed to a reduced eutrophication risk in the tilapia production system. [ABSTRACT FROM AUTHOR]

We utilized plasma proteomics profiling to explore metabolic pathways and key proteins associated with divergent residual body weight gain (RADG) phenotype in crossbred (Angus × Hereford) beef steers. A group of 108 crossbred growing beef steers (average BW = 282.87 ± 30 kg; age = 253 ± 28 days) were fed a highforage total mixed ration for 49 days in five dry lot pens (20-22 beef steers per pen), each equipped with two GrowSafe8000 intake nodes to determine their RADG phenotype. After RADG identification, blood samples were collected from the beef steers with the highest RADG (most efficient; n = 15; 0.76 kg/d) and lowest RADG (least efficient; n = 15; -0.65 kg/d). Plasma proteomics analysis was conducted on all plasma samples using a nano LC-MS/MS platform. Proteins with FC = 1.2 and false-discovery rate-adjusted p-values (FDR) = 0.05 were considered significantly differentially abundant. The analysis identified 435 proteins, with 59 differentially abundant proteins (DAPs) between positive and negative-RADG beef steers. Plasma abundance of 38 proteins, such as macrophage stimulating 1 and peptidase D was upregulated (FC = 1.2, FDR = 0.05) in positive-RADG beef steers, while 21 proteins, including fibronectin and ALB protein were greater (FC < 1.2, FDR = 0.05) in negative-RADG beef steers. The results of the Gene Ontology (GO) analysis of all the DAPs showed enrichment of pathways such as metabolic processes, biological regulation, and catalytic activity in positive-RADG beef steers. Results of the EuKaryotic Orthologous Groups (KOG) analysis revealed increased abundance of DAPs involved in energy production and conversion, amino acid transport and metabolism, and lipid transport and metabolism in positive-RADG beef steers. The results of this study revealed key metabolic pathways and proteins associated with divergent RADG phenotype in beef cattle which give more insight into the biological basis of feed efficiency in crossbred beef cattle. [ABSTRACT FROM AUTHOR]

Abstract: Optimizing feed efficiency through the feed conversion ratio (FCR) is paramount for economic viability and sustainability. In this study, we integrated RNA-seq, ATAC-seq, and genome-wide association study (GWAS) data to investigate key functional variants associated with feed efficiency in pigs. Identification of differentially expressed genes in the duodenal and muscle tissues of low- and high-FCR pigs revealed that pathways related to digestion of dietary carbohydrate are responsible for differences in feed efficiency between individuals. Differential open chromatin regions identified by ATAC-seq were linked to genes involved in glycolytic and fatty acid processes. GWAS identified 211 significant single-nucleotide polymorphisms associated with feed efficiency traits, with candidate genes PPP1R14C, TH, and CTSD. Integration of duodenal ATAC-seq data and GWAS data identified six key functional variants, particularly in the 1500985–1509676 region on chromosome 2. In those regions, CTSD was found to be highly expressed in the duodenal tissues of pigs with a high feed conversion ratio, suggesting its role as a potential target gene. Overall, the integration of multi-omics data provided insights into the genetic basis of feed efficiency, offering valuable information for breeding more efficient pig breeds. [ABSTRACT FROM AUTHOR]

Aquaculture production is continuously increasing, consequently increasing the demand for feed. Unfortunately, the reliance on fish meal and fish oil also raises sustainability issues due to overfishing and resource depletion. Nanoparticle-enhanced feed presents a promising solution to these challenges. Nanoparticles, with their large surface area-to-volume ratio and encapsulation capabilities, significantly improve nutrient delivery, absorption, and utilization, enhancing growth and health. Their immune-modulatory and antimicrobial properties reduce antibiotic use and support sustainability. This review explores different nanoparticles in fish feed, including metal-based, non-metal-based, and composite types, each offering benefits for fish growth and health. It highlights the advantages of nanoparticle-enhanced feed, such as improved nutrient delivery, immune enhancement, antimicrobial action, stress reduction, and environmental sustainability. Concerns like potential toxicity, safety, bioaccumulation, and environmental impacts of nanoparticles, together with measures of addressing these concerns, are also highlighted. The review concludes with insights into future research directions. [ABSTRACT FROM AUTHOR]

The recent chromosome-based genome assembly and the newly developed 70K single nucleotide polymorphism (SNP) array for American mink (Neogale vison) facilitate the identification of genetic variants underlying complex traits in this species. The objective of this study was to evaluate the association between consensus runs of homozygosity (ROH) with growth and feed efficiency traits in American mink. A subsample of two mink populations (n = 2,986) were genotyped using the Affymetrix Mink 70K SNP array. The identified ROH segments were included simultaneously, concatenated into consensus regions, and the ROH-based association studies were carried out with linear mixed models considering a genomic relationship matrix for 11 growth and feed efficiency traits implemented in ASReml-R version 4. In total, 298,313 ROH were identified across all individuals, with an average length and coverage of 4.16 Mb and 414.8 Mb, respectively. After merging ROH segments, 196 consensus ROH regions were detected and used for genome-wide ROH-based association analysis. Thirteen consensus ROH regions were significantly (P < 0.01) associated with growth and feed efficiency traits. Several candidate genes within the significant regions are known for their involvement in growth and body size development, including MEF2A, ADAMTS17, POU3F2, and TYRO3. In addition, we found ten consensus ROH regions, defined as ROH islands, with frequencies over 80% of the population. These islands harbored 12 annotated genes, some of which were related to immune system processes such as DTX3L, PARP9, PARP14, CD86, and HCLS1. This is the first study to explore the associations between homozygous regions with growth and feed efficiency traits in American mink. Our findings shed the light on the effects of homozygosity in the mink genome on growth and feed efficiency traits, that can be utilized in developing a sustainable breeding program for mink. [ABSTRACT FROM AUTHOR]

Introduction The beginning of lactation is one of the important performance signs related to health, fertility and production in lactating cows. Meeting the energy needs is considered as the main challenge of lactating cows at this period. Increasing the mobilization of body fat is one of the ways to meet the lack of energy, which can lead to an increase in the supply of non-esterified fatty acids (NEFA). Therefore, management strategies based on nutrition can play an important role in increasing energy intake and minimizing negative energy balance (NEB). The use of fat supplements can be considered as an effective solution to increase the amount of energy in the diets of fresh cows. The objective of this study was to evaluate the effect of feeding different fat supplements containing saturated and unsaturated fatty acids on production performance, blood and rumen parameters in fresh Holstein cows. Materials and Methods In this study, 32 Holstein cows with average live body weight 649.2 ± 29.11 kg and body condition score of 3.78 ± 0.30 were used after calving for 21 days in a completely randomized design in four experimental groups. Experimental treatments included: 1) control: no fat supplement, 2) unsaturated: containing calcium salt of unsaturated fatty acids, three percent based on DM, 3) saturated: containing calcium salt of saturated fatty acids, three percentage based on DM and 4) mixed: contained an equal mixture of both types of fat supplements. Dry matter intake (DMI) was measured daily. Cows were milked three times a day at 05:00, 13:00 and 21:00 in a parlor and milk yield was recorded. Milk was sampled at each milking on days 7, 14 and 21 until analyzed for fat. Body weight was measured on days 7, 14 and 21 after parturition. Blood samples were collected from subcaudal vein with vacuum tubes containing anticoagulant heparin on days 0, 7 and 21 after parturition. After separating the serum using a centrifuge, for the measurement of glucose, triglyceride, cholesterol, NEFA and beta-hydroxybutyrate (BHBA), samples were sent to the laboratory. Ruminal fluid is collected on the d 21 after parturition, two to three hours after morning feeding by the esophageal tube and using a suction pump, and after passing through the filter and measuring the pH by a portable pH meter, was sent to the laboratory to measure volatile fatty acids (VFA). Results and Discussion The results of the study showed that the calcium salt of unsaturated fatty acids caused a decrease, and the calcium salt of saturated and mixed fatty acids caused an increase in DMI compared to the control treatment. Milk production, milk fat percentage, 4% fat corrected milk production, energy corrected milk production, feed efficiency, blood concentrations of glucose, cholesterol, triglyceride and BHBA values, as well as rumen fermentation parameters were not affected by the treatments. The concentration of NEFA in the plasma, in the control treatment and the treatment containing calcium salts of unsaturated fatty acids, were measured above the safety margin provided for sub clinical ketosis. Conclusion According to the lactation performance of cows, the absence of problems regarding the amounts of NEFA and BHBA as indicators of metabolic disorders and the ineffectiveness of supplements on rumen fermentation parameters, it seems that it is possible to use an equal mixture (50:50) of fat supplements of calcium salts containing saturated and unsaturated fatty acids in the diet of fresh dairy cows in the amount of three percent. [ABSTRACT FROM AUTHOR]

This meta-analysis aims to investigate the effects of residual feed intake (RFI) phenotype on performance, nutrient utilization and meat quality traits in Zebu (Bos indicus) cattle. Twenty-three peer-reviewed publications with 37 treatment means were included in the dataset. Weighted mean difference analysis compared animals categorized into low RFI (more efficient) versus medium or high RFI (less efficient) groups. Data heterogeneity via meta-regression and subgroup analysis, considering variables such as animal age, sex class, experimental duration, RFI group, dietary concentrate, and estimated metabolizable energy intake were also explored. The predominant genetic group of cattle in the dataset was Nellore (89.18%), followed by Brahman (10.81%). More efficient animals (low RFI phenotype) exhibited less dry matter intake (DMI; P < 0.010) than medium or high RFI animals (-0.95 kg vs. -0.42 kg/d). Cattle dietary crude protein and fiber digestibility were consistent across RFI groups (P > 0.05), while dietary ether extract digestibility tended to decrease (P = 0.050) in low RFI animals (-13.20 g/kg DM). Low RFI animals tended to increased (P = 0.065) ribeye area (REA) compared to the high/medium RFI groups, while carcass backfat thickness (BFT) decreased (P = 0.042) compared to high/medium RFI groups. Moreover, there was an increase (P < 0.001) of 0.22 kg in Warner-Bratzler shear force (WBSF) and a reduction (P < 0.001) in the myofibrillar fragmentation index (MFI) in low RFI animals. Meat color parameters (lightness [L*] and yellowness [b*]) and visual marbling scores were consistent (P > 0.05) across RFI groups. In conclusion, Zebu cattle classified as efficient (low RFI) exhibited reduced DMI, which improves their feed efficiency. However, BFT and meat quality parameters such as tenderness (WBSF and MFI) and redness [a*] were compromised by low RFI phenotype, highlighting the challenge of enhancing feed efficiency and meat quality traits in Zebu cattle. [ABSTRACT FROM AUTHOR]

Simple Summary: Intensively managing the use of concentrate supplementation to complement nutrition can increase production costs and reduce producers' income. Considering the frequently large price fluctuations for soybean meal, an alternative is the replacement of local protein sources in ruminant feeding. In this study, we compared the effects of different sources of protein (soybean meal, cottonseed meal, peanut meal, rapeseed meal, and distillers' dried grains with solubles) on the growth, digestibility, and rumen fermentation of growing lambs. Our results showed that when soybean meal was totally replaced with either cottonseed meal, peanut meal, rapeseed meal, or distillers' dried grains with solubles, there was no impact on the average daily gain of growing lambs, but digestibility was reduced. Our study provides a theoretical basis for the rational selection and utilization of proteins from different sources, which helps us to optimize the feeding management of growing lambs. Considering the frequently large price fluctuations for soybean meal, an alternative is the increased use of locally produced high-protein ingredients. The objective of this study was to evaluate the effects of the total replacement of soybean meal with different sources of protein on the growth performance, nutrient digestibility, serum parameters, rumen fermentation parameters, and bacterial communities in growing lambs. Sixty sheep with similar body weights (38.46 ± 0.71 kg) were distributed to one of five treatments: soybean meal (SBM); cottonseed meal (COM); peanut meal (PEM); rapeseed meal (RAM); and distillers' dried grains with solubles (DDGS). The experiment lasted 62 days with a 10-day adaptation period and a 52-day growing period. The results indicated that the body weight and average daily gain were not affected by different protein sources (p > 0.05), but the dry matter intake of the SBM group was lower than that of the other groups (p < 0.05); otherwise, the feed efficiency was higher (p < 0.05). The digestion of dry matter was higher in the SBM, COM, and RAM groups than in the DDGS and PEM groups (p < 0.05). Meanwhile, compared to the other groups, the SBM group had the highest digestion of gross energy and crude protein (p < 0.05). In addition, the concentration of glutathione peroxidase was highest in the SBM group (p < 0.05). Regarding the rumen fermentation, the SBM group had the highest concentration of NH3-N (p < 0.05). The rumen bacterial community was not affected by treatments (p > 0.05). In conclusion, the total replacement of soybean meal with cottonseed, peanut, rapeseed, or DDGS reduced digestibility but did not impact the body weight or average daily gain of growing lambs and had no effect on the immune function and rumen bacterial community; thus, they can be used to substitute the soybean meal. [ABSTRACT FROM AUTHOR]

This study's objective was to compare two options of pasture supplementation: corn silage (CS) alone or corn silage mixed with protein concentrate. The experiment was conducted with 18 lactating Holstein cows in mid‐lactation in a crossover design that included three treatments and three data collection periods. All cows had access to pasture for 17 h/day with an average herbage allowance of 16 kg dry matter (DM)/cow/day and were offered in‐barn corn silage, corn silage mixed with protein concentrate, or no supplementation. Cows were equipped with pH sensors residing in the reticulum and, during the 7‐day data collection periods, with a jaw movement recorder. Nonsupplemented cows produced 21.3 kg energy‐corrected milk (ECM) and ate 13.3 kg DM herbage at pasture. Cows supplemented with corn silage and corn silage plus protein produced 2.5 and 4.5 kg/day more ECM, respectively, consumed 3.4 and 3.3 kg/day more DM in total, respectively, ate for a shorter period of time, and ruminated longer than their nonsupplemented peers. Supplemented cows were almost able to cover their energy requirements and mobilised less body mass in contrast to the nonsupplemented cows. Cows offered corn silage plus protein showed increased ECM production, increased milk urea content and lower nitrogen use efficiency (NUE) compared to cows supplemented with corn silage only. Nonsupplemented dairy cows had the highest milk urea content and performed worst in terms of NUE. The best feed conversion efficiency resulted from the nonsupplemented dairy cows and those supplemented with corn silage plus protein. In nonsupplemented cows, the high feed conversion efficiency seemed to be due to the increased mobilisation of body mass. As a result of the starch‐rich supplementations, the ruminal acetic:propionic acid ratio became smaller, and the proportions of n‐butyric acid increased. The mean reticular pH values did not substantially vary across the three feeding treatments. For the choice of a supplementation option, herbage allowance and cost of supplement will have to be considered, but aspects of feed–food competition as well as animal welfare should not be ignored. [ABSTRACT FROM AUTHOR]

A feeding trial was carried out to investigate the effects of a dietary fermented poultry by-product (FPBP) on the growth performance, feed efficiency, body chemical composition, blood biochemical tests and economic efficiency of the Nile tilapia, Oreochromis niloticus fingerlings. Poultry by-product was subjected to solid-state fermentation then incorporated into four experimental (Isonitrogenous 30% and iso-caloric 4400Kcal/ Kg) diets containing 0, 25, 50 and 75% FPBP instead of soybean meal. Results revealed that the replacement of soybean meal with FBPP had significantly high (P≤ 0.05) growth performance and feed utilization. Moreover, body ash content decreased insignificantly (P≤ 0.05) compared to the control. At a low substitution level of 25% FPBP, a significant increase in body fat content (P≤ 0.05) was recorded compared to the control. Furthermore, body ash and energy contents demonstrated a significant increase (P≤ 0.05) compared with the control. Additionally, biochemical blood tests revealed that FPBP does not have any harmful effects on either liver or kidney function parameters. It could be concluded that the replacement of soybean meal with FPBP at a level of 25% was the best in terms of growth performance and feed utilization under these experimental conditions. [ABSTRACT FROM AUTHOR]

Feed efficiency (FE) is essential for pig production, has been reported to be partially explained by gut microbiota. Despite an extensive body of research literature to this topic, studies regarding the regulation of feed efficiency by gut microbiota remain fragmented and mostly confined to disorganized or semi-structured unrestricted texts. Meanwhile, structured databases for microbiota analysis are available, yet they often lack a comprehensive understanding of the associated biological processes. Therefore, we have devised an approach to construct a comprehensive knowledge graph by combining unstructured textual intelligence with structured database information and applied it to investigate the relationship between pig gut microbes and FE. Firstly, we created the pgmReading knowledge base and the domain ontology of pig gut microbiota by annotating, extracting, and integrating semantic information from 157 scientific publications. Secondly, we created the pgmPubtator by utilizing PubTator to expand the semantic information related to microbiota. Thirdly, we created the pgmDatabase by mapping and combining the ADDAGMA, gutMGene, and KEGG databases based on the ontology. These three knowledge bases were integrated to form the Pig Gut Microbial Knowledge Graph (PGMKG). Additionally, we created five biological query cases to validate the performance of PGMKG. These cases not only allow us to identify microbes with the most significant impact on FE but also provide insights into the metabolites produced by these microbes and the associated metabolic pathways. This study introduces PGMKG, mapping key microbes in pig feed efficiency and guiding microbiota-targeted optimization. [ABSTRACT FROM AUTHOR]

The genetic trait of residual feed intake (RFI) holds considerable importance in the swine industry. Recent research indicates that the gut microbiota of pigs plays a pivotal role in the manifestation of the RFI trait. Nevertheless, the metabolic pathways involved in the functioning of these microorganisms remain elusive. Thus, based on the ranking of the RFI trait in Duroc pigs, the present study selected the top 10 and bottom 10 pigs as the experimental subjects. The distribution and metabolite differences of cecal microbiota were analyzed using 16S rRNA gene sequencing and liquid chromatography--tandem mass spectrometry (LC--MS/MS) techniques. The low RFI cecal group was named LRC, and the high RFI cecal group was named HRC. The results indicate that the LRC group had lower RFI, feed conversion ratio (FCR), average daily feed intake (ADFI) (p < 0.001), and thinner backfat (p < 0.05) compared with the HRC group. We simultaneously recorded the foraging behavior as well, the LRC group had a significant increase in total time spent at the feeder per day (TPD) (p < 0.05) and a significant increase in average feed intake per mins (AFI) and the number of visits to the feeder per day (NVD) compared to the HRC group (p < 0.001). Clostridium_XVIII, Bulleidia, and Intestinimonas were significantly enriched in the LRC group (p < 0.01), while Sutterella, Fusobacterium, and Bacteroides were significantly increased in the HRC group (p < 0.01). In the metabolome, we detected 390 (248 metabolites up and 142 down in the LRC compared with HRC), and 200 (97 metabolites up and 103 down in the LRC compared with HRC) differential metabolites in positive and negative ionization modes. The comprehensive analysis found that in the LRC group, Escherichia and Eubacterium in the gut may increase serotonin content, respectively. Bacteroides may deplete serotonin. We suggest that the RFI may be partly achieved through tryptophan metabolism in gut microbes. In individuals with low RFI, gut microbes may enhance feed efficiency by enhancing host synthesis and metabolism of tryptophan-related metabolites. [ABSTRACT FROM AUTHOR]

"Nano", which derives from the Latin word nanus and means dwarf, refers to a very small unit of measurement equal to one billionth of a meter. Nanotechnology, which deals with the manipulation of matter at the atomic and molecular level, has an application area in animal husbandry as well as in many fields. Nano-sized feed additives, which have come to the forefront in the livestock sector in recent years, have become an innovative application used to increase the nutritional value of feeds and optimize animal health and performance. Since these additives are nano-sized particles with increased specific surface area, they can have a positive effect on a number of factors such as digestibility, nutrient absorption, immune system, growth and development. Minerals in the form of nanoparticles used as feed additives can increase bioavailability by passing through the intestinal wall to body cells faster compared to larger particles. The nano level of the substance not only increases the productivity of animals, but also brings the potential to improve the functionality of feed molecules. Nano feed additives increase the digestion and absorption of feed, allowing animals to benefit from feed more effectively. However, there are several challenges associated with this approach. These include the potential for endotoxin production, reduced nutrient absorption due to interaction with natural nutrients, the possibility of nanoparticle accumulation in the animal body, health risks, ethical considerations, environmental concerns and some negative effects such as interference with natural nutrients that can be avoided by encapsulation. This article discusses recent studies on nano-sized feed additives that offer potential benefits in animal nutrition. [ABSTRACT FROM AUTHOR]

This study focused on exploring the metabolomic profiles of crossbred beef cattle with varying levels of residual feed intake (RFI), a measure of feed efficiency in beef cattle. Sixty-seven crossbred growing beef steers (BW = 277 ± 29.7 kg) were subjected to a high-forage total mixed ration for 64 days to determine their RFI phenotypes. At the end of the 64d feeding trial, beef steers were divided into two groups based on their RFI values: low (or negative)-RFI beef steers (n = 28; RFI = −1.08 ± 0.88 kg/d) and high (or positive)-RFI beef steers (n = 39; RFI = 1.21 ± 0.92 kg/d). Blood samples were collected, and plasma samples were analyzed using Nuclear Magnetic Resonance spectroscopy, resulting in the identification of 50 metabolites. The study found a distinct metabolomic signature associated with RFI status. Eight metabolites, including amino acids (tyrosine, glycine, valine, leucine, and methionine) and other compounds (dimethyl sulfone, 3-hydroxy isovaleric acid, citric acid, creatine, and L-carnitine), showed differential abundance between low- and high-RFI groups. Specifically, tyrosine, glycine, and dimethyl sulfone exhibited significant specificity and sensitivity, which produced a discriminatory model with an area under the receiver operating characteristic (ROC) curve of 0.7, making them potential markers for RFI. A logistic regression model incorporating these biomarkers effectively distinguished between high- and low-RFI steers, with a threshold cutoff point of 0.48, highlighting a distinctive metabolite profile associated with efficient nutrient utilization in low-RFI cattle. The logistic regression model, incorporating these biomarkers, holds promise for accurately categorizing RFI values, providing insights into the metabolic basis of feed efficiency in beef cattle. [ABSTRACT FROM AUTHOR]

This study in dairy cow feeding explored the effects of growth stage and chop length for grass‐clover silage, and of concentrate protein level, including the interactions of these three factors. The experiment was conducted with 48 Norwegian Red cows according to a cyclic change‐over design with four 4‐week experimental periods and eight dietary treatments in a 2 × 2 × 2 factorial arrangement. Round bale silage from a mixed sward of timothy, meadow fescue, and red clover was harvested at two growth stages (H1, H2) and offered to dairy cows either unchopped with median particle length of 152 mm or chopped to 19 mm median particle length before feeding. A low protein (LP) concentrate containing 7% lignosulphonate treated soybean meal (SBM) and a high protein (HP) concentrate containing 12% solvent extracted SBM were compared. Silage was offered ad libitum and supplemented with 8 kg concentrate per day. Silage dry matter intake was 2.0 kg higher for H1 than H2 silage, which supported a higher yield of milk, energy‐corrected milk and the milk constituents, fat, protein, and lactose. All these measures of milk production, as well as feed energy efficiency and N use efficiency, increased when silage was fed chopped rather than unchopped. Lignosulphonate treated SBM spared N in the diet without milk yield reductions. For efficient milk production with high energy and N utilisation, we recommend chopping to 20 mm for timothy, meadow fescue, and clover silages harvested in late stem elongation or in reproductive growth stages. [ABSTRACT FROM AUTHOR]

The inclusion of fibrolytic enzymes in the diet is believed to have positive effects on animal production. Hence, the objective of this study was to investigate the impact of supplementing diets with a commercial fibrolytic enzyme preparation (Vistamax; mixture of xylanase and cellulase) derived from Trichoderma reesei on lactational performance, digestibility, and plasma nutrient levels in high-producing dairy cows. Two dietary energy levels were considered: a normal energy diet (metabolizable energy = 2.68 Mcal/kg) and a slightly lower energy diet (metabolizable energy = 2.55 Mcal/kg). A total of 120 lactating Holstein cows (parity = 2; Days in Milk = 113 ± 23) were randomly assigned to four treatment groups using a 2 * 2 factorial arrangement. The dietary treatments consisted of: (1) normal energy diet without enzyme supplementation (NL); (2) normal energy diet with enzyme supplementation (NLE); (3) slightly lower energy diet without enzyme supplementation (SL); and (4) slightly lower energy diet with enzyme supplementation (SLE). The amount of enzyme added to the diets was determined based on previous in vitro studies and supplier recommendations. The enzyme and premix were mixed prior to the preparation of the total mixed ration, and the trial lasted for a duration of 42 days. The results indicated that the application of the fibrolytic enzyme did not have a significant effect on dry matter intake (DMI), but it did enhance the digestibility of dry matter (DM), neutral detergent fiber (NDF), potentially digestible NDF (pdNDF), organic matter (OM), milk production, milk urea nitrogen (MUN), and blood urea nitrogen (BUN). On the other hand, the slightly lower energy diet resulted in a decrease in DMI, milk production, milk protein yield, plasma free amino acids (FAA), and an increase in plasma B-hydroxybutyrate (BHBA). In conclusion, the inclusion of the fibrolytic enzyme in the diets of dairy cows led to improvements in the digestibility of DM, NDF, pdNDF, OM, milk production, and feed efficiency. Furthermore, the application of the enzyme to the slightly lower energy diet resulted in milk production levels comparable to those observed in cows fed the untreated normal energy diet. [ABSTRACT FROM AUTHOR]

Feed efficiency is a trait of interest in pigs as it contributes to lowering the ecological and economical costs of pig production. A divergent genetic selection experiment from a Large White pig population was performed for 10 generations, leading to pig lines with relatively low-(LRFI) and high- (HRFI) residual feed intake (RFI). Feeding behavior and metabolic differences have been previously reported between the two lines. We hypothesized that part of these differences could be related to differential sensing and absorption of nutrients in the proximal intestine. We investigated the duodenum transcriptome and DNA methylation profiles comparing overnight fasting with ad libitum feeding in LRFI and HRFI pigs (n = 24). We identified 1,106 differentially expressed genes between the two lines, notably affecting pathways of the transmembrane transport activity and related to mitosis or chromosome separation. The LRFI line showed a greater transcriptomic response to feed intake than the HRFI line. Feed intake affected genes from both anabolic and catabolic pathways in the pig duodenum, such as rRNA production and autophagy. Several nutrient transporter and tight junction genes were differentially expressed between lines and/or by short-term feed intake. We also identified 409 differentially methylated regions in the duodenum mucosa between the two lines, while this epigenetic mark was less affected by feeding. Our findings highlighted that the genetic selection for feed efficiency in pigs changed the transcriptome profiles of the duodenum, and notably its response to feed intake, suggesting key roles for this proximal gut segment in mechanisms underlying feed efficiency. [ABSTRACT FROM AUTHOR]

Aquaculture serves as a source of protein and livelihood and is an alternative to capture fisheries, thereby reducing pressure on the wild. However, aquaculture tends to be limited by sustainability issues, which include overdependency on fishmeal, the high cost associated with fishmeal, the environmental impact of aquaculture activities, which may be detrimental to aquatic lives and the environment, and the use of antibiotics to treat diseases, which may have an adverse effect in their host or the environment. Efforts are being made toward attaining practical ways to enhance aquaculture sustainability. One such effort is using functional feed additives in feed formulation. Functional feed additives are dietary ingredients incorporated in feed formulations, not only for the usual provision of basic nutritional requirements as offered by traditional feed but also for growth and health enhancement; environmental and economic gain. This review emphasizes the importance of incorporating functional feed additives such as probiotics, prebiotics, symbiotics, and phytogenics. This study evaluates and presents holistic information on functional additives, their roles in enhancing aquaculture sustainability, and the challenges encountered in their application. [ABSTRACT FROM AUTHOR]

Immune function plays a pivotal role in dictating the overall health and productivity of cattle. In a proficient immune system, the liver assumes an integral function in detoxification and metabolic processes and contributes substantially to overall production and immunity. In this study, we evaluated the hepaticmRNA expression of genes involved in innate and adaptive immunity in crossbred beef steers with positive or negative residual body weight gain (RADG). Positive-RADG beef steers (n = 8; RADG = 0.73 kg/d) and negative-RADG beef steers (n = 8; RADG = -0.69 kg/d) were identified from a group of 108 growing crossbred beef steers (average BW= 556 ± 38 kg) after a 56-d performance testing period. At the end of the 56-d period, liver tissue samples were collected from the beef steers for RNA extraction and cDNA synthesis. The mRNA expression of 84 genes involved in innate and adaptive immunity were analyzed using pathway-focused PCR-based arrays. The mRNA expression of genes with false discovery rate-adjusted P-values (FDR) = 0.05 and absolute fold change (FC) = 1.2 were determined to be differentially expressed. Out of the 84 genes analyzed, four genes (IL-2, MYD88, CD-80, NFkB-1) were differentially expressed and were all upregulated in positive compared with negative-RADG beef steers. IL-2 is a cytokine that plays a critical role in the immune response by activating and proliferating T-cells, which are important for fighting infections. MYD88 is an adaptor protein that is essential for signaling by toll-like receptors, which are involved in pathogen recognition. CD80 is a protein that is expressed on the surface of antigen-presenting cells and plays a critical role in the initiation of an immune response. The activation of NF-kB leads to the production of cytokines and chemokines that help to recruit immune cells to the site of infection. The upregulation of the aforementioned genes in positive-RADG beef steers suggests that they had a better ability than negative-RADG beef steers to quickly recognize pathogens and initiate appropriate responses to effectively fight off infections without causing inflammatory reactions, potentially contributing to their better feed efficiency. [ABSTRACT FROM AUTHOR]

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Simple Summary: The silkworm is an economically important insect, and the popularity of artificial feed has promoted the development of the sericulture industry. However, the improvement of feed efficiency remains a challenge. This study used metabolomics-based methods to analyze the differences in silkworm cocoons and hemolymph between the mulberry-leaf group and the artificial-feed group. It was found that the concentration of amino acids was significantly higher in the mulberry-leaf group than in the artificial-diet group. In a comparison of the effects of different concentrations of valine on silkworms fed the artificial diet, it was found that the food intake of the 2% and 4% valine groups was significantly lower than that of the 0% valine group, but the cocoon-production efficiency was significantly improved. This study demonstrates that valine is an important amino acid that can regulate feed efficiency, providing a new direction for the improvement of artificial feed. Artificial silkworm diets significantly impact farm profitability. Sustainable cocoon production depends on the continuous improvement of feed efficiency to reduce costs and nutrient losses in the feed. This study used metabolomics to explore the differences in silkworm cocoons and hemolymph under two modes of rearing: an artificial diet and a mulberry-leaf diet. Nine metabolites of silkworm cocoons and hemolymph in the mulberry-leaf group were higher than those in the artificial-diet group. Enrichment analysis of the KEGG pathways for these metabolites revealed that they were mainly enriched in the valine, leucine, and isoleucine biosynthesis and degradation pathways. Hence, the artificial silkworm diet was supplemented various concentrations of valine were supplemented to with the aim of examining the impact of valine on their feeding and digestion of the artificial diet. The results indicated that valine addition had no significant effect on feed digestibility in the fifth-instar silkworm. Food intake in the 2% and 4% valine groups was significantly lower than that in the 0% valine group. However, the 2% and 4% valine groups showed significantly improved cocoon-production efficiency, at 11.3% and 25.1% higher, respectively. However, the cocoon-layer-production efficiencies of the 2% and 4% valine groups decreased by 7.7% and 13.9%, respectively. The research confirmed that valine is an effective substance for enhancing the feed efficiency of silkworms. [ABSTRACT FROM AUTHOR]

One of the goals of the breeding program of the Latvian national sheep breed Latvian dark-head (LT; Latvijas tumšgalve) is the improvement of meat productivity, in parallel with good reproduction characteristics. The main part of the costs is the cost of feeding, which can be reduced by raising sheep with high feed efficiency. This goal can be achieved by selecting sheep based on feed efficiency indicators. The fattening data of 100 LT lambs were analysed using the relative growth rate (RGR) and Kleiber's ratio (KR) indicators. The statistical difference was determined between low- and high-efficiency groups by calculating the cost of concentrate feed and income from meat realisation. The difference in the cost of concentrate feed was found after 60-days of intensive fattening and on the day needed for fattening up to 50 kg of live weight of lambs. When calculating the income of lamb meat, the differences between low and high RGR and/or KR efficiency groups were established. Thus, selecting high-ranking RGR and KR sheep can improve the cost and/or income of LT sheep breeders in Latvia. [ABSTRACT FROM AUTHOR]

Context. Improving cattle feed efficiency would reduce feed costs and increase herd profitability. Residual feed intake (RFI) is commonly used to rank cattle for feed efficiency, with low-RFI animals being more efficient than high-RFI animals. However, RFI classification merits further investigation because observed differences in heat energy (HE) production between low- and high-RFI cattle may be related to heat associated with differences in dry-matter intake (DMI) rather than maintenanceenergy requirements. Aims. To determine energy partitioning of beef heifers with low and high residual feed intake. Methods. Angus crossbred heifers (n = 60) were fed a grower diet (metabolisable energy (ME) = 2.17 Mcal/kg DM) for 70 days. Feed intake was recorded daily using the GrowSafe system, and bodyweight (BW) was recorded every 14 days. Residual feed intake was calculated as the residual from the regression of DMI on mid-test BW0.75 and average daily gain (ADG) (R2 = 0.31). Low-RFI (n = 8) and high-RFI (n = 8) heifers were selected for a metabolism experiment to determine energy partitioning at three feed-intake levels, namely, ad libitum intake, and 1.0× and 0.5× expected maintenance-energy requirement. Apparent nutrient digestibility was determined using indigestible neutral detergent fibre (iNDF) as an internal marker. The sulfur hexafluoride (SF6) tracer and oxygen-pulse techniques determined methane emissions and heat production respectively. Metabolisable energy required for maintenance (MEm) and fasting heat production (HeE) were then calculated from the regression of log HP on ME intake (MEI). Efficiencies of ME used for maintenance and growth were calculated from HeE, MEm, and retained energy at ad libitum intake. Key results. Residual feed intake was strongly correlated with DMI (0.83). Low-RFI heifers consumed 31% less (P = 0.01) feed than high-RFI heifers during the performance experiment. Heifers with low RFI had greater MEm, but similar efficiencies of ME use for maintenance and gain as did high RFI heifers. Conclusion. These data indicated that selection based on RFI may not lead to improved energy efficiency in growing heifers. Implications. The results of this study indicated that low-RFI cattle may not have lower maintenance-energy requirements or differences in efficiencies of ME use than do high-RFI cattle. [ABSTRACT FROM AUTHOR]

Background: Provision of feed is a major determinant of overall profitability in beef production systems, accounting for up to 75% of the variable costs. Thus, improving cattle feed efficiency, by way of determining the underlying genomic control and subsequently selecting for feed efficient cattle, provides a method through which feed input costs may be reduced. The objective of this study was to undertake gene co-expression network analysis using RNA-Sequence data generated from Longissimus dorsi and liver tissue samples collected from steers of two contrasting breeds (Charolais and Holstein-Friesian) divergent for residual feed intake (RFI), across two consecutive distinct dietary phases (zero-grazed grass and high-concentrate). Categories including differentially expressed genes (DEGs) based on the contrasts of RFI phenotype, breed and dietary source, as well as key transcription factors and proteins secreted in plasma were utilised as nodes of the gene co-expression network. Results: Of the 2,929 DEGs within the network analysis, 1,604 were reported to have statistically significant correlations (≥ 0.80), resulting in a total of 43,876 significant connections between genes. Pathway analysis of clusters of co-expressed genes revealed enrichment of processes related to lipid metabolism (fatty acid biosynthesis, fatty acid β-oxidation, cholesterol biosynthesis), immune function, (complement cascade, coagulation system, acute phase response signalling), and energy production (oxidative phosphorylation, mitochondrial L-carnitine shuttle pathway) based on genes related to RFI, breed and dietary source contrasts. Conclusions: Although similar biological processes were evident across the three factors examined, no one gene node was evident across RFI, breed and diet contrasts in both liver and muscle tissues. However within the liver tissue, the IRX4, NR1H3, HOXA13 and ZNF648 gene nodes, which all encode transcription factors displayed significant connections across the RFI, diet and breed comparisons, indicating a role for these transcription factors towards the RFI phenotype irrespective of diet and breed. Moreover, the NR1H3 gene encodes a protein secreted into plasma from the hepatocytes of the liver, highlighting the potential for this gene to be explored as a robust biomarker for the RFI trait in beef cattle. [ABSTRACT FROM AUTHOR]

An investigation was carried out to explore the effect of dietary protein on growth, feed utilization efficiency, condition factor, and lengthweight relationships in common carp (Cyprinus Carpio). 3600 C. carpio were sourced from a Mosul fish hatchery and transported to a private farm in Khanki township, where they were divided into four groups of 900 each. Following a day of acclimation, the fish were placed in 4× 4× 3m water culture ponds and fed diets with different protein concentrations (T1: 30%, T2: 28%, T3: 30%, and T4: 35%) for 90 days. From each group, twenty fish were selected for data collection. Results indicated that the growth parameters, such as daily weight gain, total weight gain, weight gain rate, relative growth rate, metabolic growth rate, and specific growth rate, were higher in fish fed a 28% protein diet (T1) compared to other protein concentrations (T1: 30%, T3: 26%, and T4: 35%). Nutrient utilization parameters, including daily feed consumption, total feed consumption, daily protein consumption, and total protein consumption, were elevated in fish fed with 35% protein (T3). T2 exhibited a significantly higher feed efficiency ratio and protein productive value compared to other diets. The feed conversion ratio was markedly decreased in fish fed a 28% protein diet (T2). Fulton condition factor and modified condition factor were significantly elevated (P< 0.05) with a 28% protein diet (T2), while the relative condition factor decreased. The length-weight relationships indicated isometric growth in T3 (26, 35%), allometric positive growth in T2 (28%), and negative growth in T1 (30%). In conclusion, the study highlighted the superior growth performance and nutrient utilization efficiency in common carp when fed a 28% protein diet (T2). [ABSTRACT FROM AUTHOR]

Objective: To review the effects of feed restriction in finishing pigs on production efficiency and meat quality. Design/methodology/approach: A bibliographic review of feeding management in pigs fed ad libitum, restricted, and their combination was carried out. Results: Feed restriction decreases the growth rate, but if the restriction is moderate, better feed efficiency can be obtained. Feed restriction followed by feed ad libitum results in compensatory growth, which equals or improves continuous free access feeding. Study limitations/implications: Implementing feed restriction can be useful to improve feed efficiency and in periods that it is necessary to slow down growth. Findings/conclusions: Moderate feed restriction (-10%) of finishing pigs improves feed efficiency. Feed restriction of less than 20% for 30 days, followed by ad libitum feed, promotes compensatory growth and improves feed efficiency. [ABSTRACT FROM AUTHOR]

In Brazil, grazing is the main or only source of food for livestock. The appropriate combination of supplementation with concentrate in a lamb's diet on pasture is an alternative that can be explored to use natural resources to produce quality meat. The aim of the current study was to evaluate the effects of different supplementation levels (0%, 1.5%, and 3% of BW) on the intake, performance, and production costs of lambs grazing on Aruana (Megathyrsus maximus) and Marandu (Brachiaria brizantha) grasses. Thirty-six non-castrated male Suffolk lambs (22.54 ± 2.72 kg) were used. The lambs were evaluated for nutrient intake and digestibility, such as dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and consumption in relation to body weight (% BW), in addition to the average daily gain (ADG), body condition score (BCS), and hot carcass weight (HCW), as well as the rising production cost of each system. The dry matter of the green leaf blades was influenced by the pasture type (p < 0.05), producing 1503.6 vs. 2977.4 kg/ha of Aruana and Marandu grasses, respectively. The concentrate supplementation level influenced the type of pasture (p < 0.05). A higher consumption of DM, CP, NDF, and organic matter was registered for the supplemented animals (p < 0.05) and on Aruana grass. The intake in relation to body weight was significantly influenced by the concentrate levels (p < 0.05). The empty body weight and HCW were significantly influenced by the supplementation levels (p < 0.05). The ADG and feed conversion (FC; kg DM/ADG) were influenced by the supplementation levels and type of pasture. The BCSs differed between the concentrate levels (p < 0.05). The supplementation improved dry matter digestibility. The ADG and FC were superior in the supplemented animals, with an advantage for those grazing on Aruana grass. The slaughter ADG was also higher in the supplemented animals. The lambs' pasture comprising Aruana grass with 1.5% BW of concentrate supplementation showed improved production and economic results. [ABSTRACT FROM AUTHOR]

The use of high-grain diets in feedlots is associated with the development of acidosis and ruminitis, which can lead to the occurrence of liver abscesses (LAs). However, the effect of LA on carcass traits is not well known. This study assessed the effects of LA on the performance and carcass traits of beef cattle. Nine peer-reviewed publications with forty-seven treatment means were included in the data set. The effects of the LA were evaluated by examining the weighted mean difference (WMD) between LA (animal with LA) and control treatment (animal without LA). Heterogeneity was explored by meta-regression, followed by a subgroup analysis of the scores and percentages of liver abscess and concentrate level in the feedlot diet. Animals affected by LA showed a reduction in dry matter intake (−1.03%) and feed efficiency (−1.82%). Animals with an LA score of "A" (one or two small abscesses) exhibited a decrease in carcass weight (WMD = 3.41 kg; p = 0.034) and ribeye area (WMD = −1.37 cm2; p = 0.019). When assessing the impact of LA on carcass traits, the most reliable finding indicates a 1.21% reduction in the ribeye area, with no adverse effects observed on subcutaneous fat thickness or the marbling score in the carcass. [ABSTRACT FROM AUTHOR]

The catabolic activity of the ruminal microbial community of cattle enables the conversion of low-quality feedstuffs into meat and milk. The rate at which this conversion occurs is termed feed efficiency, which is of crucial importance given that feed expenses account for up to 70% of the cost of animal production. The present study assessed the relationship between cattle feed efficiency and the composition of their ruminal microbial communities during the feedlot finishing period. Angus steers (n = 65) were fed a feedlot finishing diet for 82 days and their growth performance metrics were evaluated. These included the dry matter intake (DMI), average daily gain (ADG), and residual feed intake (RFI). Steers were rank-ordered based upon their RFI, and the five lowest RFI (most efficient) and five highest RFI (least efficient) steers were selected for evaluations. Ruminal fluid samples were collected on days 0 and 82 of the finishing period. Volatile fatty acids (VFA) were quantified, and microbial DNA was extracted and the 16S rRNA gene was sequenced. The results showed that the ADG was not different (p = 0.82) between efficiency groups during the 82-day feedlot period; however, the efficient steers had lower (p = 0.03) DMI and RFI (p = 0.003). Less-efficient (high RFI) steers developed higher (p = 0.01) ruminal Methanobrevibacter relative abundances (p = 0.01) and tended (p = 0.09) to have more Methanosphaera. In high-efficiency steers (low RFI), the relative abundances of Ruminococcaceae increased (p = 0.04) over the 82-day period. The molar proportions of VFA were not different between the two efficiency groups, but some changes in the concentration of specific VFA were observed over time. The results indicated that the ruminal microbial populations of the less-efficient steers contained a greater relative abundance of methanogens compared to the high-efficiency steers during the feedlot phase, likely resulting in more energetic waste in the form or methane and less dietary energy being harvested by the less-efficient animals. [ABSTRACT FROM AUTHOR]

Simple Summary: As the dairy industry strives to improve the sustainability and efficiency of heifer rearing, it is important to understand the potential long-term impacts of early life events, such as social isolation stress, on the efficiency and performance of growing heifers. Pre-weaning pair housing has many immediate cognitive, growth, and feed intake benefits; however, little is known about the duration of these advantages over individually housed heifers. Pre-weaning isolation stress may have lasting adverse effects on heifer growth and feed efficiency, potentially inflating heifer rearing costs and decreasing farm profitability. To investigate possible long-term effects of pre-weaning housing, we measured the growth, feed efficiency, and methane emissions of 18-month-old heifers which had previously been paired or housed individually pre-weaning. Overall, pair-housed heifers maintained their initial body weight advantage over individually housed heifers with no adverse impacts on feed efficiency or methane emissions. Our objective in this exploratory study was to evaluate the long-term impacts of pre-weaning social isolation vs. contact on subsequent growth and feed efficiency of Holstein heifers. As pre-weaned calves, 41 heifers were housed individually (n = 15 heifers) or in pairs (n = 13 pairs; 26 heifers). At 18 months of age, heifers were blocked by body weight and randomly assigned to one of three pens within a block (six to eight heifers per pen; six pens total), with original pairs maintained. Body weight (BW), hip height and width, and chest girth were measured at the start and end of the study. Each pen was given 3 days of access to a GreenFeed greenhouse gas emissions monitor to assess potential physiological differences between treatments in enteric methane emissions or behavioral differences in propensity to approach a novel object. During the 9-week study, heifers were fed a common diet containing 62.3% male-sterile corn silage, 36.0% haylage, 0.7% urea, and 1.0% mineral (DM basis). To calculate daily feed intake, as-fed weights and refusals were recorded for individual heifers using Calan gates. Feed samples were collected daily, composited by week, and dried to calculate dry matter intake (DMI). Feed refusal and fecal samples were collected on 3 consecutive days at 3 timepoints, composited by heifer, dried, and analyzed to calculate neutral detergent fiber (NDF), organic matter (OM), and DM digestibility. Feed efficiency was calculated as feed conversion efficiency (FCE; DMI/average daily gain [ADG]) and residual feed intake (RFI; observed DMI-predicted DMI). Paired and individually housed heifers did not differ in DMI, ADG, FCE, or RFI. Although no differences were found in initial or final hip height, hip width, or chest girth, heifers which had been pair-housed maintained a greater BW than individually housed heifers during the trial. Methane production, intensity, and yield were similar between treatments. Pre-weaning paired or individual housing did not impact the number of visits or latency to approach the GreenFeed; approximately 50% of heifers in each treatment visited the GreenFeed within 8 h of exposure. Digestibility of OM, DM, and NDF were also similar between housing treatments. In conclusion, pre-weaning pair housing had no adverse effects on growth, feed efficiency, or methane emissions at 18 to 20 months of age. [ABSTRACT FROM AUTHOR]

Feed costs and carcass yields affect the profitability and sustainability of sheep production. Therefore, it is crucial to select animals with a higher feed efficiency and high‐quality meat production. This study focuses on the impact of dietary and genetic factors on production traits such as feed efficiency, carcass quality, and meat quality. Diets promote optimal sheep growth and development and provide sufficient protein can lead to higher‐quality meat. However, establishing an optimized production system requires careful consideration and balance of dietary parameters. This includes ensuring adequate protein intake and feeding diets with higher intestinal absorption rates to enhance nutrient absorption in the gut. The study identifies specific genes, such as Callipyge, Calpastatin, and Myostatin, and the presence of causal mutations in these genes, as factors influencing animal growth rates, feed efficiency, and meat fatty acid profiles. Additionally, variants of other reported genes, including PIGY, UCP1, MEF2B, TNNC2, FABP4, SCD, FASN, ADCY8, ME1, CA1, GLIS1, IL1RAPL1, SOX5, SOX6, and IGF1, show potential as markers for sheep selection. A meta‐analysis of reported heritability estimates reveals that residual feed intake (0.27 ± 0.07), hot carcass weight (0.26 ± 0.05), dressing percentage (0.23 ± 0.05), and intramuscular fat content (0.45 ± 0.04) are moderately to highly heritable traits. This suggests that these traits are less influenced by environmental factors and could be improved through genetic selection. Additionally, positive genetic correlations exist between body weight and hot carcass weight (0.91 ± 0.06), dressing percentage (0.35 ± 0.15), and shear force (0.27 ± 0.24), indicating that selecting for higher body weight could lead to favorable changes in carcass quality, and meat quality. [ABSTRACT FROM AUTHOR]

Advanced and innovative breeding and management of meat-producing animals are needed to address the global food security and sustainability challenges. Beef production is an important industry for securing animal protein resources in the world and meat quality significantly contributes to the economic values and human needs. Improvement of cattle feed efficiency has become an urgent task as it can lower the environmental burden of methane gas emissions and the reduce the consumption of human edible cereal grains. Cattle depend on their symbiotic microbiome and its activity in the rumen and gut to maintain growth and health. Recent developments in high-throughput omics analysis (metagenome, metatranscriptome, metabolome, metaproteome and so on) have made it possible to comprehensively analyze microbiome, hosts and their interactions and to define their roles in affecting cattle biology. In this review, we focus on the relationships among gut microbiome and beef meat quality, feed efficiency, methane emission as well as host genetics in beef cattle, aiming to determine the current knowledge gaps for the development of the strategies to improve the sustainability of beef production. [ABSTRACT FROM AUTHOR]

Ruminal ciliates are a fundamental constituent within the rumen microbiome of ruminant animals. The complex interactions between ruminal ciliates and other microbial guilds within the rumen ecosystems are of paramount importance for facilitating the digestion and fermentation processes of ingested feed components. This review underscores the significance of ruminal ciliates by exploring their impact on key factors, such as methane production, nitrogen utilization efficiency, feed efficiency, and other animal performance measurements. Various methods are employed in the study of ruminal ciliates including culture techniques and molecular approaches. This review highlights the pressing need for further investigations to discern the distinct roles of various ciliate species, particularly relating to methane mitigation and the enhancement of nitrogen utilization efficiency. The promotion of establishing robust reference databases tailored specifically to ruminal ciliates is encouraged, alongside the utilization of genomics and transcriptomics that can highlight their functional contributions to the rumen microbiome. Collectively, the progressive advancement in knowledge concerning ruminal ciliates and their inherent biological significance will be helpful in the pursuit of optimizing rumen functionality and refining animal production outcomes. [ABSTRACT FROM AUTHOR]