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The measurement and prediction of pasture intake in extensive grazing systems, typical of northern Australia, remain elusive after 50 years of research. The aim of this paper is to review research conducted over the past 50 years, highlight advances in understanding, discuss remaining challenges and consider future developments with digital technologies. While the fundamental components of voluntary intake are well understood, their measurement is difficult, particularly in extensive grazing systems, which has limited the development of predictive models that adequately address the interplay of factors influencing intake from the bite to the landscape scale. Ongoing research by the authors is used as an example to highlight the potential application of digital technologies to overcome limitations in measurement and prediction. Digital technologies offer the opportunity for monitoring factors that control voluntary pasture intake at scale and under commercial conditions. However, our ability to ground-truth novel indices of intake remains limited without ongoing development of physical methods. This will limit the accuracy and precision of predictive models incorporating digital technologies that can be applied to the extensive grazing conditions of northern Australia. The advent of precision livestock management for extensive cattle production is essential if the industry is to remain viable in the future where production is transparent, ethically sound and environmentally defensible as well as profitable. Feed intake is fundamental to animal performance and efficiency. Yet, for the cattle industry of northern Australia, our understanding of pasture intake is limited. While much is known about the components of feed intake, it remains difficult to integrate this knowledge into a dynamic and responsive estimation of voluntary intake under typical grazing conditions. This paper reviews the state of understanding, highlights gaps in knowledge and discusses the potential impact of digital technologies that will offer new solutions to old challenges. [ABSTRACT FROM AUTHOR]

Data concerning the practices and policies of collaborating properties for nutritional, breeding and health management of herds were captured by survey of herd owners/managers (n = 78) at the commencement of a large observational study conducted across northern Australia to identify and quantify the effect of major animal-, management group- and property-level risk factors on measures of reproductive performance. The cooperating herds in this study were considered to be broadly representative of north Australian beef breeding enterprises in terms of geography, size and ownership. Using four broad regional categories, this paper presents descriptive summaries of the management practices and nutritional conditions of cooperating herds in what was known as the Cash Cow project. Property sizes were largest within the Northern Downs and Northern Forest, and smallest within the Southern Forest. The expected average annual growth of yearling steers was >50 kg less in the Northern Forest, compared with the other country types, which also appeared to be associated with the identified production system and turnoff animal. Despite the exacerbated nutrition and environmental challenges and likely increased time required for new managers within the Northern Forest to attain an in depth understanding of the cattle and property dynamics, this region had the greatest incidence of management changes. The nutritional information summarised in this study highlights that available phosphorus during the wet season, as indicated by faecal levels in proportion to dietary energy, was likely to limit animal production within the Northern Downs and Northern Forest. During the dry season, pasture digestibilty and protein levels were likely to be approaching maintenance for cows on ~50% of properties in each country type and that responses to rumen degradable protein were also likely on 50% of properties. Despite this finding, low use of dry season supplements was observed for the Northern Downs, which was partially explained by the high incidence of the management systems based on segregating cows on lactation status and pregnancy. In all country types, the ratio of bulls to cows was higher than the 2.5% recommended for extensively managed situations, while limited use of vaccines to control infectious causes of reproductive loss was also observed. The major conclusion of this study is that there was marked variation in the adaption of interventions to specific businesses, indicating considerable opportunity exists for further adaptation in the region. A large epidemiological study known as the Cash Cow project was conducted in commercial beef breeding herds across northern Australia between 2007 and 2011 with the aim of determining and quantifying the effect of management, nutritional and environmental factors on reproductive outcomes. This paper describes results from survey questionnaires examining their nutritional, breeding and herd health management practices and policies completed by herd managers/owners of participating properties at the commencement of the study. [ABSTRACT FROM AUTHOR]

Context: There are multiple reports of high annual cow mortality rates in northern Australia, but no reports clearly indicating the overall rates and the impact of primary risk factors. Aims: The research aimed to determine which measured region-, property-, management group- and animal-level risk factors are associated with missing pregnant females. Methods: Risk factors for the annual rate of pregnant-cow mortality were investigated in an epidemiological study using outcomes for 21 554 cows from 52 beef herds in 2009 and 2010 in four primary country types within the mostly-dry tropical north Australian environment. Modelling of 2001–2011 Australian beef-herd statistics was used to corroborate and further quantify findings. Key results: In the epidemiological study, the overall predicted annual mean incidence of missing pregnant cows, a surrogate for mortality, was 10.9%, including lost tags and unrecorded cow movement that were estimated to constitute up to 9% missing cows. Risk factors associated with higher pregnant-cow mortality were as follows: not having follow-up rainfall more than 30 days after the first wet-season storms (4 percentage point increase); <2 t/ha of available pasture biomass in the early dry season (2–6 percentage point increase); pasture dry-season biomass <2 t/ha interacting with less than moderate mid-dry-season body condition score (3–10 percentage point increase); and, calving between April and September (non-significant trend for a 1–2 percentage point increase). Feed-quality measures did not affect mortality rate. Population modelling of Australian beef herd statistics suggested an average annual cow mortality rate in the Northern Forest region of ~7% compared with 2% in more nutritionally endowed regions. Conclusions: The major risk factor for cow mortality is under-nutrition, related either to generally-low soil fertility, seasonally-dry conditions, or management that exposes animals to poor nutrition. Annual mortality of pregnant cows appears 6–9 percentage points higher in the low-fertility Northern Forest region than elsewhere. Implications: Beef cow mortality is a major business cost in northern Australia. The efficacy of targeted management to achieve high cow performance was demonstrated by losses in a third of studied businesses in the Northern Forest being kept to the same or lower levels as median loss in endowed regions. An epidemiological study was conducted in commercial beef-breeding herds in northern Australia to determine and quantify the major associations between measures of performance and risk factors for herd management, nutritional, environmental and individual cow attributes. This paper presents the findings from the study using 21 554 pregnant cows in 52 herds that determined the major risk factors associated with those that went missing. This was supported by an analysis to calculate mortality rates using contemporary statistical data for the Australian beef herd. [ABSTRACT FROM AUTHOR]

Context: Sound reproductive efficiency is a key determinant for the overall productivity of a beef breeding business. For beef breeding herds to obtain high levels of reproductive productivity, breeding females need to efficiently become pregnant while lactating. Aims: This study aimed to determine and quantify the major factors associated with lactating cows becoming pregnant within 4 months of calving (P4M) in commercial beef breeding herds of northern Australia. Methods: A prospective epidemiological study was conducted using 78 commercial northern Australian beef breeding herds and involved 78 000 cattle that were monitored for 3–4 years. A multivariable model-building process was employed to scrutinise the resulting dataset to identify what herd-management practices, and nutritional, environmental and individual cow factors were major determinants of lactating cows becoming pregnant within 4 months of calving (P4M) and to estimate their magnitudes of effect. Key results: Overall, 41.6% of cows per production year were successful for P4M. Country type was strongly associated with 65.4%, 57.5%, 61.8% and 16.4% P4M for the Southern Forest, Central Forest, Northern Downs, and Northern Forest respectively. Between-year variability ranged between 3.3 and 11.7 percentage points. Cows calving in December–January (61%) had a substantially higher occurrence of P4M than did cows calving between July and September (15%). The difference in P4M when comparing availability of wet-season pasture protein and phosphorus was 12.7 and 20.3 percentage points respectively. Modelling of the impact of group seroprevalence and management group prevalence of recent infection with several infectious diseases was estimated, with a large negative association between group bovine viral diarrhoea seroprevalence and P4M suggested. Conclusions: This study further demonstrated the substantial impact that environment, herd management practices, nutrition and disease factors can have on the reproductive performance of females. Implications: To optimise the performance of females (through increasing the occurrence of cows contributing calves in consecutive years) under commercial conditions in northern Australia, herd managers should focus on maximising the proportion of cows within a herd calving at the desired time of the year, ensuring that any nutritional deficiencies and herd health issues are managed, and that cows are managed such that they are of good body condition score at the time of calving. An observational study was conducted in commercial beef breeding herds in northern Australia to determine and quantify the major associations between herd management, and nutritional, environmental and individual cow factors and measures of reproductive performance. This paper presents the findings of the study designed to determine the major predictors of lactating cows becoming pregnant within 4 months of calving. [ABSTRACT FROM AUTHOR]

Context: Sound reproductive efficiency is a key determinant for the overall productivity and profitability of a beef breeding business. Failure of a cow to conceive results in either culling or the cost of carrying non-pregnant animals. Aims: This study aimed to determine and quantify the major factors associated with non-pregnancy in commercial beef breeding herds of northern Australia. Methods: A prospective population-based epidemiological study of the likelihood of non-pregnancy in cows after an annual mating in northern Australian beef breeding cows used data from 73 herds from four broad country types and 62 323 animal years; approximately 80 property-, management-group- and cow-level risk factors were considered. A multivariable model building process was employed to scrutinise the resulting dataset, so as to identify what herd management practices, nutritional, environmental, and individual cow factors were associated with non-pregnancy and estimate their magnitude of effect. Key results: Non-pregnancy was disproportionately high in the Northern Forest (32.1%), compared with the Northern Downs, Central Forest and Southern Forest where it was 17.1%, 16.0% and 13.2% respectively. Time of expected calving had the largest impact on occurrence of non-pregnancy. Parity also had a significant influence, with first-lactation cows typically having 5–12% higher non-pregnancy than did mature cows. Non-pregnancy decreased with an increasing body condition score at the branding/weaning muster for lactating cows. The difference in non-pregnancy when comparing availability of wet-season pasture phosphorus content and digestibility of pasture during the dry season was 13.2 and 10.2 percentage points respectively. Conclusions: This study demonstrated the substantial impact environment, herd management practices, nutrition and disease factors can have on the reproductive performance of females. Implications: To optimise the efficiency of females (through reducing the occurrence of non-pregnancy) under commercial conditions in northern Australia, production systems should support beef herds calving early in the production year, being in at least moderate body condition and having access to more digestible pastures that address the nutritional requirements for both protein and phosphorus. This indicates focus for management, especially in the Northern Forest where the likelihood of non-pregnancy was highest. A large epidemiological study of annual pregnancy rate was conducted in commercial beef cattle breeding herds in northern Australia. The effect on non-pregnancy of the major herd management, nutritional and environmental risk factors and individual cow factors was determined and quantified. This paper presents the findings of the study designed to determine the major predictors of cows not achieving pregnancy. [ABSTRACT FROM AUTHOR]

Context: The accuracy of estimated breeding values (EBVs) is an important metric in genetic evaluation systems in Australia. With reduced costs for DNA genotyping due to advances in molecular technology, more and more animals have been genotyped for EBVs. The rapid increase in genotyped animals has grown beyond the capacity of the current genomic best linear unbiased prediction (GBLUP) method. Aims: This study aimed to implement and evaluate a new single-nucleotide polymorphism (SNP)–BLUP model for the computation of prediction error variances (PEVs) to accommodate the increasing number of genotyped animals in beef and sheep single-step genetic evaluations in Australia. Methods: First, the equivalence of PEV estimates obtained from both GBLUP and SNP-BLUP models was demonstrated. Second, the computing resources required by each model were compared. Third, within the SNP-BLUP model, the PEVs obtained from subsets of SNP were evaluated against those from the complete dataset. Fourth, the new model was tested in the Australian Merino sheep and Angus beef cattle datasets. Key results: The PEVs of genotyped animals calculated from the SNP–BLUP model were equivalent to the PEVs derived from the GBLUP model. The SNP–BLUP model used much less time than did the GBLUP model when the number of genotyped animals was larger than the number of SNPs. Within the SNP–BLUP model, the running time could be further reduced using a subset of SNPs makers, with high correlations (>0.97) observed between the PEVs obtained from the complete dataset and subsets. However, it is important to exercise caution when selecting the size of the subsets in the SNP–BLUP model, as reducing the subset size may result in an increase in the bias of the PEVs. Conclusions: The new SNP-BLUP model for PEV calculation for genotyped animals outperforms the current GBLUP model. A new accuracy program has been developed for the Australian genetic evaluation system which uses much less memory and time to compute accuracies. Implications: The new model has been implemented in routine sheep and beef genetic evaluation systems in Australia. This development ensures that the calculation of accuracies is sustainable, with increasing numbers of animals with genotypes. The accuracy of estimated breeding values is routinely provided to breeders as part of genetic evaluations in Australia. A new method to approximate accuracies using genomic information has been developed and is presented in this paper. The new model has been implemented in Australia's routine sheep and beef genetic evaluation systems. This development ensures that the calculation of accuracies is sustainable with increasing numbers of animals with genotypes. [ABSTRACT FROM AUTHOR]

Context: A great body of evidence is available on the in vitro efficacy of white-rot fungi (WRF) to degrade lignin in fibre-rich biomass (e.g. wheat straw, wood chips and rice straw (RS)) and improve the biomass' nutritive value for ruminants. Aims: Determining the impact of incubation temperature of three WRF to improve the nutritional value of rice straw. Methods: Growth of Ceriporiopsis subvermispora , Lentinula edodes and Pleurotus eryngii on RS for 26 days at the following six temperature regimes: continuous at 24°C, 30°C, 35°C and 40°C, and 3 days at 35°C and 40°C, with subsequent days at 24°C. In a follow-up experiment, improvement in fermentability in buffered rumen fluid of RS treated by the three WRF at 24°C and 30°C for up to 8 weeks was investigated. Key results: All three fungi grew at temperatures up to 35°C, with no growth observed at 40°C, with C. subvermispora being more temperature sensitive. There were significant differences in cellulose, hemicellulose and lignin degradation of RS at 24°C and 30°C, with C. subvermispora degrading 69% and 90% of the hemicellulose and lignin respectively at 30°C, greater than at 24°C (55% and 80% respectively). For L. edodes , there were significant differences in cellulose degradation between 24°C and 30°C, with 12% more degradation at 30°C, but not for hemicellulose and lignin. In vitro gas production showed no significant differences between the two incubation temperatures for either of the two fungi. Pleurotus eryngii treatment did not show any improvement in terms of in vitro gas production. Conclusions: Treatment of RS with L. edodes and C. subvermispora , but not P. eryngii , is robust and temperature changes will not have a major impact on their efficacy as long as the temperature remains below 30°C. Implications: Temperature during the incubation of WRF with rice straw needs to be below 30°C for this biotechnology to be applied in practice. White-rot fungus technology can revolutionise the utilisation of rice straw, because it enhances its quality by breaking down rigid components and boosting nutritional value. Investigating the temperature tolerance of these fungi is crucial for the practical application process, ensuring their effectiveness in diverse enviromental conditions and promoting their use in livestock feed. Unlocking their potential can increase the utility of this abundant by-product, contributing to environmental sustainability and agricultural productivity. This article belongs to the Collection Sustainable Animal Agriculture for Developing Countries 2023. [ABSTRACT FROM AUTHOR]

Context. Transport of cattle can be stressful and may lead to increased body temperature. It is necessary to quantify the effect of transport on body temperature so that informed management decisions can be made. Aims. This study aimed to determine the effects of a 5.5 h, 430 km road transport journey on body temperature (TB) of feedlot steers. Methods. Body temperature was obtained at 30 min intervals. All cattle were weighed and randomly allocated to a truck pen prior to transport. Cattle were transported on a single B-double truck, with three upper-deck and three lower-deck compartments. At 0630 hours, cattle were walked from their pens (25 m), weighed and loaded onto the truck. Loading was completed by 1030 hours. Key results. During the weighing and loading process prior to transport, mean TB increased from 39.37 ± 0.11°C to 40.21 ± 0.11°C. Immediately following loading, mean TB increased. The TB of cattle on the upper deck was 40.96 ± 0.08°C and on the lower deck 40.89 ± 0.08°C (P = 0.6299). During the first 3 h of the journey, the TB of lower-deck cattle decreased by 1.14°C (P < 0.01), compared with a 0.83°C reduction in cattle on the upper deck. Over the duration of the journey, which took 1 h longer than expected, the mean TB of the cattle on the upper deck (40.47 ± 0.11°C) was greater (P < 0.0001) than that on the lower deck (40.04 ± 0.12°C). One hour after unloading at the abattoir, pooled TB was 40.26 ± 0.12°C. Minimum TB (38.87 ± 0.04°C) occurred at 10.5 h after unloading. Conclusions. The results from this study highlight that increases in TB were more associated with cattle handling and loading events, rather than transport, under these environmental conditions. Understanding the magnitude of this increase will help managers decide on pre- and post-transport management of cattle. Implications. Cattle handling and loading for transport may lead to an increase in TB, which can remain elevated for a number of hours. However, it is unclear what the impact of hotter climatic conditions would have on trailer microclimate and, as such, TB regulation during road transport. [ABSTRACT FROM AUTHOR]

Context. Improved knowledge of the quality of the diet ingested by grazing cattle requires measurement of the diets selected, including in native pasture rangeland. Aims. The goal of the present study was to develop empirical equations to predict the intake, digestibility and protein concentration of the diet selected from faecal crude protein concentration of cattle grazing heterogeneous native grasslands through seasonal cycles in the Pampa biome of southern South America. Methods. In Experiment 1, cattle held in metabolism pens were fed native pasture at 15 and 22.5 g DM/kg bodyweight, or ad libitum. In Experiment 2, cattle also housed in metabolism pens were offered mixtures of the native pasture and Italian ryegrass at a proportion of 0.33 and 0.66 of the mixture, or pure ryegrass. Organic-matter intake (OMI), faecal crude protein excretion (fCP), faecal crude protein concentration (fCPc), OM digestibility (OMD) and diet crude protein concentration (dCPc) were measured in Experiments 1 and 2 and relationships were developed between the diet attributes and faecal crude protein (CP). In the Experiment 3, steers grazed native grasslands (NatG), or native grasslands overseeded with Italian ryegrass (NatG + RyeG). Intake and digestibility equations generated in Experiments 1 and 2 were then evaluated in Experiment 3 to estimate diet attributes from faecal protein measures. Key results. Three non-linear models (exponential, hyperbolic and mixed, i.e. exponential + hyperbolic) were examined to evaluate the OMD. The mixed model had the highest R2 value (0.74) and the lowest relative prediction error. OMI and dCPc were both linearly related to fCP. The OMD, OMI and dCPc equations were able to detect differences among diets in Experiment 3. Conclusions. It was verified that the faecal CP can be used to estimate key nutritional characteristics in cattle grazing heterogeneous grasslands in the Pampa biome in South America. Implications. Relationships between faecal CP and key diet attributes can be used to support further research and models for nutritional assessment of the diet and productivity of grazing cattle in the rangeland system examined. [ABSTRACT FROM AUTHOR]

Context. The knowledge of the genetic variability of gestation length and its correlations with other traits is relevant for selection decisions in beef cattle. Aims. Genetic parameters and trends were estimated for gestation length (first (GL1), repeated measures range of 1--6 (GL)) and traits currently used as selection criteria (birth weight (BW), weight gain from birth to weaning (BWG), weight gain from weaning to yearling (WYG), scrotal circumference (SC), score of conformation (YC), score of precocity (YP), and score of muscling (YM)) in Brazilian Angus cattle. In addition, direct and correlated selection responses were predicted. Methods. A series of single- and two-trait Bayesian analyses were performed on beef cattle data from14 farms across different regions of Brazil, by using linear and threshold animal models. Key results. A moderate heritability was estimated for GL1 (0.356 ± 0.058); however, the estimate for GL was low (0.189 ± 0.028) as was that for repeatability (0.204 ± 0.027). Lower accuracies of breeding values were obtained for GL than for GL1, ranging from0.490 ± 0.161 to 0.687 ± 0.037. Direct heritability estimates for growth and body composition traits were low, except for SC and BWG (0.301 ± 0.060 and 0.241 ± 0.019 respectively). Genetic correlations of 0.558 ± 0.121 and 0.739 ± 0.131 were estimated between GL1 and BW, and between GL and BW respectively. The other traits studied were estimated to have weak or nearzero genetic correlations with gestation length traits. Positive and moderate genetic associations were estimated between BW and BWG, SC, and visual scores (ranging from 0.338 ± 0.095 to 0.458 ± 0.092), but a near-zero estimate was obtained with WYG (0.127 ± 0.150). Weight gains were more highly genetically correlated with visual scores than between themselves (BWG and WYG) and with SC. The SC was highly genetically correlated with visual scores (0.684 ± 0.054 to 0.714 ± 0.050). Genetic trends showed that all traits studied have been changing in a positive direction, being unfavourable for BW and GL. Higher genetic gains were expected from using direct selection than from using indirect selection for GL1. Conclusions. Rapid growth is genetically associated with superior conformation, precocity and musculature, as well as a large scrotal circumference in males. However, selection decisions that heavily focus on these traits are likely to lead to more calving difficulties in the longer term. Implications. Selection indices should incorporate traits that measure calving difficulty directly if relevant records are available. Currently, considering its practical implications in primiparous anoestrus, the first-gestation length could serve as a viable alternative for inclusion in selection indices. Due to the low repeatability of the gestation length, decisions to cull on the basis of only one or two records of GL are highly inaccurate. [ABSTRACT FROM AUTHOR]

Context. Wagyu Feeder Check is a genomic-based tool designed to provide genomic estimated breeding values (GEBV) for five feedlot growth and carcase traits. At present, Wagyu Feeder Check is based on a reference population of 8316 genotyped and phenotyped Australian fullblood (FB; N = 2120) Wagyu and Wagyu-crossed (XB; N = 6196) cattle, principally Wagyu × Angus F1 animals. Aims. We provide technical details behind the development of the Wagyu Feeder Check and validate the ability of its GEBV to predict differences in performance of Wagyu cattle in daily weight gain at feedlot, carcase weight, carcase eye muscle area, carcase marbling score and carcase rump fat at the P8 site. Methods. Data supplied from eight commercial supply chains across Australia was used to generate GEBV using mixed-model equations that incorporated a genomic relationship matrix build with 82 504 autosomal markers. The bias, dispersion, and accuracy of the GEBV were evaluated using a four-way cross-validation scheme where, in each turn, the phenotypes from a random 1549 (or 25%) XB cattle were set as missing. Key results. The genomic estimate of the Wagyu content in the FB and XB population averaged 99.12% and 59.55%, respectively, and with most of the non-Wagyu content associated with Angus. The estimates of heritability (± s.e.) were 0.497 ± 0.016, 0.474 ± 0.004, 0.347 ± 0.014, 0.429 ± 0.003 and 0.422 ± 0.003 for daily weight gain at feedlot, carcase weight, eye muscle area, marbling and rump fat, respectively. Averaged across the four XB validation populations, the accuracy of GEBV was 0.624, 0.634, 0.385, 0.620, and 0.526 for the same set of traits. Conclusions. Genomic predictions generated by Wagyu Feeder Check can predict differences in feedlot and carcase performance of Australian Wagyu cattle. Given the large content of Angus in the XB population, further research is required to determine the predictive ability of GEBV in Wagyu × Bos indicus and Wagyu × dairy animals. Implications. Commercial feedlot operators finishing animals with a strong Wagyu breed component will benefit from using Wagyu Feeder Check for decision making. [ABSTRACT FROM AUTHOR]

Context. The Western Australian (WA) Government has set ambitious emission reduction targets and is developing strategies to reduce emissions across the state economy, including agriculture. Aims. This study determined the product carbon footprint (CF) and total emissions of the WA beef industry, to establish a baseline for emission reduction planning. Methods. A cradle-togate attributional life-cycle assessment with a reconciled livestock inventory of herd numbers and turnoff, was used. Emission reduction strategies were examined and included herd management, enteric-methane mitigation, and removals via carbon sequestration in vegetation and soils. Key results. Modelled livestock numbers were found to be 36% higher than reported in the Australian Bureau of Statistics (ABS), resulting in an emission profile of 4.7 million tonnes (Mt) of carbon dioxide equivalent (CO2-e) (excluding land use (LU) and direct LU change (dLUC)). This profile was 26% higher than emissions reported in state inventories. LU and dLUC were estimated to be a greenhouse-gas removal of -2.6 Mt CO2-e, although with high uncertainty. The mean CF for WA was 15.3 kg CO2-e per kg liveweight (LW) (excluding LU and dLUC). State-wide removals from LU and dLUC were estimated to be -8.5 kg CO2-e/kg LW. The CF was 11.7, 19.2 and 18.2 kg CO2-e/kg LW for the Agricultural, Kimberley and Arid regions respectively. The implementation of herd-management strategies and anti-methanogenic supplements resulted in a maximum 25% reduction. Conclusions. Herd productivity and market specifications were key drivers of regional differences in CF. Opportunities exist to reduce the CF in northern herds through diverting cattle to Australian backgrounding and feedlot supply chains to reach slaughter weight at a younger age. Adoption of anti-methanogenic feed supplements were important; however, achieving major reductions in the next decade will rely on removals via carbon sequestration in soil and vegetation. Implications. Considering the magnitude of removals and elevated uncertainty in this result, further research and new datasets are needed to refine this analysis. New datasets are required to accurately report livestock numbers and track and reduce future GHG emissions from this higher baseline. Technical, cost and adoption barriers will need to be addressed by developing actionable pathways to achieve emission reduction in the mid-to long term. [ABSTRACT FROM AUTHOR]

Context and aims. DNA metabarcoding strategy was used to sequence the 16S rRNA region of ruminal fluid samples from Nellore cattle fed with concentrate-rich diets in response to modulatory effect of buffering additives calcarea seaweed (Lithothamnium calcareum) and sodium bicarbonate. Methods. Besides characterising the richness and diversity indices of rumen bacterial community, the impact of potentially acidogenic diets on rumen pH, blood parameters, and short-chain fatty acid profile (SCFA) was investigated for which four male Nellore cattle were used, distributed in a 4 × 4 Latin square (treatments × periods). Treatments comprised the same highly concentrated basal diet, and were as follows: T1, without additive (CON); T2, inclusion of 90 g of sodium bicarbonate (BIC); T3, inclusion of 90 g of L. calcareum (L90); and T4, inclusion of 45 g of L. calcareum (L45). Data were analysed in R, in which diversity and abundance at gender level were analysed using Friedman's test, withmeans being adjusted by False Discovery Rate (FDR) correction. The analyses of pH, biochemical parameters and SCFA were analysed using Scott-Knott test and means were evaluated with a significance level of 10% (P < 0.10). Key results. We identified 1474 operational taxonomic units (OTUs) belonging to 52 genera and 16 phyla of bacteria domain. The results showed that bacterial microbiota were dominated by Firmicutes (44.12%), Bacteroidetes (28.29%), and Proteobacteria (5.88%). Animals fed with L90 demonstrated greater abundance and ruminal diversity for the Prevotella genus (P < 0.07% and P < 0.09% respectively), whereas cattle supplemented with L45 demonstrated greater diversity of the Fibrobacter genus (P < 0.05). There were differences in molar proportion for acetic (P < 0.07%) and valeric (P < 0.03%) acids in the period before feeding. Higher blood lactate concentrations were observed in animals supplemented with L45 (P < 0.06%), while animals that received treatments L90 and BIC presented lower levels of blood lactate. This metabolite was lower in animals fed with 90 g of sodiumbicarbonate and L. calcareum daily. These treatments also reduced the concentration of acetic acid and increased that of valeric acid, and improved ruminal diversity. Conclusions and implications. Our results supported this choice to improve ruminal function, with a great prospective of better weight-gain performance in Nellore cattle. [ABSTRACT FROM AUTHOR]

Nutritional management in rangeland beef cattle systems prioritises optimal body condition scores at calving for improved fertility and reproductive success. However, this focus often overlooks short-term dietary deficiencies before calving, which can lead to adverse outcomes for neonatal calves. This review explores the effects of beef cow malnutrition during the periparturient period on colostrum production, lactation onset, and passive immunity transfer to calves. Additionally, it discusses the long-term impact of such malnutrition on the offspring. By understanding how nutritional interventions affect the transition from gestation to lactation, it becomes possible to enhance calf health and survival in arid tropical environments. Commonly occurring short-term dietary restrictions, particularly protein deficiencies, can disrupt the hormonal equilibrium, resulting in reduced colostrum volume and quality, hindering calf growth and increasing mortality risks. Furthermore, dietary restrictions during this period affect critical physiological processes such as mammary gland blood flow and fetal small-intestine development. The review explores how these constraints influence colostrum production and immunoglobulin absorption by neonatal calves. Additionally, it highlights the significance of addressing other common nutrient deficiencies such as phosphorus and water and investigates the potential benefits of supplementing microbial products to enhance rumen function and protect cows from inflammation. Ultimately, addressing malnutrition during pregnancy is essential to prevent negative impacts on offspring performance, including alterations in carcass composition and muscle marbling. Consequently, cattle producers who aim for superior muscle marbling in the carcass by using costly genetics should give priority to enhancing nutritional programs for late-pregnant cows. In conclusion, a comprehensive understanding of the effects of malnutrition during the periparturient period on colostrum production, passive immunity transfer, and overall calf health is crucial for developing effective nutritional interventions that improve colostrum production, passive immunity transfer, and overall calf health in rangeland beef cattle systems. Ensuring proper nutrition during the peripartum period is crucial for healthy calf growth and survival. According to this review article, short-term dietary protein restrictions can disrupt hormonal balance, reduce colostrum quality and volume, and increase the risk of calf mortality, regardless of the cow's body condition score. The review highlights the need for cattle producers to develop improved nutritional programs for late-pregnant cows, particularly those focused on high muscle marbling in the carcass. [ABSTRACT FROM AUTHOR]

Context. Among the by-products derived from oilseeds, palm kernel cake (PKC) contains high concentrations of protein, fat, and fibre, which allows some flexibility in the use of this ingredient in ruminant diets. Aim. This study examined the effects of including palm kernel cake (PKC) in high-grain diets for cull cows on production performance, carcass traits, and meat fatty acid profile. Methods. Thirty-six ½ Girolando cows at 83 ± 5 months of age, with an average liveweight of 384.88 kg ± 59.18, were confined in collective stalls for 90 days. The animals were distributed into the following four diet groups: 0% (control), 8%, 16%, or 24% inclusion of PKC in the diet dry matter (DM). Key results. On the basis of regression analysis, the highest slaughter weight and carcass weight were at PKC inclusion levels of 11.5% and 10.3% respectively. Backfat thickness was greatest (8.8 mm, P < 0.01) in the carcasses of cows fed the diet with 15.1% PKC (on the basis of regression analysis), whereas the total lipid content in the meat decreased linearly (P < 0.05) with PKC inclusion. The C10:0, C12:0, C14:0, C14:1, C16:0, C16:1, C17:1, C18:0, C18:2n6t, and C20:5n3 fatty acids in the longissimus thoracis muscle responded quadratically (P < 0.05) to the inclusion of PKC. The highest concentration of desirable fatty acids was obtained with the inclusion of 11% PKC in the diet (on the basis of regression analysis). There was a linear increase in C14:1, C20:2, and C22:2 fatty acids and Δ9 desaturase 14 and 16 activity indices in the muscle of cows fed PKC. Conclusion. We recommend the inclusion of 10% PKC in the diet of cull cows fed high-grain diets. Intramuscular fatty-acid proportions were appreciably different from those reported for young B. taurus steers and heifers finished on high-concentrate diets. Implications. Therefore, inclusion of PKC is an excellent alternative to reduce production costs, having the availability and quality of the product as a limiting factor, since PKC is an industrial by-product. [ABSTRACT FROM AUTHOR]

Context. Identification earlier in life of beef cattle with capacity for increased marbling, improved carcase yield and/or reduced subcutaneous fatness can facilitate more rapid genetic improvement and identification of cattle more appropriate forfeedlot or pasture finishing. Earlierin life, ultrasound predictions have potential for significant improvements in compliance with market specifications and overall efficiency of beef production systems. Aims. To assess the relationships just prior to slaughter and earlier in life between measurements of intramuscular fat, subcutaneous fat and eye-muscle (Longissimus thoracis et lumborum) cross-sectional area made using ultrasound, and carcase fatness, muscling and yield measurements following slaughter of Bos taurus steers that differed genetically in potential for subcutaneous fatness and marbling. Methods. Ultrasound measurements of intramuscularfat (IMF), rib fat (RFT), P8 rump fat (P8FAT), eye-muscle area (EMA) and retail beef yield (RBY) of cattle heterogeneous for marbling and fat distribution were made at six stages of growth from weaning to long-feedlotting. Carcase measurements of the same traits were made at five stages of growth from weaning through to long-feedlotting. Key results. IMF ultrasound scans 168 days post-weaning were more strongly correlated (r = 0.79) with marbling in the carcase following long-feedlotting than were IMF ultrasound scans at the end of backgrounding (r = 0.71, 326 days post-weaning), short-feedlotting (r = 0.69, 431 days) and during (r = 0.59, 521 days) and at the end of long-feedlotting (r = 0.53, 585 days). P8FAT was the trait with the highest and most consistent accuracy across all stages of life (r = 0.80) between ultrasound and carcase measurements of P8FAT. Conclusions. The results of the present study showed that ultrasound-scanned measures of carcase IMF, subcutaneous fat and EMA can be used to predict carcase characteristics with good accuracy earlier in life. Implications. The finding that prediction of marbling in the carcase of long-feedlot-fed cattle was stronger by using ultrasound measurement of IMF in younger post-weaned cattle than in older post-weaned cattle warrants further investigation for genetic improvement and management applications, including using newer scanning technologies. [ABSTRACT FROM AUTHOR]

Context: Energy supplementation with highly fermentable carbohydrates can be a strategy to maximise the efficiency of nitrogen use (ENU) from high-nutritional value forages. Aims: The study aimed to investigate the independent or associated effects of two diurnal feeding times (0900 or 1700 hours) with two sources of energy supplementation (corn or citrus pulp) in the growing of F1 Angus × Nellore young bulls on palisade grass pastures, and their implications on the forage chemical composition, nutrient intake and digestibility, ENU, microbial protein synthesis, animal performance, and gain per area. Methods: There were 36 bulls used as experimental animals, with initial bodyweight (BW) of 290 ± 5 kg, and 32 similar bulls were used in a put-and-take system to maintain sward characteristics. The experiment was conducted in a complete randomised design with four treatments and three replications (paddocks). The treatments consisted of energy supplementation at 0.3% BW with corn or citrus pulp fed at 0900 or 1700 hours for four periods of 28 days. For evaluation of ruminal and blood parameters, ENU, intake, and nutrient digestibility, eight ruminal cannulated 1/2 Aberdeen Angus × 1/2 Nellore young bulls were used, with 280 ± 7 kg of initial BW, distributed in a 4 × 4 double Latin square design, consisting of four periods and four treatments. Key results: Supplementation at 0.3% of BW with corn or citrus pulp at 0900 or 1700 hours can reach up to 1.06 kg/day of young bulls reared on palisade grass pastures fertilised with 180 kg nitrogen/ha/year and managed at 25 cm of height compared with corn-based supplements. There were no effects on microbial protein synthesis or its efficiency. Conclusions: Citrus pulp can be used as an alternative energy source to corn, because it has the same potential for animal performance, ENU and microbial protein synthesis in tropical pastures with a high proportion of soluble protein, and structural and non-fibrous carbohydrates with high dry matter digestibility. Implications: Supplementing grazing beef cattle at 0.3% BW with corn or citrus pulp in the morning or afternoon is an efficient nutritional strategy to improve animal performance. Different responses of energy supplementation to grazing beef cattle may occur due to the type of energy substrate and the supplementation time. Citrus pulp supplied in the afternoon can improve beef cattle performance. Citrus pulp can replace corn as an energy supplement and it is a non-human edible food. [ABSTRACT FROM AUTHOR]

Context: Leucaena leucocephala (leucaena) is a leguminous shrub used for beef grazing in low-rainfall regions (<600–700 mm). Newer cultivars have the potential to extend adoption of the species to higher rainfall (>600–700 mm), frost-free areas of Australia. Aim: We compared productivity, nutritional value and animal performance of two leucaena cultivars, new psyllid-resistant Redlands and the 2010-released Wondergraze, under continuous grazing management in a higher rainfall environment. Methods: Growing steers were allocated to replicated established stands of Wondergraze or Redlands with inter-row mixed grass–legume pasture from January to July 2021. Pasture and leucaena were characterised for biomass and nutritive characteristics. Botanical composition was measured. Liveweight gain, rumen fermentation, and leucaena mimosine breakdown products were measured in grazing steers. Key results: At the beginning of the study, leucaena edible biomass was similar for both cultivars (P > 0.05), but at subsequent samplings, biomass of Redlands was lower than of Wondergraze (P < 0.01). Biomass of both cultivars declined rapidly over the grazing period. Pasture biomass increased between February and July and was significantly higher in Wondergraze paddocks (P < 0.05). Animal performance was not significantly different between cultivar treatments, averaging 0.8 kg/day, but declined over time. Patterns of mimosine conversion to DHP isomers and their conjugation were similar for the two cultivars, suggesting that effectiveness of detoxification did not differ between them. Conclusion: The results demonstrate that leucaena can sustain high levels of animal performance when included in tropical grass pastures in a higher rainfall environment if present in a sufficient quantity (>2 t leucaena edible dry matter/ha established leucaena). Implications: Grazing leucaena–grass pastures is an effective means of increasing animal productivity in parts of subtropical Australia. However, managing grass and/or leucaena growth to match animal requirements can be challenging. Psyllid-resistant leucaena cv. Redlands can produce levels of animal performance equal to those of the more established Wondergraze, achieving liveweight gains of 0.8 kg/day. Differences between Redlands and Wondergraze were small or non-existent, regardless of the parameter being compared, except for mimosine breakdown. High grazing-animal performance relies on a sustained optimum balance between grass and leucaena in the pasture. [ABSTRACT FROM AUTHOR]

Context: Environmental conditions during hot weather decrease feed intake and cattle growth. Aims: This study conducted over three consecutive years, during the summer, evaluated access to shade as a strategy to mitigate heat stress of finishing cattle in Uruguay. Methods: Each year, 32 Bos taurus and/or Bos taurus crossbred steers (initially weighing 461 ± 28 kg) were blocked by initial liveweight and assigned to one of eight pens, where one of two treatments were applied, namely, no shade access or shade access (mean shaded area 4.5 m2/animal). Finishing diet was offered three times per day and cattle had ad libitum access to water. Twenty-four pens were considered in a randomised complete-block design. Average daily gain (ADG), dry matter intake (DMI) and feed efficiency were measured, and hot carcass weight was collected at slaughter. Ruminal pH and temperature were obtained using ruminal boluses. Feeding, drinking, rumination, inactive behaviours, respiration rate and painting score were observed. Key results: Mean days on feed were 70.6 ± 5.5. The average THI ranged from 70 to 72. Steers with access to shade had greater DMI (P = 0.003), ADG (P = 0.004), and feed:gain ratio (P = 0.05) than did not shaded steers. Ruminal pH was higher (P < 0.0001) in shaded than in not shaded animals. The slaughter weight of shaded steers was 10 kg greater (P = 0.02) than that of not shaded steers. A trend (P = 0.06) to higher hot carcass weight after dressing was obtained by shaded steers. The average respiration rate and panting score was consistently lower (P < 0.0001) for shaded than for not shaded steers, except in the early morning. Access to shade increased the time spent by animals feeding (P = 0.008) and ruminating (P = 0.001), decreasing inactive time (P < 0.0001). Conclusions: Shade could improve performance and welfare of feedlot cattle during summertime, even in regions with an average THI from 70 to 72. Implications: Access to shade allowed fattening cattle to dissipate heat stored during the day at night and to alleviate the effect of heat load during summer in subtropical region. Cattle in outdoor feedlots are candidates for heat stress. We evaluated the shade effect in steers during finishing under humid subtropical climate. Shade access increased feeding and ruminating time, daily dry-matter intake, average daily gain, feed:gain ratio and carcass weight, and decreased inactive time, respiration rate and panting. Shade improves steers performance, behaviour, and physiology in a region with an average THI from 70 to 72. [ABSTRACT FROM AUTHOR]

Context: Residual feed intake is a relevant trait for beef cattle, given the positive impact on reducing feeding costs and greenhouse gas emissions. The lack of large databases is a restriction when estimating accurate genetic parameters for dry matter intake (DMI) and residual feed intake (RFI), and combining different data sets could be an alternative to increase the amount of data and achieve better estimations. Aim: The main objective was to compare Uruguayan data (URY; 780 bulls) and Canadian data (CAN; 1597 bulls), and to assess the adequacy of pooling both data sets (ALL) for the estimation of genetic parameters for DMI and RFI. Methods: Feed intake and growth traits phenotypes in both data sets were measured following the same protocols established by the Beef Improvement Federation. Pedigree connections among data sets existed, but were weak. Performance data were analysed for each data set, and individual partial regression coefficients for each energy sink on DMI were obtained and compared. Univariate and multivariate variance components were estimated by the restricted maximum likelihood (REML) for DMI, RFI and their energy sinks traits (average daily gain, metabolic mid weight and back fat thickness). Key results: There were some differences in phenotypic performance among data (P < 0.01); however, no differences (P > 0.1) were observed for phenotypic values of RFI between sets. Heritability estimates for DMI were 0.42 (URY), 0.41 (CAN) and 0.45 for ALL data, whereas heritability estimates for RFI were 0.34 (URY), 0.20 (CAN) and 0.25 for ALL data. The results obtained indicate selection on reducing RFI could lead to a decrease in DMI, without compromising other performance traits, as genetic correlations between RFI, growth and liveweight were low or close to 0 (−0.12–0.07). Conclusions: As genetic parameters were similar between national data sets (URY, CAN), pooling data (ALL) provided more accurate parameter estimations, as they presented smaller standard deviations, especially in multivariate analysis. Implications: Parameters estimated here may be used in international or national genetic evaluation programs. Residual feed intake is a relevant trait for beef cattle, given the positive impact on reducing feeding costs and greenhouse gas emissions. The study of genetic parameters for this trait is required, with the aim to be included into breeding programs. As the availability of large databases for this trait is limited, we study the performance of two sources of data, evaluating if they are possible to be pooled to estimate more accurate genetic parameters. [ABSTRACT FROM AUTHOR]

Context. Improving feed efficiency in livestock production is of great importance to reduce feeding costs. Aims. To examine the relationship between ruminal microbiota and variation in feed efficiency in beef cattle fed concentrate-based diets. Methods. Residual feed intake of 389 fattening bulls, supplied with corn-based concentrate and forage ad libitum, was used to estimate animals' feed efficiency. Faeces and ruminal fluid samples, from 48 bulls chosen at random, were collected to estimate their forage intake and to determine their apparent digestibility, ruminal fermentation and microbiota. Those animals with extreme values of feed efficiency (high-efficiency (HE, n = 12) and low-efficiency (LE, n = 13)) were subjected to further comparisons. Alpha biodiversity was calculated on the basis of the normalised sequence data. Beta diversity was approached through performing a canonical correspondence analysis based on log-transformed sequence data. Genera differential abundance was tested with an ANOVA-like differential expression analysis and genera interactions were determined applying the sparse correlations for compositional data technique. Keyresults. No differences in dry matter intake were found between the two categories of feed efficiency (P = 0.699); however, HE animals had higher apparent digestibility of dry matter (P = 0.002), organic matter (P = 0.003) and crude protein (P = 0.043). The concentration of volatile fatty acids was unaffected by feed efficiency (P = 0.676) but butyrate proportion increased with time in LE animals (P = 0.047). Ruminal microbiota was different between HE and LE animals (P = 0.022); both a biodiversity and genera network connectance increased with time in LE bulls (P = 0.005 for Shannon index and P = 0.020 for Simpson index), which suggests that LE animals hosted a more robust ruminal microbiota. Certain genera usually related to high energy loss through methane production were found to establish more connections with other genera in LE animals' rumen than in HE ones. Microbiota function capability suggested that methane metabolism was decreased in HE finishing bulls. Conclusions. Rumenmicrobiota was associated with feed efficiency phenotypes in fattening bulls fed concentrate-based diets. Implications. The possible trade-off between feed efficiency and robustness of ruminal microbiota should be taken into account for the optimisation of cattle production, especially in systems with intrinsic characteristics that may constitute a disturbance to rumen microbial community. [ABSTRACT FROM AUTHOR]

Context: The semiarid rangelands of northern Australia have high climate variability and a history of suffering periodic severe droughts. To remain viable, livestock businesses in the rangelands need to build resilience to climatic and market variability by regularly producing a profit and increasing wealth. Aims: Our aim was to use the farm-management economics framework to conduct a contemporary assessment of the profitability and resilience of alternative livestock enterprises in the semiarid rangelands of northern Australia. Methods: Livestock options were examined for a constructed, hypothetical property representative of the central-western Queensland rangelands (16 200 ha; long-term carrying capacity 1071 adult equivalents). First, the profitability of beef cattle, wool sheep, meat sheep and meat goat enterprises was assessed in a steady-state analysis using herd or flock budgeting models. Second, farm-level, partial discounted cash-flow budgets were applied to consider the value of integrating or fully adopting over time several of the alternative enterprises from the starting base enterprise of either a self-replacing (1) beef cattle herd or (2) wool sheep flock. Key results: In the steady-state analysis of existing enterprises, meat sheep and rangeland meat goat enterprises produced the greatest rate of return on total capital (3.9 and 3.7% per annum respectively). The operating profit, of all self-replacing herds or flocks, was most sensitive to meat prices. Where full investment in a wild dog exclusion fence around the boundary of the property, and some refurbishment of existing infrastructure, was required to convert from beef to small ruminant production, the investment increased the riskiness and indebtedness of the overall enterprise. This was the case even when the long-term operating profit of the property could be substantially improved, e.g. by a change to rangeland meat goats (extra A$45 700 profit/annum). Conclusions: Existing small ruminant enterprises in the semiarid rangelands of Queensland are profitable and resilient alternatives, based on contemporary prices. However, when changing from the predominant beef cattle enterprise, and incurring significant capital costs to do so, financial risk is substantially increased, which has implications for property managers. Implications: The farm-management economics framework should be used by individual grazing businesses for their specific circumstances, to support decision-making. To remain viable, livestock businesses need to build resilience to climatic and market variability by regularly producing a profit. The farm-management economics framework was used to conduct a contemporary assessment of livestock enterprises in the semiarid rangelands of Queensland. Existing small ruminant enterprises were profitable and resilient alternatives, based on contemporary prices. However, when changing from the predominant beef cattle enterprise, and incurring significant capital costs to do so, financial risk was substantially increased, which has implications for property managers. [ABSTRACT FROM AUTHOR]

Context: The beef market faces an increasing demand for an environmentally friendly production system with high-quality final products. The use of strategies that improve system efficiency without detriment on quality are desired for both producers and consumer. Aims: This study aimed to evaluate the effects of residual feed intake (RFI) and dietary inclusion of crude glycerin on carcass and meat quality traits of feedlot-finished Nellore cattle. Methods: Nellore bulls selected for growth and classified as high (n = 14) and low (n = 14) RFI, with average liveweight of 328 kg and age of 552 days were used. Bulls received a high-concentrate diet for 96 days before slaughter and were randomly allocated to two experimental diets in a 2 × 2 factorial arrangement: RFI class (low or high) and dietary inclusion (CG) or not (WCG) of crude glycerin (20% on dry-matter basis). Data were analysed with the SAS MIXED procedure considering RFI class and diet as fixed effects and selection line as a random effect. Key results: There were no significant differences between RFI classes for dry-matter intake during finishing or production traits. Dry-matter intake tended to be reduced by 16% in CG bulls, without alterations in production. Dietary glycerin inclusion tended to increase the protein content in the Longissimus muscle and significantly reduced the fat content. In low-RFI bulls, shear force was higher in unaged beef, and shear force and myofibrillar fragmentation index tended to be higher in meat aged for 14 days. RFI class did not affect Longissimus muscle fatty acid profile, which was highly influenced by dietary glycerin inclusion. Bulls allocated to the CG treatment had a reduction in saturated fatty acids, an increase in odd-chain fatty acids, and a trend towards increased omega-3 fatty acids, which significantly increased the omega-3:omega-6 ratio. Conclusions: The use of Nellore bulls classified as low-RFI and crude glycerin inclusion in finishing diets of Nellore cattle do not compromise production, carcass traits or beef properties. Implications: This approach increases the efficiency and sustainability of the production process and improves the nutritional characteristics of beef for human consumption. The study provides a strategy to improve beef production, through the optimisation of processes involving feed efficiency, beef quality and their interface. Our findings indicated that using efficient Nellore bulls and providing them high-energy feeds during the finishing phase increases efficiency of production and improves beef nutritional traits. [ABSTRACT FROM AUTHOR]

Context. Genotype imputation is an effective method to increase the number of SNP markers available for an animal and thereby increase the overall power of genome-wide associations and accuracy of genomic predictions. It is also the key to achieve a common set of markers for all individuals when the original genotypes are obtained using multiple genotyping platforms. High accuracy of imputed genotypes is crucial to their utility. Aims. In this study, we propose a method for the construction of a common set of medium density markers for imputation, which relies on keeping as much information as possible. We also investigated the impact of changing marker coordinates on the basis of the new bovine genome assembly, ARS-UCD 1.2, on imputation accuracy. Methods. In total, 49 754 animals with 45 364 single nucleotide polymorphism markers were used in a 10-fold crossvalidation to compare four different imputation scenarios. The four scenarios were based on two alternative designs for the reference datasets. (1) A traditional reference panel that was created using the overlapping SNP from five medium density arrays and (2) a composite reference panel created by combining SNPs across the five arrays. Each of the reference datasets was used to test imputation accuracy when the SNPs were aligned on the basis of two genome assemblies (UMD 3.1 and ARS-UCD 1.2). Key results. Our results showed that a composite reference panel can achieve higher imputation accuracies than does a traditional overlap reference. Incorporating mapping information on the basis of the recent genome build slightly improved the imputation accuracies, especially for lower density chips. Conclusions. Markers with unreliable mapping information and animals with low connectedness to the imputation reference dataset benefited the most from the ARS-UCD 1.2 assembly and composite reference respectively. Implications. The presented method is straightforward and can be used to setup an optimal imputation for accurate inference of genotypes in Australian Angus cattle. [ABSTRACT FROM AUTHOR]

Context. Studies have shown that favourable genetic correlations exist between female and male fertility traits. However, investigations regarding these correlations in Australian tropical beef cattle are limited to either pedigree or single-breed analysis. Aim. The study aims to use genomic information to estimate genetic parameters of six female and seven male fertility traits measured during the first 2 years of life, in two tropical breeds. Methods. Single-, bivariate and multi-trait models were used to analyse fertility data from Brahman (BB; 996 cows and 1022 bulls); and Tropical Composite (TC; 1091 cows and 998 bulls) cattle genotyped with high-density singlenucleotide polymorphism chip assay. Key results. Heritability estimates in BB cows ranged from low (0.07 ± 0.04) for days to calving at the first calving opportunity (DC1, days) to high (0.57 ± 0.08) for age at first corpus luteum (AGECL, days). In BB bulls, estimates varied from low (0.09 ± 0.05) for sperm motility (score 1-5) to high (0.64 ± 0.06) for scrotal circumference (SC) measured at 24 months (SC24, cm). Similarly, heritability estimates in TC cows were low (0.04 ± 0.03) for DC1 and high (0.69 ± 0.02) for AGECL. In TC bulls, the heritability was low (0.09 ± 0.05) for sperm motility and high (0.69 ± 0.07) for SC24. Within-sex for both breeds, blood concentrations of insulin growth-factor 1 (IGF1) measured in cows at 18 months (IGF1c) were negatively correlated with female fertility phenotypes. In BB, across-sex, bulls' blood concentration of IGF1 measured at 6 months (IGF1b) was a good indicator trait for the following four female traits: AGECL, the first postpartum anoestrus interval, age at first calving and DC1. In TC, IGF1b and percentage normal sperm were good predictors of female fertility phenotypes. Conclusions. The heritability estimates and genomic correlations from the present study generally support and confirmed the earlier estimates from pedigree analyses. The findings suggest that selection for female fertility traits will benefit male fertility, and vice versa. Implications. Heritability estimates and genomic correlations suggest that we can select for fertility traits measured early in life, with benefits within and across sex. Using traits available through veterinary assessment of bull fertility as selection indicators will enhance bull and cow fertility, which can lead to better breeding rates in tropical herds. [ABSTRACT FROM AUTHOR]

Context: High-throughput transcriptome sequencing (RNA-Seq) has been widely applied in cattle studies. Public databases such as the National Center for Biotechnology Information (NCBI) contain large collections of gene expression data from various cattle tissues that can be used in gene expression analysis research Aims: This study was conducted to investigate patterns of transcriptome variation across tissues of cattle through large-scale identification of housekeeping genes (i.e. those crucial to maintaining basic cellular activity) and tissue-specific genes in cattle tissues. Methods: Using data available in the NCBI Sequence Read Archive database, we analysed 1377 transcriptome data sequences from 60 bovine tissue types, identified tissue-specific and housekeeping genes, and set up a web-based bovine gene expression analysis tool. Key results: We found 101 genes widely expressed in almost all tissue and screened out five housekeeping genes: RPL35A , eIF4A2 , GAPDH , IPO5 and PAK2. Focusing on 12 major organs, we found 861 genes specifically expressing in these tissues. Furthermore, 187 significantly differentially expressed genes were found among six types of muscle tissues. All expression data were made available at our new website http://cattleExp.org, which can be freely accessed for future gene expression analyses. Conclusions: The housekeeping genes and tissue-specific genes identified will provide more information for researchers studying gene expression in cattle. Implications: The web-based cattle gene expression analysis tool will make it easy for researchers to access large public datasets. Users can easily access all publicly available RNA data and upload their own RNA-Seq data. Transcriptome data sequences (1377 in total) were downloaded from the NCBI SRA public database to investigate patterns of transcriptome variation across tissues of cattle. In total, 101 genes were widely expressed in almost all tissue and 187 significantly differentially expressed genes were found among six types of muscle tissues. All expression data can be freely accessed for future gene expression analyses through our web-based cattle gene expression analysis tool. [ABSTRACT FROM AUTHOR]

Context: Nitrate salts can be utilised by the rumen bacteria as a nitrogen source. Nitrate salts can induce a methaemoglobinaemia in cattle if consumed in sufficient quantities. Methaemoglobinaemia is the principal factor that leads to the onset of clinical signs for nitrate toxicity in cattle. A methaemoglobin concentration ≥20% is considered unsafe for cattle. There are, however, limited studies on the longer-term effects of nitrate supplementation on methaemoglobin formation in Bos indicus steers consuming forage that is reflective of northern Australia's poor quality, native pasture in the dry season. Aims: We hypothesised that the Australian government's recommended daily dose of nitrate salts given to Bos indicus cattle would not cause a methaemoglobinaemia in the blood >20% throughout a 70 day treatment period. Methods: A 70 day study was conducted to determine the methaemoglobin, carboxyhaemoglobin, total haemoglobin, growth rate and forage intakes of cattle supplemented with a non-protein-nitrogen treatment containing nitrate (6.48 g NO3/kg dry matter intake (DMI) or no nitrate and consuming a chaffed Flinders grass hay (Iseilema spp.), a C4 species. The dose rate of nitrate was selected to match the Australian government guidelines. Ten 3-year-old fistulated Bos indicus steers (mean liveweight ± s.d., 400.7 ± 26.2 kg) were randomly allocated into two groups (n = 5). Blood samples were collected at 0, 2, 4 and 6 h after treatment with nitrate or no nitrate on days 10, 30, 50 and 70 to measure haemoglobin fractions in the blood. Key Results: Nitrate treatment caused the mean methaemoglobin (P < 0.001), peak methaemoglobin (P < 0.001) and carboxyhaemoglobin (P = 0.008) concentration to be greater in the blood of steers compared with steers given no nitrate. Nitrate treatment had no general effect on the total haemoglobin, DMI or bodyweight of steers. Conclusions: Bos indicus steers treated with 6.48 g NO3/kg DMI develop a methaemoglobinaemia that does not exceed 20% of total haemoglobin for 70 days. This data supports the Australian government's recommended feeding rate of nitrate to sedentary Bos indicus steers. Implications: The Australian government's method for feeding nitrate to cattle is safe under the conditions of this study. Within the conditions of the study, Bos indicus steers treated with nitrate develop a methaemoglobinaemia that does not exceed 20% of total haemoglobin for 70 days. Although the data in the current study supports the Australian government's recommended dose rate as safe for cattle the data represents Bos indicus steers in a sedentary state. Further research is required to validate the dose rate of nitrate for cattle in an active state. [ABSTRACT FROM AUTHOR]