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The objective of this study was to evaluate the influence of different amounts of rumen-undegradable protein (RUP) on intake, N balance, performance, mammary gland development, carcass traits, and hormonal status of Holstein heifers at different physiological stages (PS). Sixteen prepubertal (PRE) heifers (initial BW = 106 ± 7.6 kg; age = 4.3 ± 0.46 mo) and 16 pubertal (PUB) heifers (initial BW = 224 ± 7.9 kg; age = 12.6 ± 0.45 mo) were used in an experiment over a period of 84 d. Four diets with increasing RUP contents (38, 44, 51, and 57% of dietary crude protein) and heifers at 2 PS (PRE or PUB) were used in a 4 × 2 factorial arrangement of treatments in a completely randomized design. Throughout the experiment, 2 digestibility trials were performed over 5 consecutive days (starting at d 36 and 78) involving feed and ort sampling and spot collections of feces and urine. At d 0 and 83, body ultrasound images were obtained for real-time carcass trait evaluation. The mammary gland was ultrasonically scanned at d 0 and every 3 wk during the experiment. Blood samples were taken at d 0 and 84 to determine serum concentrations of progesterone, estrogen, insulin-like growth factor I (IGF-I), and insulin. No interaction between PS and the level of RUP was found for any trait. Apparent digestibility of dry matter, organic matter, and neutral detergent fiber corrected for ash and protein was not affected by RUP level but was lower for PRE compared with PUB heifers. Sorting against neutral detergent fiber corrected for ash and protein (tendency only) and for crude protein was greater for PUB than PRE heifers. Pubertal heifers had greater average daily gain (905 vs. 505 g/d) and N retention (25.9 vs. 12.5 g/d) than PRE heifers. In addition, average daily gain and N retention were greatest at 51% RUP of dietary protein. Mammary ultrasonography indicated no effects of RUP amounts on mammary gland composition, whereas PRE heifers had greater pixel values than PUB, indicating higher contents of fat rather than protein in the mammary glands of PRE heifers. Serum progesterone and IGF-I concentration was affected only by PS, and PRE heifers had greater values of progesterone and IGF-I concentrations than PUB heifers. Serum insulin concentration was unaffected by PS but tended to be higher at 51% of RUP. In conclusion, an RUP level of 51% increases body weight, average daily gain, feed efficiency, and N retention in heifers regardless of the PS. In addition, PRE heifers have a lower sorting ability and reduced intake, total-tract digestibility, and N retention. They also have higher amounts of fat in their mammary glands, even at moderate growth rates. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the expression of genes involved in energy metabolism and volatile fatty acids (VFA) and urea transport in rumen epithelium of bulls with different feed efficiency based on residual feed intake (RFI). Twenty-seven Nellore bulls (age = 22.5 ± 0.8 mo; initial body weight = 401 ± 42 kg) were classified as either Low, Medium, and High (n = 9 per group) RFI and finished in individual pens. During the finishing phase animals were fed the same diet formulated to meet the requirements of 1.3 kg daily gain with a target finish weight of 550 kg. At the end of the trial, bulls were slaughtered and ruminal fluid was collected for further VFA analyses. Samples of rumen epithelium from ventral sac were rapidly excised, rinsed with phosphate buffered saline solution (pH = 7.04) and immediately immerged in RNA later solution within 2 mL tubes. After 48 h, rumen epithelium samples were placed at −80 °C until total RNA isolation and qPCR analysis. Data were analyzed using SAS 9.4 with α = 0.05; trends were determined as 0.10 > P > 0.05. The concentrations of total VFA, acetate, propionate, butyrate, valerate, isobutyrate, isovalerate, and acetate: propionate ratio did not differ ( P > 0.05) among RFI groups. The mRNA abundance of UQCR10 ( P < 0.01) and NDUFB4 (trend; P = 0.07) were greatest for High RFI animals. However, the mRNA abundance of ATP5H , COX10 , and SDHF2 did not differ ( P > 0.05) among treatments. No differences ( P > 0.05) were observed for mRNA abundance of genes associated with ion pumping ( ATP1B1 , ATP1B2 , ATP1B3 ), protein turnover ( IGF1R , MKI67 , UBA1 ), heat production ( UCP2 ), butyrate metabolism ( BDH1 , BDH2 , HMGCL , HMGS1 ), and VFA ( CA7 , DRA , NHE2 , MCT1 , and PAT1 ) and urea transport ( AQP3 , AQP7 , AQP8 , AQP10 , and SLC14A1 ) in rumen epithelium of bulls classified as High, Medium, and Low RFI. These findings may indicate that more efficient animals (Low and Medium RFI) have lower energy expenditure in this tissue, which likely contribute for their better efficiency compared to the less efficient (High RFI) bulls. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of ruminal and abomasum protein supplementation in cattle consuming tropical forages on nutritional characteristics, fibrolytic enzymatic activity, in vitro degradation of insoluble fiber, and the ruminal microbial community profile. Two experiments were sequentially conducted and differed only in the forage quality that was offered: medium-quality forage (MQF, 78.4 g of crude protein, CP/kg of dry matter, DM) and high-quality forage (HQF, 98.6 g CP/kg DM). Four Nellore young bulls fitted with rumen and abomasum cannulas were utilized, and the following supplementation schemes were evaluated: control (only forage), daily supply of 230 g of additional CP (casein) into the rumen, daily supply of 230 g of additional CP into the abomasum, and supply of 115 g of additional CP into the rumen and 115 g of additional CP into the abomasum. Experiments were conducted using a 4 × 4 Latin square design where two sequential squares were used, one for MQF and other for HQF. The improvement in forage quality increased (P < 0.05) intake, fiber digestibility, and nitrogen retention. Supplementation, independently of site (rumen, abomasum or both), increased (P < 0.05) nitrogen balance in the rumen and in the animal’s body. Ruminal supplementation increased (P < 0.05) rumen ammonia nitrogen concentration and consequently in vitro degradation rate of neutral detergent fiber. Enzymatic activity was not affected (P > 0.05) by forage quality. However, in disagreement with data of degradation and digestibility, decreases in enzymatic activity were observed mainly for post-ruminal supplementation. The improvement of forage quality increased (P < 0.05) the richness and diversity associated with liquid fractions from ruminal fluid, although there was no effect on solid fractions. The improvement in forage quality and protein supplementation increases nitrogen accretion in the animal body. Well-defined associations cannot be established between production characteristics and enzymatic activities, and rumen microbial diversity in cattle fed tropical forages and receiving protein supplementation. [ABSTRACT FROM AUTHOR]

Feed intake control in ruminants is based on the integration of physical constraints and metabolic feedbacks. Physical constraints are related to the fill caused by the weight or volume of digesta in the reticulo-rumen. The amount of neutral detergent fiber (NDF) in the rumen (RNDF) may be used as an indicator of rumen fill. The objective of this study was to develop equations predicting RNDF from diet and animal characteristics using a meta-analysis technique. A treatment mean data set (n = 314) was obtained from 84 studies, in which rumen pool size and diet digestibility were determined in lactating cows (n = 231) or growing cattle (n = 83). The data were analyzed using linear and nonlinear mixed models. Intake, rumen pool size, and fecal output of NDF were scaled to body weight (BW)1.0. Due to the heterogeneous nature of dietary NDF, predictions of RNDF based on NDF intake were not precise. Predictions were markedly improved by dividing NDF into potentially digestible and indigestible fractions, because rumen turnover time of indigestible NDF was 2.7 times longer than that of potentially digestible NDF. At equal NDF intake, RNDF was negatively associated with dietary crude protein concentration and positively with the proportion of concentrate in the diet. Models based on fecal NDF output generally performed better than those based on NDF intake, probably because the effects of intrinsic characteristics of dietary cell walls and associative effects of dietary components collectively influence fecal NDF output. The model based on fecal NDF output was improved by including dietary concentration of forage NDF in the model, reflecting slower turnover of forage NDF compared with concentrate NDF. The curvilinear relationship between fecal NDF output and RNDF could be described by a quadratic, Mitscherlich, or power function equation, which performed better than the quadratic or Mitscherlich equation. In addition to fecal NDF output and dietary concentration of forage NDF, animal and forage type had significant effects on RNDF. At the same fecal NDF output, growing cattle had a smaller RNDF than dairy cattle. Increased proportion of alfalfa or corn silages in forage decreased RNDF and increased proportion of tropical forages decreased it. It is concluded that RNDF can be predicted precisely from intake or fecal output data, and that predicted RNDF can be a useful tool in understanding the interplay between physical and metabolic factors regulating feed intake in ruminants. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to evaluate ether extract (EE) concentrations, pigments, and wax in forages (n =14), concentrates (n =23), and cattle feces (n =100) using extraction methods recommended by Association of Official Analytical Chemists (AOAC; method 920.39) and American Oil Chemist''s Society (AOCS; method Am 5-04). The EE contents were compared by adjusting a linear regression model for each sample type. For the feces and forage samples, the EE contents produced by the AOCS method were greater (P<0.05) compared to those obtained using the AOAC method. No differences between methods were observed in EE content of concentrates (P>0.05). Concentration of vegetable pigments and wax were evaluated by using analysis for variance. Vegetable pigments were lower (P<0.05) in the post-extraction residues using the AOCS method, than the AOAC method, indicating greater participation of vegetable pigments in the EE. No differences were observed between the methods in wax concentration of the post-extraction residues (P>0.05). The quantification method of the EE content that is recommended by AOCS is not suggested for analyses of forage and feces of ruminants because it possibly increases the removal of non-fatty material, mostly pigments, in comparison to the method recommended by AOAC. [Copyright &y& Elsevier]

Abstract: Determination of the energetic contribution of different chemical components of cattle diets based on the content of total digestible nutrients (TDN) has been suggested by several authors and was adopted by the NRC [National Research Council (NRC), 2001. Nutrient Requirements of Dairy Cattle, seventh ed. Academic Press, Washington]. The main objective of that proposal is to overcome the high costs and the extended time of traditional in vivo digestion assays. Although theoretically based, the summative system adopted by the NRC [National Research Council (NRC), 2001. Nutrient Requirements of Dairy Cattle, seventh ed. Academic Press, Washington] has been shown to be inaccurate in predicting the TDN content of individual feeds or diets under tropical conditions. Therefore, a new model, that also uses a summative approach, was developed but it was based on data obtained in the tropics. The new model consists of equations that predict the digestible fractions of ether extract (n =108), crude protein (n =93), non-fibrous carbohydrates (n =84), and neutral detergent fibre (n =164). Non-fibrous components were evaluated by the Lucas [Lucas, H.L., 1960. Relations Between Apparent Digestibility and the Composition of Feed and Feces. 1: A Quantitative Theory. North Caroline State College, Raleigh] test to obtain true digestibility coefficients, and by the factorial system to distinguish between truly digested and metabolic fractions. Fibre components were evaluated using an adaptation of the surface law to obtain the indigestible fraction and a meta-analysis approach to obtain digestibility coefficients of the potentially digestible fraction. The estimates obtained with the new model were validated and compared to those produced with the model adopted by the NRC [National Research Council (NRC), 2001. Nutrient Requirements of Dairy Cattle, seventh ed. Academic Press, Washington] for cattle managed under tropical conditions. Data from four trials, two with lactating cows (n =63) and two with growing and finishing cattle (n =44) were used. The estimates produced with the two models were compared based on the decomposition of the mean square prediction error. It can be concluded that the new model was more accurate in predicting TDN values than the NRC [National Research Council (NRC), 2001. Nutrient Requirements of Dairy Cattle, seventh ed. Academic Press, Washington] model under tropical conditions. [Copyright &y& Elsevier]

The objective was to quantify the energy and protein nutritional requirements of Holstein × Gyr crossbred preweaned dairy calves until 64 d of age. Thirty-nine Holstein × Gyr crossbred male calves with an average initial live weight (mean ± SEM; for all next values) of 36 ± 1.0 kg were used. Five calves were slaughtered at 4 d of life to estimate the animals' initial body composition (reference group). The remaining 34 calves were distributed in a completely randomized design in a 3 × 2 factorial arrangement consisting of 3 levels of milk (2, 4, or 8 L/d) and 2 levels of starter feed (presence or absence in diet). At 15 and 45 d of life, 4 animals from each treatment were subjected to digestibility trials with total collection of feces (for 72 h) and urine (for 24 h). At 64 d of age, all animals were slaughtered, their gastro-intestinal tract was washed to determine the empty body weight (EBW; kg), and their body tissues were sampled for subsequent analyses. The net energy requirement for maintenance was estimated using an exponential regression between metabolizable energy intake and heat production (both in Mcal/EBW0.75 per d) and was 74.3 ± 5.7 kcal/EBW0.75 per d, and was not affected by inclusion of starter feed in the diet. The metabolizable energy requirement for maintenance was determined at the point of zero energy retention in the body and was 105.2 ± 5.8 kcal/EBW0.75 per d. The net energy for gain was estimated using the EBW and the empty body gain (EBG; kg/d) as 0.0882 ± 0.0028 × EBW0.75 × EBG0.9050±0.0706. The metabolizable energy efficiency for gain (kg) of the milk was 57.4 ± 3.45%, and the kg of the starter feed was 39.3 ± 2.09%. The metabolizable protein requirement for maintenance was 3.52 ± 0.34 g/BW0.75 per d. The net protein required for each kilogram gained was estimated as 119.1 ± 32.9 × EBW0.0663±0.059. The metabolizable protein efficiency for gain was 77 ± 8.5% and was not affected by inclusion of starter feed in the diet. In conclusion, the energy efficiency for gain of milk is higher than that of starter and the net protein required per unit protein gain increases with empty body weight. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the effect of supplying different levels of raw milk, alone or in combination, with access to a starter feed, on the intake, digestibility, daily gain, N balance, and body composition of Holstein x Gyr crossbred suckling calves until 64 d of age. Thirty-nine male calves aged 4 d with an average initial live weight of 36 ± 1.0 kg were used. Five calves were defined as a reference group and slaughtered at 4 d of age to estimate the initial body composition of the animals. The other calves were distributed according to a completely randomized design in a 3 x 2 factorial arrangement consisting of 3 levels of milk (2, 4, or 8 L/d) and 2 levels of starter feed (presence or absence in diet). At 15 and 45 d of age, 4 animals from each treatment were subjected to digestibility trials with total collection of feces and urine and sampling of feeds. At 64 d of age, all animals were slaughtered and their body tissues were sampled for analyses. Total dry matter and nutrient intake increased linearly and starter intake decreased linearly in response to the supply of increasing amounts of milk. The digestibility coefficient of organic matter was not affected by the inclusion of starter feed and increased linearly as milk supply was elevated. Daily gain was greater at increased milk supply levels and also greater when starter was supplied, without any interaction between milk supply level and the presence or absence of starter. Fecal N excretion and N retention were higher in the animals fed starter feed. Fecal N excretion was not affected by milk levels, whereas N retention was affected. Body protein and ash contents decreased linearly according to increased milk allowance. In contrast, fat body content increased linearly according to milk supply. The presence of starter feed in the diet was responsible for the increased body fat content, but had no effect on protein or ash content. In conclusion, weight gain and N retention in calves up to 64 d of age increased with milk supply. Ad libitum access to starter further increased weight gain and N retention and no interaction with milk allowance level occurred. However, greater levels of milk are also associated with reduced starter feed intake, in addition to increased body fat content. [ABSTRACT FROM AUTHOR]

We aimed to assess whether guanidinoacetic acid (GAA) affects the performance, metabolism, and placental vascularization of pregnant beef cows during late gestation as well as its impact on the offspring's performance. Twenty-eight pregnant Brahman cows, averaging 532±15.1 kg and carrying male (n=15) and female (n=13) fetuses, were used. The basal diet consisted of 688 g/kg corn silage, 147 g/kg sugarcane bagasse, 47.7 g/kg corn, 89.6 g/kg soybean meal, 6.86 g/kg urea, and 21.2 g/kg mineral mixture (DM basis). Cows were fed the experimental diets from 180 to 270 days of gestation. The following treatments were evaluated: control (no addition of GAA) or addition of 0.2 % GAA to the total diet (DM basis). There was no effect (P≥0.37) of GAA on voluntary intake. Similarly, GAA addition did not affect (P≥0.54) cows performance variables, except for ribeye area (REA), which had a lower (P<0.01) variation compared to the initial REA in cows fed dietary GAA compared to the control group. Dietary GAA increased (P≤0.02) both serum nitric oxide and placental vascularization compared to cows fed the control diet. There was no effect (P≥0.43) of GAA on urine and serum creatine concentrations. In contrast, dietary GAA increased (P≤0.03) plasma concentration of arginine, ornithine, citrulline, and tyrosine compared to the control. Conversely, dietary GAA decreased (P<0.02) plasma methionine concentration. Dietary GAA increased AGAT activity (P<0.03) in the liver, with no differences observed (P>0.68) on GAMT activity. There was no effect (P≥0.15) of GAA on performance of the offspring. Addition of GAA in maternal diet did not affect skeletal muscle fiber number (P>0.09) and diameter (P>0.23) of the offspring. Guanidinoacetic acid decreases skeletal muscle mobilization and enhances placental vascularization of beef cows during late gestation. However, providing GAA seems to not affect the performance of the offspring. • We aimed to evaluate the potential of guanidinoacetic acid (GAA) as a feed additive for beef cows during late gestation. • GAA demonstrates to have an effective arginine-sparing effect in beef cows during late gestation. • Dietary GAA addition enhances placental vascularization of beef cows during late gestation. • Providing GAA to beef cows at late gestation did not affect the performance of their offspring. [ABSTRACT FROM AUTHOR]

Abstract: The objective was to determine digestible fraction values of several tropical forages used in ruminant diets in the tropics through in vivo digestion in order to estimate the metabolizable energy (ME) content of these forages using several methods and predictive equations, and to assess the relationship between in situ neutral detergent fibre (NDF) degradability and in vivo NDF digestibility. In the experiment, 28 confined Nellore heifers 293±46.0kg live weight, were fed chopped sugar cane, sugar cane silage, soybean silage, mombaça silage (Pannicum maximum cv. Mombaça), corn silage, Tifton-85 hay (Cynodon spp.) and chopped elephant grass (Penissetum purpureum cv. Cameroun). Forages with crude protein (CP) below 70g/kg DM were supplemented with urea and ammonia sulphate (9:1). The feeding period lasted 12 days, consisting of 7 days for adaptation and 5 for total fecal collection. The ME estimated from was based upon chemical component fractions and the same system using digestible NDF (NDFd) after 48h of in vitro incubation (NRC48) was examined. The UC Davis (UCD) approaches based on several chemical components and an in vitro NDF digestion at 30 and 48h of incubation, respectively, UCD30 and UCD48, were evaluated. The other UCD approach (UCD Gas), which predicts ME from in vitro gas produced after 24h (24h Gas), 48h (48h Gas) and 72h (72h Gas) of incubation, was also examined. The equations developed under tropical conditions by Detmann also calculate digestible energy from the apparent digestible fractions of crude protein (CPad), ether extract (EEad), non-fibre carbohydrates (NFCad) and neutral detergent fibre (NDFad) (Detmann 1). The equations proposed in Detmann 1 were used again, but the estimator was changed to apparently digestible CP (CPad) (i.e., Detmann 2). The poor results associated with the descriptive levels of probability compared to the null hypotheses show the inadequacy of the UCD30, NRC48, 24h Gas and UCD gas models in predicting ME of these forages. The highest accuracy was with the NRC, Detmann 1 and Detmann 2 models as reflected in the lowest estimates of MSPE (6.297; 6.274; 6.236, respectively) and the lowest bias (0.458; 0.040; 0.162, respectively) among all models evaluated. For the CPad, a similarity was verified between the estimates with the submodel proposed by the , as well as by the Detmann 2 submodel and in vivo observations. The submodels proposed by the and Detmann diverged from the observed values of digested levels of EE. Similarities between observed and estimated values in the NDFd diet levels occurred. However, a higher predictive adequacy occurred in the Detmann 1 submodel. The same behavior occurred in estimates obtained for digestible fractions of NFC, suggesting that both models satisfactorily estimate the NFCad, with a higher prediction adequacy associated with the lowest bias in the Detmann 1 submodel. The systems based upon chemical composition, such as and Detmann allowed accurate estimates of ME but higher precision and accuracy occurred in the Detmann submodels for predicting the ME value of tropical feeds. [Copyright &y& Elsevier]

[Display omitted] • Nitrogen supplementation must be prioritized in systems with tropical forage. • Both nitrogen and starch supplementation are essential to improve ruminal fermentation. • Nitrogen and starch supplementation increase total volatile fatty acids production. • Nitrogen and starch supplementation do not improve CH 4 and CO 2 production rates. • The starch supplementation increases propionate and butyrate production. The aim was to evaluate the effects of supplementation with nitrogen and nitrogen plus starch in tropical grass hay (TGH) on neutral detergent fiber (NDF) and dry matter (DM) in vitro digestibility, pH, ammoniacal nitrogen (NH 3 -N), volatile fatty acids (VFA), methane (CH 4), and CO 2 emissions. The study was divided into two sets, first, evaluating the level of nitrogen to be supplemented: control (CON -TGH, 68 g CP/kg DM), low nitrogen (LN- TGH +90 g CP/kg DM), and high nitrogen (HN- TGH + 130 g CP/kg DM). The second set aimed to evaluate the level of nitrogen and starch to be supplemented: low nitrogen and low starch (LNLS - TGH + LN + 10% forage weight in starch supplementation-SS), high nitrogen and low starch (HNLS- TGH + HN + 10% SS), low nitrogen and high starch (LNHS - TGH + LN + 20% SS) and high nitrogen and high starch (HNHS - TGH + HN + 20% SS). Samples were incubated in serum bottles (50 mL) and each run was replicated 4 times. The measurements of NDF and DM digestibility, NH 3 -N concentration, and pH were performed at 3, 6, 9, 12, 24, 36, 48, 72, and 96 h, and CH 4 , CO 2 , and VFA were evaluated after 24 h. All data were analyzed using a completely randomized design in factorial scheme. Differences across treatments were investigated using five contrasts. In the first set, two contrasts were used to evaluate the nitrogen effect (linear and quadratic). In the second set, three contrasts were used to evaluate the effects of nitrogen, starch, and interaction between them. In the first set, there was linear nitrogen effect on NDF digestibility (p = 0.037), pH (p = 0.001), NH 3 -N (mg/dL; p = 0.001) and CO 2 (g/g digestible DM; p = 0.042). Quadratic nitrogen effect was observed on CO 2 production (mL, g/g DM and g/digestible DM; p < 0.050). In the second set, nitrogen supplementation improved undegradable NDF fraction, pH and NH 3 -H (mg/dL; p < 0.050) levels. The starch supplementation increased propionate, butyrate (mmol/d; p < 0.050), and CO 2 production (mL and g/g DM; p = 0.004). There was no nitrogen and nitrogen plus starch effect on CH 4 production. In conclusion, nitrogen supplementation increased NDF digestibility, NH 3 -N concentration, and pH. Moreover, the supplementation with nitrogen (130 g/kg DM) plus starch (20% of TGH) provided greater VFA production. However, despite the benefits of nitrogen or nitrogen plus starch supplementation on nutritional parameters, they were not effective to reduce CH 4 and CO 2 production. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of sex and levels of dietary crude protein (CP) on the recovery of 15 N in microbial protein as well as to evaluate nitrogen balance compounds and variables related to urea renal handling in Nellore cattle. Four Nellore bulls and four Nellore heifers, fitted with rumen cannulas, were distributed in a two 4 × 4 Latin square design. The four experimental diets differed in levels of CP: 90.0, 110.0, 130.0, and 150.0 g/kg on a dry matter basis. Continuous intravenous infusion of 15 N 15 N-urea solution was provided at a rate of 0.30 mmol urea/h followed by determination of 15 N in ruminal bacteria, ammonia (NH 3 ), and feces to determine the incorporation of recycled N in rumen bacteria. The increased dietary CP revealed a linear increase (P < 0.05) in total digestible nutrients (TDN), total digestibility of CP and neutral detergent fiber (NDF), retained nitrogen, urinary excretion of urea-N, amount of filtered and absorbed urea (g/day), and plasmatic concentrations of urea-N. Fecal excretion of N presented a linear increase (P < 0.05) in relation to dietary CP. Rumen NH 3 concentration increased in a linear fashion (P < 0.05), and rumen 15 N-NH 3 contents and fecal 15 N contents decreased in a linear fashion (P < 0.05) with increasing dietary CP. The regressions NH 3 = 23.6183 × e (0.0104×NI) and 15 N-NH 3 = −0.00062 × NI + 0.1219 were obtained in order to calculate rumen NH 3 concentrations (mg/l) and 15 N-NH 3 (atom percent excess), respectively, as a function of N intake (NI, g/day). The contents of total-N and 15 N did not differ between liquid-associated bacteria (LAB) and particle-associated bacteria (PAB). There was no effect of sex (P > 0.05) on the percentage of infused 15 N that was recovered from feces and bacteria. There was no effect of dietary CP level on the percentage of 15 N infused in plasma that was recovered from feces. However, there was a decreasing linear effect of the level of dietary CP (P < 0.05) on the percentage of 15 N infused in the jugular vein recovered from bacteria. We concluded that microbial protein synthesis was not affected by sex. The LAB and PAB had the same total-N content and recovery of infused 15 N-urea. The greater recovery of infused intravenous 15 N-urea on microbial protein synthesis in a low CP diet suggests greater urea recycling in association with this diet. [ABSTRACT FROM AUTHOR]

An experiment was conducted to evaluate whether a reduction in dietary crude protein (CP) content affects animal performance, energy and protein requirements, N losses, and enteric methane emission in finishing Nellore bulls. Twenty-six animals, with an average age of 20 ± 1.0 months and initial body weight (BW) of 296 ± 8.1 kg were used in this experiment. Four animals were used as baseline reference animals and were slaughtered at the beginning of the experiment. Four animals were fed at maintenance level (MAIN), whereas 18 bulls were divided into 3 groups ( n = 6 in each group) and were randomly assigned to the treatments consisting of three levels of CP in the diets: 10, 12, and 14% of CP. At the end of the experiment, all animals were slaughtered to evaluate their chemical body composition, energy and protein requirements, and carcass characteristics. A linear effect was observed for dietary CP level on CP intake and digestibility, while greater values were obtained for animals that were fed 14% CP. Nitrogen metabolism was affected by CP levels, where animals that were fed 12 and 14% CP had greater urinary N losses than those that were fed 10% CP. There was no effect of CP level on retained N, animal performance, and carcass characteristics among diets, and there was no effect of CP level on microbial efficiency and CH 4 emissions. Thus, this study showed that for finishing bulls, the level of dietary CP did not interfere with muscle deposition and greenhouse gas emissions. The reduction of CP content in diets does not affect DM intake, animal performance, and carcass characteristics, thereby suggesting that the use of 10% of CP in diets for finishing bulls reduces their environmental impact due to a lower urinary N excretion than 12 and 14% CP-based diets. Animals that were fed 10, 12, and 14% CP diets had emissions equivalent to 3893; 3755; and 4255 g d −1 of CO 2 , respectively, and no difference was observed among diets. Furthermore, methane emission is not affected by CP levels ranging between 10 to 14% which, on average, is 16.3 g kg −1 of DM intake. Our study found that a decreased CP level did not influence animal performance, but it did decrease N losses in manure without affecting methane emissions. However, it is important to highlight that more studies are necessary to confirm these results. [ABSTRACT FROM AUTHOR]

Abstract: Nineteen sheep averaging 56kg of initial body weight were used in a completely randomized design to investigate the effects of feeding Ca(OH)2-treated (40g/kg, on fresh matter basis) or untreated castorseed meal (CSM) sources on intake, total tract digestibility, hepatic function, and microbial protein synthesis and efficiency. Animals were maintained in metabolic crates for 21 days with 16 days for diet adaptation and 5 days for data and samples collection. Sheep were fed once daily experimental diets containing one of the following 5 protein supplements (150g/kg of the diet DM): (1) soybean meal (SBM); (2) solvent CSM (SCM); (3) SCM treated with Ca(OH)2 (TSCM), expeller CSM (ECM); or ECM treated with Ca(OH)2 (TECM). Treating SCM and ECM with Ca(OH)2 reduced the ricin concentration in 63% leading to an average decrease from 2.46 to 1.06g/kg of BW in the ricin daily intake (P <0.001). No clinical symptoms of ricin intoxication were observed and the serum concentrations of the enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST), which are indicators of hepatic function, were not changed across diets (P >0.05). There was no effect of diets on intake of nutrients (P >0.05) with the exception of non-fibrous carbohydrates (NFC) intake, which was greater (P =0.029) in sheep fed SBM vs. CSM diets and that of ether extract, which was lower (P =0.049) in sheep fed solvent CSM diets vs. expeller CSM diets. However, treating SCM and ECM with Ca(OH)2 tended to increase intakes of DM, CP and NFC. Apparent total tract digestibility of nutrients was not affected by diet (P >0.05) with the exception of ether extract digestibility, which was lower in sheep fed SBM vs. CSM diets (P =0.001) but greater (P =0.023) in sheep fed solvent CSM diets vs. expeller CSM diets. Treating SCM and ECM with Ca(OH)2 increased or tended (0.05> P >0.10) to increase the apparent total tract digestibility of nutrients with the exception NFC. Microbial protein synthesis (P =0.013) and microbial efficiency expressed either as g of microbial CP per g of CP intake (P =0.043) or as g of microbial CP per g of rumen-degradable CP intake (P =0.030) were all increased by treating SCM and ECM with Ca(OH)2. Despite the increase (P =0.022) in the urinary excretion of urea-N (g/day) by treating SCM and ECM with Ca(OH)2, the greater microbial efficiency reduced (P =0.021) fecal-N losses expressed as proportion of N intake numerically increasing retained-N by 21.3%. Treating SCM and ECM with 40g of Ca(OH)2/kg did not completely denaturate ricin but increased microbial protein synthesis and the efficiency of N and energy by ruminal microbes with no detrimental effect on the hepatic function of sheep. [Copyright &y& Elsevier]

Abstract: Ricin is a toxic protein found in castorseed (Ricinus communis L.). We hypothesized that ruminal microbiota are capable of degrading ricin, and that the toxin inhibits ruminal microbial growth. Therefore, first we evaluated the in vitro ruminal degradation of ricin from solvent castorseed meal (SCM) by SDS-PAGE and densitometry analysis of culture medium (Experiment 1). Culture medium (three replicates) were collected after 0, 3, 6, 12, 24 and 48h of incubation content initially 0, 61, 122 and 244μg of ricin/mL or 122μg of ricin/mL (without ruminal inoculum). No protein compounds were detected by SDS-PAGE in the culture medium without ricin, indicating an absence of interference from the ruminal inoculum. Ricin chains remained intact in the absence of rumen inoculum, but they were degraded at rates of 0.2725, 0.1504 and 0.0648h−1 with ruminal inoculum, at initial ricin concentrations of 61, 122 and 244μg/mL. Next, the effect of ricin denaturation on rumen microbial specific growth rate (SGR) (OD-600nm) and the average ammonia concentration at the same time of incubation were investigated (Experiment 2). This experiment had a completely randomized design in a 3×3 factorial (three replicates) arrangement, with three sources of protein (trypticase-control; crude extract of soluble protein at pH 3.8 buffer of solvent castorseed meal (CEP) intact, containing 1.46mg of ricin/mL; and denatured CEP with calcium oxide, containing 0.04mg of ricin/mL) and three protein levels (0.42, 0.84, and 1.68mg/mL). There was interaction (P=0.021) between protein level and protein source for SGR. A linear increase (P<0.001) of SGR was observed with increase of trypticase level, but there was a quadratic effect (P=0.023) with increase of intact CEP level, with a minimum value of SGR of −0.004h−1 at a protein level of 1.45mg/mL (210μg of ricin/mL) of intact CEP. There was no effect (P=0.099) of denatured CEP level, but SGR increased (P<0.001) 3.2 times with denaturation of intact CEP. Ruminal microbial growth was inhibited by 50% with 89μg of ricin/mL. Ammonia concentration was 91% lower (P<0.001) for the CEP source when compared to trypticase, but the denaturation of intact CEP had no effect (P=0.9560) on the ammonia concentration. Although ruminal microbiota was able to degrade ricin in in vitro conditions, the toxin inhibits ruminal microbial growth. Therefore, complete detoxification of CSM before using it to feed ruminants is recommended. The denatured CEP presents potential of use as modifier of rumen microbial fermentation. [Copyright &y& Elsevier]

Abstract: These experiments were carried out to evaluate, using in vitro and in situ techniques, the effects of three inclusion levels of calcium oxide (0, 5, and 10g/kg of sugarcane fresh matter) and four exposure times (0, 24, 48, and 72h) of sugarcane to calcium oxide on the chemical composition and digestive kinetic parameters of sugarcane. The treatments were arranged in a 3 by 4 factorial design. Freshly-cut sugarcane (whole plant) was treated with calcium oxide and separated into 12 piles inside a barn to prevent direct exposure to sunlight, rain, and wind. Every day, before and after animal feeding, the calcium oxide was proportionally hand-mixed with approximately 150kg of freshly-cut sugarcane to make up the dietary treatments. The lowest (Ti) and greatest (Ts) temperature and pH of the treated sugarcane piles were measured immediately before and after sampling, respectively. The ether extract (EE) and DM were not affected (P>0.05) by either exposure time or inclusion level. However, CP increased linearly (P=0.01) and OM decreased linearly (P<0.0001) as the exposure time and calcium oxide inclusion level increased. Interactions between inclusion level and exposure time on DM, OM, CP, EE, Ti, and Ts were not observed. However, significant interactions were detected for non-fibre carbohydrate (NFC), neutral detergent fibre (aNDF), and pH. A quadratic effect of exposure time on the Ti and Ts was observed (P=0.001 and P=0.001, respectively). The maximum temperature was reached with approximately 51h of exposure time. Calcium oxide positively affected the insoluble potentially digestible fraction of sugarcane DM and aNDF (P=0.001 and P=0.001, respectively), and the indigestible fraction of sugarcane aNDF (P=0.001). Interactions between inclusion level and exposure time on soluble and indigestible fractions of sugarcane DM (P=0.0001 and P=0.01, respectively) were found. However, no interactions (P>0.27) were found between inclusion level and exposure time on aNDF digestive kinetic parameters. The fractional digestion rate (kd) of sugarcane DM and aNDF was not influenced by treatments (P>0.05). The mean values of kd for sugarcane DM and aNDF were 0.0235 and 0.0215/h, respectively. The gas production kinetics parameters were not affected (P>0.05) by treatments. In conclusion, the inclusion of calcium oxide improved the in situ potentially digestible fraction of sugarcane DM and aNDF; however, it did not influence the fractional digestion rate. No effects were observed on the in vitro digestive kinetic parameters. [Copyright &y& Elsevier]