Residual feed intake (RFI) describes an animal’s feed efficiency independent of growth performance. The objective of this study was to determine differences in growth performance, carcass traits, major bacteria attached to ruminal solids-fraction, and ruminal epithelium gene expression between the most-efficient and the least-efficient beef cattle. One-hundred and forty-nine Red Angus cattle were allocated to three contemporary groups according to sex and herd origin. Animals were fed a finishing diet in confinement for 70 d to determine the RFI category for each. Within each group, the two most-efficient (n = 6; RFI coefficient = − 2.69 ± 0.58 kg dry matter intake (DMI)/d) and the two least-efficient animals (n = 6; RFI coefficient = 3.08 ± 0.55 kg DMI/d) were selected. Immediately after slaughter, ruminal solids-fraction and ruminal epithelium were collected for bacteria relative abundance and epithelial gene expression analyses, respectively, using real-time PCR. The most-efficient animals consumed less feed (P = 0.01; 5.03 kg less DMI/d) compared with the least-efficient animals. No differences (P > 0.10) in initial body weight (BW), final BW, and average daily gain (ADG) were observed between the two RFI classes. There were no significant RFI × sex effects (P > 0.10) on growth performance. Compared with the least-efficient group, hot carcass weight (HCW), ribeye area (REA), and kidney, pelvic, and heart fat (KPH) were greater (P ≤ 0.05) in the most-efficient cattle. No RFI × sex effect (P > 0.10) for carcass traits was detected between RFI groups. Of the 10 bacterial species evaluated, the most-efficient compared with least efficient cattle had greater (P ≤ 0.05) relative abundance of Eubacterium ruminantium, Fibrobacter succinogenes, and Megasphaera elsdenii, and lower (P ≤ 0.05) Succinimonas amylolytica and total bacterial density. No RFI × sex effect on ruminal bacteria was detected between RFI groups. Of the 34 genes evaluated in ruminal epithelium, the most-efficient cattle had greater (P ≤ 0.05) abundance of genes involved in VFA absorption, metabolism, ketogenesis, and immune/inflammation-response. The RFI × sex interactions indicated that responses in gene expression between RFI groups were due to differences in sex. Steers in the most-efficient compared with least-efficient group had greater (P ≤ 0.05) expression of SLC9A1, HIF1A, and ACO2. The most-efficient compared with least-efficient heifers had greater (P ≤ 0.05) mRNA expression of BDH1 and lower expression (P ≤ 0.05) of SLC9A2 and PDHA1. The present study revealed that greater feed efficiency in beef cattle is associated with differences in bacterial species and transcriptional adaptations in the ruminal epithelium that might enhance nutrient delivery and utilization by tissues. The lack of RFI × sex interaction for growth performance and carcass traits indicates that sex may not play a major role in improving these phenotypes in superior RFI beef cattle. However, it is important to note that this result should not be considered a solid biomarker of efficient beef cattle prior to further examination due to the limited number of heifers compared with steers used in the study.

Pregnancy and early life are critical periods of plasticity during which the fetus and neonate may be influenced by environmental factors such as nutrition. Maternal methionine (Met) supply in non-ruminants during pregnancy can affect offspring development and growth. Thus, the objective of this study was to investigate if increasing Met supply during late-pregnancy affects developmental parameters of the calf at birth and if either maternal Met or colostrum from Met-fed cows alters calf growth. Calves born to Holstein cows individually-fed a basal control [CON; 1.47 Mcal/kg dry matter (DM) and 15.3% crude protein] diet with no added Met or CON plus ethylcellulose rumen-protected Met (MET; Mepron® at 0.09% of diet DM; Evonik Nutrition & Care GmbH, Germany) during the last 28 ± 2 d of pregnancy were used. A total of 39 calves were in CON (n = 22 bulls, 17 heifers) and 42 in MET (n = 20 bulls, 22 heifers). At birth, calves were randomly allocated considering dam treatment and colostrum as follows: 1) calves from CON cows and colostrum from CON cows (n = 21); 2) calves from CON cows and colostrum from MET cows (n = 18); 3) calves from MET cows and colostrum from MET cows (n = 22); and 4) calves from MET cows and colostrum from CON cows (n = 20). All calves were housed, managed, and fed individually during the first 9 wk of life. Despite greater daily DM intake pre-partum in cows fed MET (15.7 vs. 14.4 ± 0.12 kg/d, P < 0.05), colostrum quality and quantity were not affected by maternal diet. At birth, MET calves had greater (P ≤ 0.05) body weight (BW, 44.1 vs. 42.1 ± 0.70 kg), hip height (HH, 81.3 vs. 79.6 ± 0.53 cm) and wither height (WH, 77.8 vs. 75.9 ± 0.47 cm). In contrast, concentrations of His, Lys, and Asn in plasma were lower (P ≤ 0.05) in MET calves. Regardless of colostrum source, the greater BW, HH, and WH in MET calves at birth persisted through 9 wk of age resulting in average responses of + 3.1 kg BW, + 1.9 cm HH, and + 1.8 cm WH compared with CON. Average daily gain during the 9 wk was (P < 0.05) 0.72 ± 0.02 kg/d in MET compared with 0.67 ± 0.02 kg/d in CON calves. Respiratory scores were normal and did not differ (P > 0.05) due to maternal Met supply or colostrum source. However, fecal scores tended to be lower (P ≤ 0.10) in MET calves regardless of colostrum source. Increasing the maternal supply of MET during late-pregnancy enhanced growth in utero as well as during the pre-weaning and early post-weaning periods. Although the ~ 1 kg/d greater DM intake during the last 2–3 wk prior to parturition could explain a portion of the 2 kg extra body mass of MET calves at birth, other mechanisms potentially encompassing nutrient assimilation efficiency likely played a role. Assessing the exact mechanisms sensitive to supply of Met or total amino acid supply during the latter stages of growth in utero merit further research.

Isolated PMNL from neonatal calves were used to evaluate the effect of Met, choline, and taurine supplementation on mRNA expression of genes related to the Met cycle and innate immunity. Five neonatal Holstein calves (3 wk old) were used for PMNL isolation and in vitro culture. The selected genes were related to the 1-carbon and Met cycles, cell signaling and cytokine mediators, inflammation, antimicrobial and killing mechanism associated genes, immune mediators, adhesion, and pathogen recognition. The results indicated that supplementation of Met, choline, and taurine increased homocysteine synthesis through upregulation of SAHH. Furthermore, the lower expression of CXCR1, IL10, IL6, IRAK1, NFKB1, NR3C1, SELL, TLR4, and TNFA indicated that all treatments mitigated the inflammatory activation of blood PMNL. As indicated by the modulation of GCLC and GPX1, choline and taurine supplementation also affected the antioxidant system. However, data indicate that oversupplementation could alter the inflammatory and oxidative status, suggesting the existence of cytotoxicity thresholds. Overall, multiple biological processes in calf PMNL related to inflammatory response and cytoprotection against oxidative stress were affected by Met, choline, and taurine supplementation. These data underscore an important role of these compounds in pre-weaning calf nutritional management.

Extensive degradation of amino acids in the rumen via microbial deamination decreases the post-ruminal availability of dietary indispensable amino acids. Together with the normal decrease in voluntary dry matter intake (DMI) around parturition in dairy cows, microbial metabolism contributes to a markedly negative balance of indispensable amino acids, including methionine which may be the first-limiting for milk production. The main objective of the current study was to profile changes in major bacterial species with key functions in cellulose and hemicellulose digestion, xylan breakdown, proteolytic action, propionic acid production, lactate utilization and ruminal biohydrogenation in cows supplemented with rumen-protected Methionine (SM; Smartamine M, Adisseo NA, Alpharetta, GA, USA) from −23 through 30 d relative to parturition. Because ~90% of the methionine in SM bypasses the rumen, ~10% of the methionine is released into the rumen and can be utilized by microbes. As expected, there was an increase in overall DMI after parturition (Day, P < 0.05) during which cows consumed on average 19.6 kg/d versus 13.9 kg/d in the prepartum period. The postpartum diet contained greater concentrations of lipid and highly-fermentable carbohydrate from corn grain, which likely explains the increases in the relative abundance of Anaerovibrio lipolytica, Megasphaera elsdenii, Prevotella bryantii, Selenomonas ruminantium, Streptococcus bovis, and Succinimonas amylolytica. Despite similar DMI prepartum, cows fed SM had greater (Treatment × Day, P < 0.05) abundance prepartum of Fibrobacter succinogenes, Succinimonas amylolytica, and Succinivibrio dextrinosolvens. However, the greater DMI in cows fed SM after parturition (19.6 kg/d versus 13.9 kg/d) was associated with lower abundance of Fibrobacter succinogenes (2.13 × 10−3 versus 2.25 × 10−4) and Selenomonas ruminantium (2.98 × 10−1 versus 4.10 × 10−1). A lower abundance (Day, P < 0.05) was detected on d 20 compared with d −10 for Fibrobacter succinogenes and Succinivibrio dextrinosolvens. The relative abundance of Butyrivibrio proteoclasticus and Eubacterium ruminantium was stable across treatment and time. In diets with proper balance of rumen-degradable protein and fermentable carbohydrate, the small fraction of Methionine released from the rumen-protected supplement did not seem to compromise growth of major bacterial species in the rumen. In fact, it had a positive effect on 3 major species prepartum when DMI was similar between groups. Because the actual requirements of Methionine (and Lysine, for example) by the cow during the transition period are unknown, it appears warranted to study the rumen microbiome as it relates to supply of rumen-protected amino acids.

This experiment was carried out to determine the effect of blindfold and tail bend during restraint of Egyptian buffaloes on behavioural reactivity and physiological responses to stressful handling procedures. Twenty-four buffalo bulls, naïve to the testing situation, were arbitrarily assigned to either blindfold (visual restriction) (BF), tail bending (physical control) (TB) or control (CT) (no visual restriction or physical control) treatment during restraint. For three minutes each, during veterinary procedures animals entered the squeeze chute and were subjected to testing trials. Heart rate (HR), respiratory rate (RR) and various behaviours of reactivity were recorded. Average HR and RR decreased in both TB and BF bulls but the reduction was greater in BF bulls. Use of the blindfold and tail bend decreased behavioural indicators of reactivity including: chest chute forcing, head move, kicking and struggling. The reduction was greater in BF bulls in the case of use of the chest chute and struggling. Both tail bend and blindfolded buffaloes decreased behavioural and physiological indicators of stress but BF appeared more beneficial, and may therefore be recommended to reduce stress accompanying routine veterinary examination of buffaloes.