Globally, there are approximately one billion beef cattle, and compared with poultry and swine, beef cattle have the poorest conversion efficiency of feed to meat. However, these metrics fail to consider that beef cattle produce high-quality protein from feeds that are unsuitable for other livestock species. Strategies to improve the efficiency of beef cattle are focusing on operational and breeding management, host genetics, functional efficiency of rumen and respiratory microbiomes, and the structure and composition of feed. These strategies must also consider the health and immunity of the herd as well as the need for beef cattle to thrive in a changing environment. Genotyping can identify hybrid vigor with positive consequences for animal health, productivity, and environmental adaptability. The role of microbiome–host interactions is key in efficient nutrient digestion and host health. Microbial markers and gene expression patterns within the rumen microbiome are being used to identify hosts that are efficient at fibre digestion. Plant breeding and processing are optimizing the feed value of both forages and concentrates. Strategies to improve the efficiency of cattle production are a prerequisite for the sustainable intensification needed to satisfy the future demand for beef.

Solute carrier family 11-member A1 (SLC11A1) gene encodes natural macrophage resistance-associated protein which regulates activity of macrophages against intracellular pathogens. The objective of this study was to study the polymorphism in the microsatellites present at 3′ untranslated region (UTR) of the SLC11A1 gene in 113 Zhongdian Yellow cattle (Bos taurus). Using DNA bi-directional sequencing, we detected seven alleles (GT10–16) for the first microsatellite (MS1), five alleles (GT12–16) for MS2, and four alleles (GT4–7) for MS3. MS3 is studied for the first time and revealed four novel variants (alleles GT4–7). Alleles GT12 (45.1%), GT13 (59.3%), and GT5 (85.4%) were the most frequent alleles at MS1, MS2, and MS3, respectively, Genotypes G12/12, G13/13, and G5/5 had the highest frequency 0.239, 0.540, and 0.743 at MS1, MS2, and MS3, respectively. Haplotypic data revealed that GT12/GT13 was the most frequent haplotype observed followed by GT12/14 haplotype. Three nucleotide variations were observed in MS1 and MS2. Comparative analysis of GT12/GT12 and GT13/GT13 genotype with other bovine genotypes showed significant difference (P > 0.05). Our results suggest that the homozygous genotypes GT12/GT12 and GT13/GT13 in Zhongdian Yellow cattle might be related to disease resistance. The findings reported in this study would be helpful in cattle breeding programs.

Over 2 yr, yearling steers (n = 200) were used to evaluate growth performance, carcass, meat quality, and nutrient composition traits as affected by management regimen comparing three methods of forage finishing (alfalfa pasture, hay, and silage) versus a high corn diet. Management regimen × year interactions (P < 0.01) for average daily gain, dry matter intake, gain-to-feed, carcass weight, and grade fat were due to lower performance for hay-fed cattle in years 1 vs. 2. Carcass, meat quality, and taste panel traits were generally similar (P > 0.10) across method of forage finishing. Trained taste panels found longissimus muscle from grain-fed beef to be more (P < 0.01) tender, juicy, and flavourful than forage finished beef, with lower (P ≤ 0.05) ratings for tenderness and juiciness for hay- vs. silage-finished beef. Corn finished beef contained greater amounts of oleic and monounsaturated fatty acids and lower amounts of omega-3 and polyunsaturated fatty acids than forage finished beef (P ≤ 0.04). Although the method of forage finishing may not affect most performance, carcass, and meat quality (pH, colour, intramuscular fat content, and shear force) traits, there may be concerns with tenderness and juiciness for beef from cattle finished on alfalfa hay.

Pregnant beef cows (56; 727 ± 102 kg body weight) in their second trimester were used to examine black spruce (BSP) needles and branches for replacing alfalfa silage in wintering cow diets. Five dietary treatments assessed BSP inclusion rates (0%, 15%, 22.5%, 30%, and 37.5% in the diet) for 92 d up until 2 wk before start of calving using a randomized complete block design (10–12 cows per treatment). There were linear decreases (P < 0.001) in total weight gain, average daily gain, and dry matter intakes (DMI) as amounts of dietary BSP increased. Low DMI feeding BSP may be attributed to palatability issues and lower rates of digestion. Changes in body condition score increased (P < 0.003) as dietary BSP increased. These effects are supported by corresponding linear decreases (P < 0.001) for changes in rump fat cover and increases (P < 0.001) in serum non-esterified fatty acids as dietary BSP increased. After feeding the test diets, there were no dietary treatment differences (P > 0.42) for calf birth and weaning weights as well as cow pregnancy and culling rates. Based on this study, incorporation of BSP into gestating cow diets cannot be recommended.

The objective of this study was to determine the effects of feeding barley silage (BS) or corn silage (CS) with dry-rolled barley (BG), dry-rolled corn (CG), or a blend of barley and corn grain (BCG), on growth performance and nutrient digestibility, the latter predicted using near-infrared spectroscopy for backgrounding cattle. Steers (n = 288) were stratified by body weight (BW) into 24 pens and pens were randomly assigned to one of six treatments (n = 4) in a 2 × 3 factorial design. Main factors included BS or CS in combination with BG, CG, or BCG. There were no silage × grain interactions. Dry matter intake (DMI; P = 0.018) and final BW (P = 0.004) were greater for steers fed CS than BS, but average daily gain (1.01 kg d⁻¹) and gain-to-feed ratio (0.10 kg kg⁻¹) were not affected by silage or grain source. Steers fed CS also had greater dry matter, organic matter, crude protein (CP), acid detergent fiber (ADF), starch, and gross energy digestibility values (P < 0.01) than BS. Feeding BG increased starch, neutral detergent fiber, ADF, and CP digestibility values (P ≤ 0.01) over CG and BCG. Relative to BS, feeding CS increased DMI, final BW, and nutrient digestibility, whereas dry-rolled BG improved nutrient digestibility when compared with CG and BCG in backgrounding diets.

The objectives of this study were to quantify the effect of post-weaning residual feed intake (RFI) on subsequent grazed forage intake, methane (CH₄), and carbon dioxide (CO₂) emissions. Beef heifers classified for RFI adjusted for off-test backfat (RFI_fat; 55 high and 56 low) at 9 mo of age were monitored 7 mo later for CH₄ and CO₂ emissions using the GreenFeed Emissions Monitoring system. About 56 of these heifers were also monitored as high and low RFI_fat groups using open-path Fourier-transform infrared spectroscopy (OP-FTIR). Heifers were dosed with 1 kg of C₃₂-labelled pellets once daily for 15 d, with twice daily fecal sampling the last 8 d to determine individual grazed forage intake using the n-alkane method. Low RFI_fat pregnant heifers consumed less forage (10.25 vs. 10.81 kg dry matter d⁻¹; P < 0.001), and emitted less daily CH₄ (238.7 vs. 250.7 g d⁻¹; P = 0.009) and CO₂ (7578 vs. 8041 g d⁻¹; P < 0.001) compared with high RFI_fat animals. Results from the OP-FTIR further confirmed that low RFI_fat heifers emitted 6.3% less (g d⁻¹; P = 0.006) CH₄ compared with their high RFI_fat cohorts. Thus, selection for low RFI_fat will decrease daily CH₄ and CO₂ emissions from beef cattle.

The objective of this study was to determine the early responses to a moderate concentrate increase in cattle diets with regards to various behavioral and physiological responses in cattle. Eight ruminally cannulated Angus crossbred beef heifers were adapted to a 70% concentrate diet (T70) and then switched to a 90% concentrate diet (H90). Measurements of feeding behavior, ruminal pH and temperature, rumen motility, liquid passage rate, and blood acid–base status were conducted on T70 as well as first day (d1) and second day (d2) of high-grain H90feeding to monitor the beginning of the transition period. Ruminal pH was below 5.6 for longer on both days of H90 compared with T70, suggesting animals experienced subacute ruminal acidosis while switching from T70 to H90. Transitioning did not affect dry matter intake (DMI). Eating rate during meals was reduced on d1 and d2 H90 compared with T70. Ruminal contraction amplitude was reduced on both days of H90 feeding. Contraction duration was reduced on d1 H90, and returned to T70 values by d2 H90. Results indicated that a moderate transition to a finishing diet influenced feeding behavior and reduced rumen motility at the beginning time after transition, but did not influence voluntary DMI.

A total of 28 piglets weaned at 21 d of age (6.94 ± 0.28 kg of body weight) were assigned to one of four dietary treatments for 14 d: (1) negative control (NC; a corn–wheat–soybean meal diet), (2) positive control [PC; NC + 0.025% antimicrobial growth promoter (AGP)], (3) ROD2 [2% red-osier dogwood (ROD)], and (4) ROD4 (4% ROD). All pigs were orally inoculated with Escherichia coli K88⁺ on day 8. The pre-planned orthogonal test was performed to compare (1) NC vs. PC and (2) NC vs. ROD. The inclusion of ROD in a nursery diet increased (P < 0.05) superoxide dismutase (SOD) activities and decreased (P < 0.05) malondialdehyde (MDA) concentrations in the serum. Moreover, pigs fed with ROD diets had shallower (P < 0.05) crypt depth and higher (P < 0.05) villus height to crypt depth ratio than those fed the NC diet. Dietary AGP supplementation reduced (P < 0.05) the MDA concentration in the ileum and serum at 24 h after challenge, and improved (P < 0.01) the SOD activities in the serum. In conclusion, the inclusion of ROD in a nursery diet enhanced the antioxidative defense system and intestinal morphology, showing comparable effects with AGP supplementation.

Characteristics of wheat and barley inoculated with a homo-fermentative (HO) or hetero-fermentative (HE) lactic acid bacteria (LAB) were investigated in separate 97 d studies conducted using a 3 × 2 factorial arrangement comparing inoculants (no inoculant, HO or HE) and multi-enzyme (no or yes) addition. The pH declined (P < 0.05) to below 4.5 by day 6, coinciding with peaks in lactobacilli and yeast counts. A more rapid decline (P < 0.05) in pH and lactobacilli count but higher (P < 0.05) yeast count was observed with HO relative to HE. Enzyme addition reduced pH in inoculated grains only, particularly with HE (inoculant × enzyme effect; P < 0.05). Higher dry matter losses (P < 0.05) were observed with HE, most apparent in barley. Lactate was generally highest in HO and was increased by enzyme addition. Acetate was higher (P < 0.05) in HE. Ethanol and ammonia were lowest (P < 0.05) in HO. Wheat neutral detergent fibre (NDF) was reduced by both inoculants compared with control, whereas enzyme addition reduced NDF content in both grains. In conclusion, although not marked, fermentation responses appeared greater in wheat than barley although either LAB inoculant improved grain fermentation characteristics. The multi-enzyme appeared active during fermentation.

This study was conducted to investigate the effects of increasing dietary net energy (NE) density manipulated by either dietary fat or fibre content on growth performance and energy intake in weaned pigs. A total of 60 barrows (8.40 ± 0.91 kg) were randomly allotted to one of five dietary treatments based on initial body weight. The experimental diets contained increasing NE densities (i.e., 9.9, 10.3, and 10.7 MJ NE kg⁻¹) by manipulating either dietary fat or fibre content. Feeding the different dietary treatments did not affect growth performance among dietary treatments. The apparent total tract digestibility of dry matter, gross energy, fat, and neutral detergent fibre of the diets linearly increased (P < 0.05) for weeks 1–3 as dietary NE densities increased. Digestible energy (DE) and NE intake linearly increased (P < 0.01) with increasing dietary NE densities manipulated by dietary fibre content for weeks 2 and 3. A tendency (P = 0.06) for a linear increase in DE and NE intake was observed for weeks 2 and 3 when dietary NE densities were manipulated by fat content. In conclusion, weaned pigs were not able to adjust feed intake in response to dietary NE densities ranging from 9.9 to 10.7 MJ kg⁻¹.

An experiment was conducted to determine the effects of feeding highly condensed tannin legume (sericea lespedeza, SL; Lespedeza cuneata) forage on gastrointestinal tract microbial counts and meat quality in goats. Intact male Spanish kids were kept in 0.40 ha paddocks of SL, bermudagrass (BG; Cynodon dactylon; control), or a combination of SL + BG (n = 10 goats per treatment group) for 8 wk. All goats were supplemented with a commercial feed pellet at 0.45 kg·head⁻¹·d⁻¹ for the first 4 wk and 0.23 kg·head⁻¹·d⁻¹ for the final 4 wk of the trial. At the end of the experiment, half the goats from each paddock were subjected to 3 h transportation stress, then all animals were humanely slaughtered. Diet or stress did not have a significant effect on skin Escherichia coli, coliform, or aerobic plate counts, and carcass, rumen, and fecal bacterial counts. Muscle pH at 24 h postmortem tended (P = 0.06) to be higher in transported compared with non-transported goats. The results indicate that SL consumption by goats for 8 wk did not significantly affect gastrointestinal tract, skin, and carcass microbial counts or meat quality, although preslaughter stress could influence meat quality due to changes in the course of postmortem pH decline.

The goal of this study was to estimate genetic parameters and predict direct and correlated response to selection for lamb growth traits and ewe reproductive traits, based on single-trait selection or combining multiple traits in an optimum index that targets total litter post-weaning weight in the first lambing as the main selection goal. Heritability estimates ranged from 0.04 to 0.19. Genetic correlations between growth and reproductive traits ranged from ?0.24 to 0.15. The indirect response to selection for reproductive traits in later lambings, by selecting on first lambing performance, was 11% – 25% greater than direct selection. The response to indirect selection for composite reproductive traits, i.e.,total weaning weight or total post-weaning weight, by selecting on individual lamb weaning weight or post-weaning weight was 1% – 69% greater than direct selection, but it was accompanied by a negative response on litter size. However, combining alternate growth and reproductive traits in optimum selection index resulted in correlated response of up to 96% greater than direct selection response for reproductive traits without a negative response on litter size. Therefore, multiple trait selection using an index of component traits was more effective than direct selection for a composite trait.

Effects of Saccharomyces cerevisiae fermentation products (SCFP) and subacute ruminal acidosis (SARA) on rumen and hindgut fermentation, feed intake, and total tract nutrient digestibilities were determined in 32 lactating Holstein cows between weeks 4 and 9 of lactation. Treatments included control, 14 g·d⁻¹ Diamond V Original XPC™ (SCFPa; Diamond V, Cedar Rapids, IA, USA), 19 g·d⁻¹ NutriTek^® (SCFPb-1X; Diamond V), and 38 g·d⁻¹ NutriTek^® (SCFPb-2X; Diamond V). During weeks 5 and 8, SARA challenges were conducted by switching from a 18.6% to a 27.9% dry matter (DM) starch diet. This reduced the rumen and feces pH. The durations of the rumen pH below 5.6 during these challenges averaged 175.0, 233.8, 246.9, and 79.3 min·d⁻¹ for the control, SCFPa, SCFPb-1X, and SCFPb-2X treatments, respectively. Hence, SARA was not induced under the SCFPb-2X treatment. The feces pH during the SARA challenges was lowest during SCFPb-2X, suggesting this treatment shifted fermentation from the rumen to the hindgut. The SARA challenges reduced the total tract digestibility of DM, neutral detergent fiber digestibility (NDFd), and phosphorus, but tended to increase that of starch. The SCFPb-2X treatment increased the NDFd from 52.7% to 61.8% (P < 0.05). The SCFPb-2X treatment attenuated impacts of SARA.

The genetic architecture of dark cutting was investigated with a case-control genome-wide association study on two groups of beef cattle analyzed separately and together (combined group). Groups I (n = 64) and II (n = 150) were genotyped using the 70K GeneSeek Genomic Profiler for Beef Cattle-HD and the 50K Illumina BovineSNP50v2 BeadChip, respectively. Dark cutting was analyzed as a binary trait (case versus control) using logistic regression in an additive model implemented in PLINK version 1.9. Significant loci were not identified when correcting for multiple testing (false discovery rate), suggesting that the trait is not controlled by genes with big effects, or the sample size was not large enough to detect these major genes. Regions harbouring single-nucleotide polymorphisms (SNPs) with a raw p < 0.01 using 1 MB window were analyzed for gene function using the ingenuity pathway analysis. For groups I, II, and the combined group, 449, 301, and 191 SNPs were identified, respectively. Genes identified were involved in pyruvic acid modification and release, 2-deoxyglucose clearance and disposal, sucrose recognition, energy production, and metabolism of carbohydrate. Although detected SNP associations require validation in a large population, results suggested the possibility for marker-assisted or genomic selection of beef cattle to reduce dark cutting.

Effects of feeding ISA brown and Shaver white breeders sources of n-3 fatty acids (FA) on egg components, apparent embryonic uptake (AEU) of egg components, and hatching body composition were examined. A total of 240 females and 30 males per each strain were fed either: (1) control (CON); (2) CON + 1% of dried microalgae (DMA), as a source of docosahexaenoic acid; or (3) CON + 2.60% of dry extruded product consisting of full-fat flaxseed (FFF), as a source of α-linolenic acid for 30 d. Eggs were incubated and the residual yolks (RY) sampled at hatch for AEU of dry matter (DM), minerals, and organic matter (OM). Feeding n-3 FA sources reduced the AEU of OM and minerals resulting in a higher ratio of RY to body weight (P = 0.002). Feeding FFF increased body fat and decreased lean in Shaver white hatchlings compared with CON (P < 0.05). The body mineral was reduced by feeding DMA compared with other treatments (P < 0.05). The change in body composition in response to feeding of n-3 sources was associated with the change in AEU of DM, OM, and minerals, not the concentration of these components in the yolk.

This study compared the different residual feed intake (RFI) categories of lactating Holsteins with respect to methane (CH₄) emissions, dry matter intake (DMI, kg), milk somatic cell count (SCC, 10³?mL^?1), and β-hydroxybutyrate (BHB, mmol?L^?1). The RFI was calculated in 131 lactating Holstein cows that were then categorized into ?RFI (RFI < 0) vs. +RFI (RFI > 0) and low- [RFI < ?0.5 standard deviation (SD)] vs. high-RFI (RFI > 0.5 SD) groups. Milk traits were recorded in 131 cows, whereas CH₄ and carbon dioxide were measured in 83. Comparisons of ?RFI vs. +RFI and low- vs. high-RFI showed 7.9% (22.3 ± 0.40 vs. 24.2 ± 0.39) and 12.8% (21.1 ± 0.40 vs. 24.2 ± 0.45) decrease (P < 0.05) in DMI of ?RFI and low-RFI groups, respectively. Similarly, ?RFI and low-RFI cows had lower (P < 0.05) CH₄ (g?d^?1) by 9.7% (343.5 ± 11.1 vs. 380.4 ± 10.9) and 15.5% (332.5 ± 12.9 vs. 393.5 ± 12.6), respectively. Milk yield was not different (P > 0.05) in ?RFI vs. +RFI and low vs. high comparisons. The ?RFI and low-RFI cows had lower (P < 0.05) SCC in ?RFI vs. +RFI and low-RFI vs. high-RFI comparisons. The BHB was lower (P < 0.05) in low-RFI compared with the high-RFI group. Low-RFI dairy cows consumed less feed, emitted less CH₄ (g?d^?1), and had lower milk SCC and BHB without differing in milk yield.

Sixty-nine finishing steers were randomly assigned to one of two treatment groups: supplementation to provide 0 or 267 mg·d⁻¹ of ractopamine hydrochloride (RAC) for 42 d. Twelve steers were slaughtered for tissue and blood collection. Final body weight (BW) tended to be greater with RAC supplementation. Ractopamine hydrochloride supplementation decreased liver mass as a percentage of BW. Pancreatic protein concentration, digestive enzyme activities, serum glucose, and insulin concentrations were not influenced by RAC supplementation. Ractopamine hydrochloride supplementation decreased the pancreatic:α-amylase:trypsin and serum urea nitrogen concentrations. These data suggest that RAC may influence pancreatic exocrine function in cattle.

The United States Department of Agriculture (USDA) system has five retail cut yield (RCY) classes, whereas the former Canadian system had three total lean yield (TLY) classes. A total of 720 beef carcasses were used to develop a modified grade ruler, harmonizing the Canadian grades into five classes. Beef carcasses (n = 750) from three Canadian federally inspected facilities were graded using both USDA and Canadian (harmonized ruler) systems for external validation. Agreement between the USDA-RCY and the Canadian TLY was high (R² = 0.80). The validation between the harmonized ruler and the USDA-RCY showed a standard deviation of the difference of 1.32 and a coefficient of concordance of 0.83.