Relationship between residual feed intake and digestive traits of fattening bulls fed grass silage- or maize silage-based diets

Several studies tried to identify digestive determinants of individual variation in feed efficiency between fattening bulls, because of their importance for breeding and management strategies. Most studies focused on single traits or single diet. Little is known about diet-dependent differences in digestive determinants and on their relative importance in distinguishing divergent residual feed intake (RFI) bulls. This research aimed (i) to identify digestive traits that differed between bulls diverging in RFI and fed a maize silage- or a grass silage-based diets; (ii) to highlight the relationships between RFI and digestive traits, and (iii) to explore the hierarchy among digestive traits in discriminating RFI divergent bulls. After an initial RFI test of 84 days on 100 Charolais growing bulls fed two different diets based on grass silage (GS), or maize silage (MS), the 32 most RFI divergent bulls were selected (eight efficient RFI- and eight inefficient RFI+ bulls per diet) and measured thereafter for total tract apparent digestibility and transit rate, enteric gas emissions (CH4 and H2), rumen pH, and feeding behaviour. Rumen particle size and visceral organ and reticulo-omasal orifice (ROO) sizes and rumen and ileum histology were measured at slaughter on the 32 selected extreme RFI bulls. Irrespective of the diet, efficient bulls (RFI-) had lower rumen size, CH4 yield (g/kg DM intake; tendency), lower number of cells in the ileal crypts, tended to have longer time of rumen pH below 5.8 and lower proportion of small size particles in rumen content than non-efficient bulls (RFI+). A long-term test for feed efficiency (197 d on average) was performed on the whole experimental period until slaughter for the 100 animals. The long-term RFI value was negatively related to time spent in activity other than ingestion, rumination, and resting, and positively related (tendency) to the duration of ingestion events, to rumen and abomasum size, irrespective of the diet. Diet-dependent effects were noted: with GS, efficient (RFI-) bulls showed a slower transit rate, whereas with MS, efficient (RFI-) bulls tended to have shorter resting events and a smaller ROO than inefficient bulls (RFI+). The transit rate and the ROO size tended to be positively related, while total tract apparent digestibility of nitrogen was negatively related to long-term RFI value, but only in GS. Rumen size appeared as the most discriminating digestive variable between RFI divergent bulls, but this result should be validated on a larger number of animals and diets.

Effects of Alternative Cassava and Taro Feed on the Carcass and Meat Quality of Fattening Pigs Reared under Ecuadorian Backyard Systems

Ecuadorian small producers use crossbred animals with a low level of genetic improvement, which are fed with alternative feeds to decrease production costs. The objective of this study was to evaluate the effects of geographical location and three diets according to the amount of cassava and taro incorporated into the feed (T1 conventional feed; T2 and T3 with 32% and 42% of cassava and taro, respectively) in pigs reared under the backyard system. The results did not show many differences between the treatments for morphological traits; however, between geographical locations, significant differences were evidenced. The fat content from the first rib was higher in the T1 group. The intramuscular fat percentage was higher in the T1 group, contrary to the protein levels, which were higher in the T3 group in Esmeraldas and the T2 group in Ro Chico. In the gastrointestinal tract (GIT) and its attached organs, differences were found in the empty stomach weight, full and empty small intestine weight, liver weight, and total GIT weight, with the T2 and T3 groups having the largest and heaviest. Cassava and taro did not affect the morphometric behavior and quality of the carcass but increased the amount of protein in the meat and the weight of the GIT. Geographical location was also observed to have a significant effect.

Integrated Single-Trait and Multi-Trait GWASs Reveal the Genetic Architecture of Internal Organ Weight in Pigs

Internal organ weight is an essential indicator of growth status as it reflects the level of growth and development in pigs. However, the associated genetic architecture has not been well explored because phenotypes are difficult to obtain. Herein, we performed single-trait and multi-trait genome-wide association studies (GWASs) to map the genetic markers and genes associated with six internal organ weight traits (including heart weight, liver weight, spleen weight, lung weight, kidney weight, and stomach weight) in 1518 three-way crossbred commercial pigs. In summation, single-trait GWASs identified a total of 24 significant single- nucleotide polymorphisms (SNPs) and 5 promising candidate genes, namely, TPK1, POU6F2, PBX3, UNC5C, and BMPR1B, as being associated with the six internal organ weight traits analyzed. Multi-trait GWAS identified four SNPs with polymorphisms localized on the APK1, ANO6, and UNC5C genes and improved the statistical efficacy of single-trait GWASs. Furthermore, our study was the first to use GWASs to identify SNPs associated with stomach weight in pigs. In conclusion, our exploration of the genetic architecture of internal organ weights helps us better understand growth traits, and the key SNPs identified could play a potential role in animal breeding programs.

The effect of feed efficiency classification on visceral organ mass in finishing steers

Individual feed intake of crossbred beef steers (one contemporary group/year, 2 yr) was recorded during finishing to investigate visceral organ mass in steers divergent for feed efficiency. Based on residual feed intake (RFI), the 20% most efficient (HE, n = 8/year) and 20% least efficient (LE; n = 8/year) steers with 12th rib fat ≥1.02 cm were slaughtered. High efficiency steers had less DM intake (P < 0.001), greater G:F (P < 0.001), and similar ADG and hot carcass weight (HCW). High efficiency steers tended to have less (P ≤ 0.10) small intestinal mass (actual and relative to BW and HCW) in year 1. In year 2, HE steers tended to have greater (P ≤ 0.10) large intestinal actual and relative masses. Low efficiency steers tended to have greater (P = 0.06) actual omasum mass and had greater (P ≤ 0.03) relative omasum masses compared with HE. Stomach complex, total gastrointestinal tract, liver, and kidney masses tended to be greater (P ≤ 0.10) relative to BW, and were greater (P ≤ 0.05) relative to HCW, in LE. Data suggest that visceral organ mass, especially of the gastrointestinal tract, plays a role in overall metabolic efficiency of finishing steers.

Identification of Candidate Variants Associated With Bone Weight Using Whole Genome Sequence in Beef Cattle

Bone weight is critical to affect body conformation and stature in cattle. In this study, we conducted a genome-wide association study for bone weight in Chinese Simmental beef cattle based on the imputed sequence variants. We identified 364 variants associated with bone weight, while 350 of them were not included in the Illumina BovineHD SNP array, and several candidate genes and GO terms were captured to be associated with bone weight. Remarkably, we identified four potential variants in a candidate region on BTA6 using Bayesian fine-mapping. Several important candidate genes were captured, including LAP3, MED28, NCAPG, LCORL, SLIT2, and IBSP, which have been previously reported to be associated with carcass traits, body measurements, and growth traits. Notably, we found that the transcription factors related to MED28 and LCORL showed high conservation across multiple species. Our findings provide some valuable information for understanding the genetic basis of body stature in beef cattle.

Transcriptome analysis of long noncoding RNAs ribonucleic acids from the livers of Hu sheep with different residual feed intake

Long noncoding RNAs (LncRNAs), as key regulators, have vital functions in various biological activities. However, in sheep, little has been reported concerning the genetic mechanism of LncRNA regulation of feed efficiency. In the present study, we explored the genome-wide expression of LncRNAs and transcripts of uncertain coding potential (TUCPs) in the livers of sheep with extreme residual feed intake (RFI) using RNA sequencing. We identified 1 523 TUCPs and 1 996 LncRNAs, among which 10 LncRNAs and 16 TUCPs were identified as being differentially expressed between the High-RFI and Low-RFI groups. Co-expression and co-localization methods were used to search for LncRNA and TUCP target genes, which identified 970/1 538 and 23/27 genes, respectively. Ontology and pathways analysis revealed that the LncRNAs/TUCPs that were highly expressed in the Low-RFI group are mostly concentrated in energy metabolism pathways. For example, LNC_000890 and TUCP_000582 might regulate liver tissue metabolic efficiency. The LncRNAs/TUCPs that were highly expressed in the High-RFI group are mostly enriched in immune function pathways. For example, TUCP_000832 might regulate animal health, thereby affecting feed efficiency. Subsequently, a co-expression network was established by applying the expression information of both the differentially expressed LncRNAs and TUCPs and their target mRNAs. The network indicated that differentially expressed genes targeted by the upregulated LncRNAs and TUCPs were mainly related to energy metabolism, while those genes targeted by the downregulated LncRNAs and TUCPs were mainly related to immune response. These results provide the basis for further study of LncRNA/TUCP-mediated regulation of feed efficiency.

Exploring the Regulatory Potential of Long Non-Coding RNA in Feed Efficiency of Indicine Cattle

Long non-coding RNA (lncRNA) can regulate several aspects of gene expression, being associated with complex phenotypes in humans and livestock species. In taurine beef cattle, recent evidence points to the involvement of lncRNA in feed efficiency (FE), a proxy for increased productivity and sustainability. Here, we hypothesized specific regulatory roles of lncRNA in FE of indicine cattle. Using RNA-Seq data from the liver, muscle, hypothalamus, pituitary gland and adrenal gland from Nellore bulls with divergent FE, we submitted new transcripts to a series of filters to confidently predict lncRNA. Then, we identified lncRNA that were differentially expressed (DE) and/or key regulators of FE. Finally, we explored lncRNA genomic location and interactions with miRNA and mRNA to infer potential function. We were able to identify 126 relevant lncRNA for FE in Bos indicus, some with high homology to previously identified lncRNA in Bos taurus and some possible specific regulators of FE in indicine cattle. Moreover, lncRNA identified here were linked to previously described mechanisms related to FE in hypothalamus-pituitary-adrenal axis and are expected to help elucidate this complex phenotype. This study contributes to expanding the catalogue of lncRNA, particularly in indicine cattle, and identifies candidates for further studies in animal selection and management.

Physiological parameter values for physiologically based pharmacokinetic models in food-producing animals. Part I: Cattle and swine

Physiologically based pharmacokinetic (PBPK) models for chemicals in food animals are a useful tool in estimating chemical tissue residues and withdrawal intervals. Physiological parameters such as organ weights and blood flows are an important component of a PBPK model. The objective of this study was to compile PBPK‐related physiological parameter data in food animals, including cattle and swine. Comprehensive literature searches were performed in PubMed, Google Scholar, ScienceDirect, and ProQuest. Relevant literature was reviewed and tables of relevant parameters such as relative organ weights (% of body weight) and relative blood flows (% of cardiac output) were compiled for different production classes of cattle and swine. The mean and standard deviation of each parameter were calculated to characterize their variability and uncertainty and to allow investigators to conduct population PBPK analysis via Monte Carlo simulations. Regression equations using weight or age were created for parameters having sufficient data. These compiled data provide a comprehensive physiological parameter database for developing PBPK models of chemicals in cattle and swine to support animal‐derived food safety assessment. This work also provides a basis to compile data in other food animal species, including goats, sheep, chickens, and turkeys.

Potential Biomarkers for Feed Efficiency-Related Traits in Nelore Cattle Identified by Co-expression Network and Integrative Genomics Analyses

Feed efficiency helps to reduce environmental impacts from livestock production, improving beef cattle profitability. We identified potential biomarkers (hub genes) for feed efficiency, by applying co-expression analysis in Longissimus thoracis RNA-Seq data from 180 Nelore steers. Six co-expression modules were associated with six feed efficiency-related traits (p-value ≤ 0.05). Within these modules, 391 hub genes were enriched for pathways as protein synthesis, muscle growth, and immune response. Trait-associated transcription factors (TFs) ELF1, ELK3, ETS1, FLI1, and TCF4, were identified with binding sites in at least one hub gene. Gene expression of CCDC80, FBLN5, SERPINF1, and OGN was associated with multiple feed efficiency-related traits (FDR ≤ 0.05) and were previously related to glucose homeostasis, oxidative stress, fat mass, and osteoblastogenesis, respectively. Potential regulatory elements were identified, integrating the hub genes with previous studies from our research group, such as the putative cis-regulatory elements (eQTLs) inferred as affecting the PCDH18 and SPARCL1 hub genes related to immune system and adipogenesis, respectively. Therefore, our analyses contribute to a better understanding of the biological mechanisms underlying feed efficiency in bovine and the hub genes disclosed can be used as biomarkers for feed efficiency-related traits in Nelore cattle.

Genetic parameters and genome-wide association study regarding feed efficiency and slaughter traits in Charolais cows

Residual energy intake (REI) on two successive diets (hay and maize based) and slaughter traits, including visceral organs, were phenotyped in 584 adult purebred Charolais cows. To investigate the relationships between these traits and their genetic determinism, we first estimated the genetic parameters, including correlations, using REML modeling under WOMBAT software. The animals were then genotyped on the BovineSNP50 SNPchip before being imputed to the 600K density and genome wide association study was performed with GCTA software. We found low heritability for REI (h2 = 0.12 in each of the diet phases). Although the phenotypic correlation between the two diet phases was moderate (0.36), the genetic correlation was high (0.83), indicating a common genetic determinism for feed efficiency regardless of the diet. Correlations between REI and slaughter traits were negative regarding muscle-related traits and positive for fat-related traits, indicating that efficient animals generally had a more muscular carcass. It was also seen that feed efficiency was genetically and phenotypically correlated with smaller organs when expressed as a proportion of their empty body weight. From the GWAS analysis, seven QTLs were found to be associated with a trait at the genome-wide level of significance and 18 others at the chromosome-wide level. One important QTL was detected in BTA 2, reflecting the essential effect of the myostatin gene on both carcass composition and relative organ weight. Three QTLs were detected for REI during the maize diet phase on BTA 13, 19, and 28, the latter being significant at the genome-wide level. The QTLs on BTA 19 mapped into the TANC2 gene and the QTLs on BTA 28 into the KIF1BP gene, which are both known to interact with the same protein (KIF1A). However, no obvious functional link between these genes and feed efficiency could be made. Among the other QTLs detected, one association on BTA 4 with liver proportion mapped to the candidate gene WASL, which has previously been shown to be differentially expressed in liver cells and linked to feed restriction or cancer development. No QTLs were found to be common between feed efficiency and any slaughter traits.

Relationship between feed efficiency and slaughter traits of French Charolais bulls

Improving feed efficiency is of interest to French beef producers so as to increase their profitability. To enable this improvement through selection, genetic correlations with production traits need to be quantified. The objective of this study was to estimate the genetic parameters for growth, feed efficiency (FE), and slaughter performance of young beef bulls of the French Charolais breed. Three feed efficiency criteria were calculated: residual feed intake (RFI), residual gain (RG), and ratio of FE. Data on feed intake, growth, and FE were available for 4,675 Charolais bulls tested in performance test stations and fed with pelleted diet. Between 1985 and 1989, 60 among 510 of these bulls were selected to procreate one generation of 1,477 progeny bulls which received the same pelleted diet at the experimental farm in Bourges. In addition to feed intake, growth, and FE traits, these terminal bulls also had slaughter traits of carcass yield, carcass composition, and weight of visceral organs collected. Genetic parameters were estimated using linear mixed animal models. Between performance test bulls and terminal bulls, the genetic correlation of RFI was 0.80 ± 0.18; it was 0.70 ± 0.21 for RG and 0.46 ± 0.20 for FE. For carcass traits, RFI was negatively correlated with carcass yield (-0.18 ± 0.14) and muscle content (-0.47 ± 0.14) and positively with fat content (0.48 ± 0.13). Conversely, RG and FE were positively correlated with carcass yield and muscle content and negatively with fat content. For the three FE criteria, efficient animals had leaner carcass. For visceral organs (as a proportion of empty body weight), RFI was genetically correlated with the proportions of the 5th quarter (0.51 ± 0.17), internal fat (0.36 ± 0.14), abomasum (0.46 ± 0.20), intestines (0.38 ± 0.17), liver (0.36 ± 0.16), and kidneys (0.73 ± 0.11). Conversely, RG and FE were negatively associated with these traits. The high-energy expenditure associated with the high-protein turnover in visceral organs may explain this opposite relationship between FE and the proportion of visceral organs. Selection for final weight and RFI increased growth and FE in progeny, and also improved carcass yield and muscle content in the carcass. To conclude, determinations of growth and feed intake in performance test stations are effective to select bulls to improve their growth, FE, and muscle content in carcass.

Effects of ractopamine hydrochloride supplementation on feeding behavior, growth performance, and carcass characteristics of finishing steers. Transl Anim Sci 2019;3:1143-1152. [PMID: 32704878 PMCID: PMC7200486 DOI: 10.1093/tas/txz114]

Ractopamine hydrochloride (RAC) is a β-adrenergic agonist that functions as a repartitioning agent to improve muscling in feedlot cattle. Many studies have investigated the effects of RAC on growth performance and carcass characteristics; however, there is minimal information about the influence of RAC on feeding behavior. Sixty-nine steers (body weight [BW] = 364 ± 3.9 kg) predominately of Angus and Simmental breeding were subjected to a 126-d (n = 46) or 154-d (n = 23) feeding period and randomly assigned to one of two treatment groups: supplementation to provide 0 (CON; n = 34) or 267 ± 4.9 mg/d of RAC (n = 35). Ractopamine was provided as Optaflexx 45 at 0.024% of the diet (dry matter [DM] basis; Elanco Animal Health, Greenfield, IN). Dietary treatments were fed the final 42 d in the feed yard (treatment period). Feeding behavior and growth performance were measured using radio frequency identification tags and the Insentec feeding system. Following the final day of treatment, steers were slaughtered and carcass measurements were recorded. Data were analyzed using MIXED models in SAS. There were no differences in BW, average daily gain (ADG), DM intake (DMI), gain:feed ratio (G:F), or feeding behavior during the pretreatment period (P > 0.44). Ractopamine supplementation increased G:F during the treatment period (P = 0.02) and during the total period (P = 0.03) and tended to increase ADG during the treatment and total period (P ≤ 0.08). DMI was not affected during the treatment or total period (P > 0.67). Eating time per visit, per meal, and per day were decreased (P < 0.02) in steers supplemented with RAC during the treatment period. DMI per minute was increased (P = 0.02) in steers supplemented with RAC. Hot carcass weight, dressing percentage, and 12th rib fat were not influenced by RAC supplementation. Ractopamine supplementation decreased marbling (P = 0.008) and kidney, pelvic, and heart percentage (P = 0.04) and increased longissimus muscle area (P = 0.01). These data demonstrate that RAC supplementation for 42 d improves feed efficiency, increases the rate of DMI without altering DMI, and increases muscling in finishing cattle.

Systems Biology Reveals NR2F6 and TGFB1 as Key Regulators of Feed Efficiency in Beef Cattle

Systems biology approaches are used as strategy to uncover tissue-specific perturbations and regulatory genes related to complex phenotypes. We applied this approach to study feed efficiency (FE) in beef cattle, an important trait both economically and environmentally. Poly-A selected RNA of five tissues (adrenal gland, hypothalamus, liver, skeletal muscle and pituitary) of eighteen young bulls, selected for high and low FE, were sequenced (Illumina HiSeq 2500, 100 bp, pared-end). From the 17,354 expressed genes considering all tissues, 1,335 were prioritized by five selection categories (differentially expressed, harboring SNPs associated with FE, tissue-specific, secreted in plasma and key regulators) and used for network construction. NR2F6 and TGFB1 were identified and validated by motif discovery as key regulators of hepatic inflammatory response and muscle tissue development, respectively, two biological processes demonstrated to be associated with FE. Moreover, we indicated potential biomarkers of FE, which are related to hormonal control of metabolism and sexual maturity. By using robust methodologies and validation strategies, we confirmed the main biological processes related to FE in Bos indicus and indicated candidate genes as regulators or biomarkers of superior animals.

Growth performance and carcass traits of steers finished on three different systems including legume-grass pasture and grain diets

Inclusion of legume in grass pastures optimizes protein values of the forage and promotes improved digestibility. Therefore, we hypothesized that finishing steers on a novel combination of legumes and grass pasture would produce carcasses with acceptable traits when compared to carcasses from steers finished in feedlot systems. In this study, we evaluated the effects of finishing steers on three systems including: grazing legume-grass pasture containing oats, ryegrass, white and red clover (PAST), grazing PAST plus supplementation with whole corn grain (14 g/kg BW (SUPP)), and on a feedlot-confined system with concentrate only (28 g/kg BW, consisting of 850 g/kg of whole corn grain and 150 g/kg of protein-mineral-vitamin supplement (GRAIN)) on growth performance of steers, carcass traits and digestive disorders. Eighteen steers were randomly assigned to one of three dietary treatments and finished for 91 days. Data regarding pasture and growth performance were collected during three different periods (0 to 28, 29 to 56 and 57 to 91 days). Subsequently, steers were harvested to evaluate carcass traits, presence of rumenitis, abomasitis and liver abscesses. The legume-grass pasture provided more than 19% dry matter of protein. In addition, pasture of paddocks where steers were assigned to SUPP and PAST treatments showed similar nutritional quality. When compared to PAST, finishing on SUPP increased total weight gain per hectare, stocking rate, daily and total weight gains. The increase of weight gain was high to GRAIN than SUPP and PAST. Steers finished on GRAIN had high hot carcass weight, fat thickness and marbling score when compared to PAST. However, these attributes did not differ between GRAIN and SUPP. Abomasum lesions were more prevalent in steers finished on GRAIN when compared to PAST. Results of this research showed that it is possible to produce carcasses with desirable market weight and fat thickness by finishing steers on legume-grass pasture containing oats, ryegrass, white and red clover. Moreover, supplementing steers with corn when grazing on legume-grass pasture produced similar carcass traits when compared to beef fed corn only.

Influence of feeding direct-fed microbial supplementation on growth performance and feeding behavior in naturally fed and conventionally fed finishing cattle with different dietary adaptation periods

To determine the effects of finishing system (conventional vs. natural), dietary adaptation length (14 vs. 28 d), and direct-fed microbial (DFM) supplementation (no DFM vs. DFM) on growth performance and feeding behavior, 120 yearling steers (390 ± 2.8 kg) were used in a completely randomized design with a 2 × 2 × 2 factorial arrangement of treatments. Feed intake was monitored using the Insentec feeding system. Blood samples were collected every 28 d. After 140 d on feed, steers were slaughtered and carcass characteristics collected. Conventionally fed steers had greater (P ≤ 0.001) final BW, carcass weight, and dressing %. Dry matter intake was not influenced (P ≥ 0.31) by treatment. Length of dietary adaptation period did not influence (P ≥ 016) final BW, ADG, and G:F. There was a feeding system × DFM interaction (P ≤ 0.02) for ADG and G:F with conventionally fed steers fed DFM having the greatest (P ≤ 0.05) and naturally fed steers supplemented with DFM having the least (P ≤ 0.05) ADG and G:F. Number of visits to the feed bunk and number of meals per day did not differ (P > 0.05) among treatments. Time eating per visit and per meal was greater (P = 0.05) in steers supplemented with DFM than in steers not supplemented with DFM. On day 56 and 140, plasma glucose concentration was greater (P ≤ 0.03) in steers adapted in 14 d than in steers adapted in 28 d. On day 84, plasma glucose concentration was greater (P = 0.02) in naturally fed compared to conventionally fed steers. On day 112, there was a dietary adaptation period × DFM interaction (P = 0.004) for plasma glucose concentration with glucose concentration greatest (P ≤ 0.05) in steers adapted in 14 d supplemented with DFM and in steers adapted in 28 d not supplemented with DFM, least for steers adapted in 28 d supplemented with DFM, with steers adapted in 14 d not supplemented with DFM intermediate (P ≤ 0.05). On day 112 and 140, plasma urea N concentration was greater (P ≤ 0.05) in steers adapted in 28 d than in steers adapted in 14 d. These data indicate that conventionally fed steers generally had improved growth performance compared to naturally fed steers. Length of dietary adaptation and DFM supplementation had minimal effects on growth performance but did interact with feeding system to influence feeding behavior and blood metabolite concentrations.

Genome-wide association study identifies loci and candidate genes for internal organ weights in Simmental beef cattle

Cattle internal organs as accessible raw materials have a long history of being widely used in beef processing, feed and pharmaceutical industry. These traits not only are of economic interest to breeders, but they are intrinsically linked to many valuable traits, such as growth, health, and productivity. Using the Illumina Bovine HD 770K SNP array, we performed a genome-wide association study for heart weight, liver weight, spleen weight, lung weight, and kidney weight in 1,217 Simmental cattle. In our research, 38 significant single nucleotide polymorphisms (SNPs) ( P < 1.49 × 10−6) were identified for five internal organ weight traits. These SNPs are within or near 13 genes, and some of them have been reported previously, including NDUFAF4, LCORL, BT.94996, SLIT2, FAM184B, LAP3, BBS12, MECOM, CD300LF, HSD17B3, TLR4, MXI1, and MB21D2. In addition, we detected four haplotype blocks on BTA6 containing 18 significant SNPs associated with spleen weight. Our results offer worthy insights into understanding the genetic mechanisms of internal organs' development, with potential application in breeding programs of Simmental beef cattle.

Influence of limit-feeding and time of day of feed availability to growing calves on growth performance and feeding behavior in cold weather

Objective swere to determine the effects of limit-feeding and time of feed access in cold weather on growth performance and feeding behavior of growing calves fed a corn silage-based diet. Sixty-six steers (BW = 317 ± 5.3 kg) and 30 heifers (BW = 239 ± 7.6 kg) were assigned randomly to dietary treatment: 1) ad libitum feed intake (AL), 2) limit-fed to 80% of the average DMI of the AL group on a BW basis in the daytime (0601-1759 h; LF-D), 3) limit-fed to 80% of the average DMI of the AL group on a BW basis in the nighttime (1800-0559 h; LF-N), and 4) limit-fed to 80% of the average DMI of the AL group on a BW basis, split 1/2 in the daytime and 1/2 in the nighttime (LF-S). Feed intake and feeding behavior were monitored over 84 d using the Insentec feeding system. Average daily gain, DMI, and G:F were greater ( ≤ 0.002) in the AL group compared with others. Dry matter intake was not different ( = 0.17) when comparing the LF-D with the LF-N groups. Average daily gain and G:F were greater ( ≤ 0.05) when comparing the LF-N group to the LF-D group, and were not different ( ≥ 0.51) when comparing the LF-S group with the mean of the LF-D and LF-N groups. Number of visits and meals per d was greater ( ≤ 0.001) in the LF-N than the LF-D group. Feed intake per visit was not different ( = 0.55) when comparing the AL group and others, and tended to be greater ( = 0.06) in the LF-D than the LF-N group. Feed intake per meal was greater ( < 0.001) when comparing the AL group with others, and the LF-D with the LF-N group. Feed intake per minute (eating rate) was not influenced by treatment. In conclusion, limit-feeding at 80% of ad libitum intake decreased ADG and G:F. Limit-feeding in the nighttime as compared to limit-feeding in the daytime improves growth performance and increases feeding activity (number of visits and meals per d) which could be because of increased heat production to help maintain body temperature and thus reduce maintenance energy requirements.

Exploration of Biological Markers of Feed Efficiency in Young Bulls

The efficiency with which ruminants convert feed to desirable products is difficult to measure under normal commercial settings. We explored the use of potential biological markers from easily obtainable samples, that is, blood, hair, and feces, to characterize potential causes of divergent efficiency when considered as residual feed intake (RFI) or feed conversion efficiency (FCE). A total of 54 Charolais bulls, 20 in period 1 and 34 in period 2, were examined for individual dry matter intake (DMI) and growth. Bulls were offered a diet of 70:30 wrapped grass silage to concentrate for 99 d. At the conclusion of the test period, blood samples were collected for the determination of vitamins B₂ and B₆, and plasma used for the determination of metabolites, natural isotopic ¹⁵N abundance (¹⁵N NIA, expressed as δ¹⁵N ‰) and fractionation (Δ¹⁵N_{plasma proteins-diet} and Δ¹³C_{plasma proteins-diet}) and near-infrared spectroscopy (NIRS). Feces were analyzed by NIRS. Bulls were slaughtered at 15-17 months of age and carcass characteristics determined. Bulls were ranked according to RFI with extremes (SD ± 0.5; n = 31) classified as either efficient (Neg-RFI) or inefficient (Pos-RFI). Extreme bulls were then classified for FCE (high vs low FCE), changing the groups. Pos-RFI bulls consumed 14% more feed than Neg-RFI bulls for the same level of weight gain. Low FCE bulls tended to eat more, but had lower weight gains than high FCE bulls. No differences were detected in carcass conformation, fat scores, hot carcass weight, or dressing percentage. Yet, heart and bladder weights were heavier in Pos-RFI, and rumen weight tended to be heavier in Pos-RFI bulls. RFI did not affect bulk ¹⁵N or ¹³C fractionation. A negative correlation was observed between FCE and Δ¹⁵N_{plasma proteins-diet}. Inefficient bulls (Pos-RFI) had higher δ¹⁵N in glycine compared to Neg-RFI bulls. Similarly, metabolomic analysis showed a tendency for concentrations of glycine and sarcosine to be elevated in Pos-RFI bulls, whereas aspartic acid and carnosine tended to be elevated, and serine tended to be lower in High FCE. Among vitamins, only flavin adenine dinucleotide concentration was higher in the blood of bulls with High FCE. These results suggest that the two feed efficiency metrics differ in the underlying mechanisms of metabolism, where RFI is driven by differences in the energetic requirements of visceral organs and the extent of AA catabolism.

Influence of feeding increasing levels of dry or modified wet corn distillers grains plus solubles in whole corn grain-based finishing cattle diets on pancreatic α-amylase and trypsin activity

The objectives of this study were to determine the effect of dietary inclusion [0%–50% of diet dry matter (DM)] and form (dry and modified wet) of corn distillers grains plus solubles (DGS) on pancreatic α-amylase and trypsin activities in calves. Feeding up to 50% DGS did not negatively impact pancreatic exocrine function.

Partitioning of feed intake into maintenance and gain in growing beef cattle: Evaluation of conventional and Bayesian analyses

The robustness of efficiency estimates depends on theoretical consistency of models from which those estimates are developed; functional forms of the variables must be globally consistent with theoretical properties regarding feed utilization for maintenance and gain in growing and finishing cattle. Model parameter estimates and their dimensions must be unique or estimates of feed utilization and gain will not reflect reality. A linear equation commonly used to estimate daily DMI by the th individual animal (ADFI), based on mean weight and gain during a feeding period, was evaluated to determine if that model was correctly specified and if the vector predicted ADFI differed from the vector observed ADFI. Three independently gathered data sets were evaluated using a multiple linear regression model; variability described by that model failed to capture observed variability in the data (lack of fit, < 0.10), and predicted ADFI differed from observed ( < 0.05); for 1 of the 3 data sets, residuals were not normally distributed ( < 0.001). Functional forms of the variables in the first model evaluated, characterizing ADFI required for maintenance ( × BW) and gain ( × ADG), were consistent with neither published empirical nor theoretical relationships among ADFI, BW, and ADG. Parameter estimates determined for that linear model were not BLUE. Better fits among final BW, initial BW, and ADFI were found for a first-order relationship, in which final BW was a function of initial BW and ADFI, as indicated by > 0.90. The linear model and, to a lesser degree, the first nonlinear model lacked theoretical and global consistency. A second nonlinear model, which described retained energy as a function of ME intake, best fit the data, and functional forms of variables describing ME intake at maintenance and the efficiency of ME utilization for gain were consistent with theoretical estimates found in the literature. Changes in feed intake and live BW in linear and nonlinear models failed to adequately describe efficiencies of metabolic processes, which are better characterized by changes in retained energy as a function of ME intake in nonlinear models.

Profile of the Spleen Transcriptome in Beef Steers with Variation in Gain and Feed Intake

We have previously identified components of the immune system contributing to feed intake and gain in both the rumen and small intestine of beef steers. In this study, we examined the spleen, a major lymphatic organ near the digestive tract, to determine whether it was also influencing individual feed efficiency status through immune responses. Animals (n = 16) that were divergent for gain and intake were selected for tissue sampling. The spleen transcriptomes were evaluated by microarray. A total of 1216 genes were identified as differentially expressed. Genes were over-represented in Kyoto encyclopedia of genes and genomes (KEGG) pathways including biological regulation, protein folding, cell communication, immune systems process, response to stress, and RNA metabolic process. Several stress response or heat shock genes including HSPH1, HSPA1A, HSPA4, DNAJB4, DNAJA4, etc., were identified as a stress response functional gene cluster in the low gain-low intake animals. These genes were up-regulated amongst the low gain-low intake animals compared to all other groups. Canonical pathways associated with the differentially expressed genes included the coagulation system, extrinsic prothrombin activation, protein ubiquitination, unfolded protein response, and aldosterone signaling in epithelial cells. An analysis of expressed copy number variable (CNV) genes in the spleen produced some of the same genes and gene families that were differentially expressed. Our data suggests the splenic contribution to some of the underlying variation among gain and intake within this group of animals may be a result of immune function and stress response. In addition, some of the differences in immune response functions may be related to gene copy number.

Effects of realimentation after nutrient restriction during mid- to late gestation on pancreatic digestive enzymes, serum insulin and glucose levels, and insulin-containing cell cluster morphology

This study examined effects of stage of gestation and nutrient restriction with subsequent realimentation on maternal and foetal bovine pancreatic function. Dietary treatments were assigned on day 30 of pregnancy and included: control (CON; 100% requirements; n = 18) and restricted (R; 60% requirements; n = 30). On day 85, cows were slaughtered (CON, n = 6; R, n = 6), remained on control (CC; n = 12) and restricted (RR; n = 12), or realimented to control (RC; n = 11). On day 140, cows were slaughtered (CC, n = 6; RR, n = 6; RC, n = 5), remained on control (CCC, n = 6; RCC, n = 5) or realimented to control (RRC, n = 6). On day 254, the remaining cows were slaughtered and serum samples were collected from the maternal jugular vein and umbilical cord to determine insulin and glucose concentrations. Pancreases from cows and foetuses were removed, weighed, and subsampled for enzyme and histological analysis. As gestation progressed, maternal pancreatic α-amylase activity decreased and serum insulin concentrations increased (p ≤ 0.03). Foetal pancreatic trypsin activity increased (p < 0.001) with advancing gestation. Foetal pancreases subjected to realimentation (CCC vs. RCC and RRC) had increased protein and α-amylase activity at day 254 (p ≤ 0.02), while trypsin (U/g protein; p = 0.02) demonstrated the opposite effect. No treatment effects were observed for maternal or foetal pancreatic insulin-containing cell clusters. Foetal serum insulin and glucose levels were reduced with advancing gestation (p ≤ 0.03). The largest maternal insulin-containing cell cluster was not influenced by advancing gestation, while foetal clusters grew throughout (p = 0.01). These effects indicate that maternal digestive enzymes are influenced by nutrient restriction and there is a potential for programming of increased foetal digestive enzyme production resulting from previous maternal nutrient restriction.

Liver transcriptomic networks reveal main biological processes associated with feed efficiency in beef cattle

BACKGROUND

The selection of beef cattle for feed efficiency (FE) traits is very important not only for productive and economic efficiency but also for reduced environmental impact of livestock. Considering that FE is multifactorial and expensive to measure, the aim of this study was to identify biological functions and regulatory genes associated with this phenotype.

RESULTS

Eight genes were differentially expressed between high and low feed efficient animals (HFE and LFE, respectively). Co-expression analyses identified 34 gene modules of which 4 were strongly associated with FE traits. They were mainly enriched for inflammatory response or inflammation-related terms. We also identified 463 differentially co-expressed genes which were functionally enriched for immune response and lipid metabolism. A total of 8 key regulators of gene expression profiles affecting FE were found. The LFE animals had higher feed intake and increased subcutaneous and visceral fat deposition. In addition, LFE animals showed higher levels of serum cholesterol and liver injury biomarker GGT. Histopathology of the liver showed higher percentage of periportal inflammation with mononuclear infiltrate.

CONCLUSION

Liver transcriptomic network analysis coupled with other results demonstrated that LFE animals present altered lipid metabolism and increased hepatic periportal lesions associated with an inflammatory response composed mainly by mononuclear cells. We are now focusing to identify the causes of increased liver lesions in LFE animals.

Influence of feeding increasing levels of dry or modified wet corn distillers’ grains plus solubles in whole corn grain-based finishing diets on hepatic and renal mass, and glutathione peroxidase and urea cycle enzyme activities in finishing cattle

Salim, H., Wood, K. M., Cant, J. P. and Swanson, K. C. 2015. Influence of feeding increasing levels of dry or modified wet corn distillers’ grains plus solubles in whole corn grain-based finishing diets on hepatic and renal mass, and glutathione peroxidase and urea cycle enzyme activities in finishing cattle. Can. J. Anim. Sci. 95: 407–415. Forty-two cross-bred steers (BW=357±5.8 kg) fed whole corn grain-based finishing diets were used in a completely randomized block (60, 120, or 180 d on feed) design (2×3 factorial arrangement of treatments plus control) to determine the effect of inclusion level [0 (control), 16.7, 33.3, and 50% of diet DM) and form (dry (DDGS) or modified wet (MWDGS)] of distillers’ grains plus solubles (DGS) on hepatic and renal glutathione peroxidase (GPx) and hepatic urea cycle enzyme activities. Kidney weight (g kg−1of BW) increased linearly (P=0.004) with increasing inclusion levels of DGS. There were no effects (P≥0.11) of dietary treatment on hepatic and renal GPx activity (U g−1, U mg−1of protein, and kU liver−1). Hepatic carbamoyl phosphate synthetase activity (kU liver−1and U kg−1of BW) tended to linearly increase (P=0.09 and P=0.10, respectively) with increasing inclusion level of DGS. Hepatic ornithine transcarbamoylase and argininosuccinate synthetase activity (kU liver−1and U kg−1of BW) increased linearly (P≤0.05) with increasing inclusion levels of DGS. These data indicate that steers adapt to feeding up to 50% DGS by increasing kidney mass and activity of urea cycle enzymes in liver to allow for clearance of excess nitrogen. Also, hepatic and renal GPx activity, as an indicator of Se status, is not affected when typical finishing diets are fed.

Differences in transcript abundance of genes on BTA15 located within a region associated with gain in beef steers

Using results from a previous GWAS, we chose to evaluate seven genes located within a 229Kb region on BTA15 for variation in RNA transcript abundance in a library of tissue samples that included adipose, liver, rumen papillae, spleen, muscle, and small intestine epithelial layers from the duodenum, ileum and jejunum collected from steers (n = 14) with positive and negative residual GN near mean dry matter intake (DMI). The genes evaluated were two olfactory receptor-like genes (LOC525033 and LOC618173), RRM1, STIM1, RHOG, PGAP2, and NUP98. The rumen papillae transcript abundance of RHOG was positively correlated with residual GN (P = 0.02) and ruminal STIM1 exhibited a trend towards an association with residual GN (P = 0.08). The transcript abundance of one olfactory receptor (LOC618173) in the ileum was also positively associated with residual GN (P = 0.02) and PGAP2 and LOC525033 in the ileum displayed trends for association with GN (P ≤ 0.1). To further evaluate the differential expression detected in the ileum and rumen of these animals, the transcript abundance of STIM1 and RHOG in the rumen and of PGAP2 and the olfactory receptors in the ileum were assessed in an additional group of 32 animals with divergent average daily gain (ADG) and average daily feed intake (ADFI) collected over two groups. The olfactory receptor, LOC525033, was not expressed in the ileum for the majority of these animals. Only RHOG showed a slight, but non-significant trend towards greater expression in animals with greater gain. We have detected differences in the transcript abundance of genes within this region in the rumen and ileum of animals selected for greater and less residual gain; however, we were unable to validate the expression of these genes in the larger group of cattle possibly due to the differences in phenotype or contemporary group.

Small intestinal digestion of raw cornstarch in cattle consuming a soybean hull-based diet is improved by duodenal casein infusion

Six duodenally and ileally cannulated steers were used in 3 sequential studies to measure 1) basal nutrient flows from a soybean hull-based diet, 2) small intestinal digestibility of raw cornstarch continuously infused into the duodenum, and 3) responses of small intestinal starch digestion to duodenal infusion of 200 or 400 g/d casein. Our objective was to evaluate responses in small intestinal starch digestion in cattle over time and to measure responses in small intestinal starch digestion to increasing amounts of MP. On average, cattle consumed 3.7 kg/d DM, 68 g/d dietary N, and 70 g/d dietary starch. Starch flow to the duodenum was small (38 g/d), and N flow was 91 g/d. Small intestinal digestibility of duodenal N was 57%, and small intestinal digestion of duodenal starch flow was extensive (92%). Small intestinal starch digestibility was 34% when 1.5 kg/d raw cornstarch was continuously infused into the duodenum. Subsequently, cattle were placed in 1 of 2 replicated Latin squares that were balanced for carryover effects to determine response to casein infusions and time required for adaptation. Duodenal infusion of casein linearly increased (P ≤ 0.05) small intestinal starch digestibility, and small intestinal starch digestion adapted to infusion of casein in 6 d. Ethanol-soluble starch and unpolymerized glucose flowing to the ileum increased linearly (P ≤ 0.05) with increasing infusion of casein. Plasma cholecystokinin was not affected by casein infusion, but circulating levels of glucose were increased by casein supplementation (P ≤ 0.05). Responses in small intestinal starch digestion in cattle adapted to casein within 6 d, and increases in duodenal supply of casein up to 400 g/d increased small intestinal starch digestion in cattle.

Small intestinal growth measures are correlated with feed efficiency in market weight cattle, despite minimal effects of maternal nutrition during early to midgestation

We hypothesized that gestational nutrition would affect calf feed efficiency and small intestinal biology, which would be correlated with feed efficiency. Multiparous beef cows (n = 36) were individually fed 1 of 3 diets from d 45 to 185 of gestation: native grass hay and supplement to meet NRC recommendations (control [CON]), 70% of CON NEm (nutrient restricted [NR]), or a NR diet with a RUP supplement (NR+RUP) to provide similar essential AA as CON. After d 185 of gestation, cows were managed as a single group, and calf individual feed intake was measured with the GrowSafe System during finishing. At slaughter, the small intestine was dissected and sampled. Data were analyzed with calf sex as a block. There was no effect (P ≥ 0.33) of maternal treatment on residual feed intake, G:F, DMI, ADG, or final BW. Small intestinal mass did not differ (P ≥ 0.38) among treatments, although calf small intestinal length tended (P = 0.07) to be greater for NR than NR+RUP. There were no differences (P ≥ 0.20) in calf small intestinal density or jejunal cellularity, proliferation, or vascularity among treatments. Jejunal soluble guanylate cyclase mRNA was greater (P < 0.03) for NR+RUP than CON and NR. Residual feed intake was positively correlated (P ≤ 0.09) with small intestinal mass and relative mass and jejunal RNA content but was negatively correlated (P ≤ 0.09) with jejunal mucosal density and DNA concentration. Gain:feed was positively correlated (P ≤ 0.09) with jejunal mucosal density, DNA, protein, and total cells and was negatively correlated (P ≤ 0.05) with small intestinal relative mass, jejunal RNA, and RNA:DNA. Dry matter intake was positively correlated (P ≤ 0.09) with small intestinal mass, relative mass, length, and density as well as jejunal DNA and protein content, total cells, total vascularity, and kinase insert domain receptor and endothelial nitric oxide synthase 3 mRNA and was negatively correlated (P = 0.02) with relative small intestinal length. In this study, calf performance and efficiency during finishing as well as most measures of small intestinal growth were not affected by maternal nutrient restriction during early and midgestation. Results indicate that offspring small intestinal gene expression may be affected by gestational nutrition even when apparent tissue growth is unchanged. Furthermore, small intestinal size and growth may explain some variation in efficiency of nutrient utilization in feedlot cattle.

Influence of dry-rolled corn processing and increasing dried corn distillers grains plus solubles inclusion for finishing cattle on growth performance and feeding behavior

Sixty-four yearling steers (345 ± 4.2 kg BW) were used to study the effects of degree of dry-rolled corn processing and corn dried distillers grains plus solubles (DDGS) inclusion on feeding and ruminating behavior, G:F, and carcass characteristics. Steers were assigned randomly to 1 of 4 experimental treatments (n = 16 per treatment): 1) coarse-rolled (2.68 mm) corn and 20% DDGS, 2) coarse-rolled corn and 40% DDGS, 3) fine-rolled (1.46 mm) corn and 20% DDGS, and 4) fine-rolled corn and 40% DDGS. Final BW and ADG were not affected by corn processing or DDGS. Dry matter intake (kg/d and % of BW) decreased (P < 0.001) and G:F increased (P < 0.001) with increasing inclusion of DDGS. Meal number increased (P ≤ 0.05) and meal size decreased (P < 0.001) with finer dry-roll corn processing and with increasing inclusion of DDGS. Drinking time decreased (P = 0.03) with finer dry-rolled corn processing and tended to increase (P = 0.06) with increased inclusion of DDGS. Rumination time while standing decreased (P = 0.03) with increased inclusion of DDGS. Increasing inclusion of DDGS from 20 to 40% decreased intake, increased G:F, and altered feeding behavior of finishing steers consuming a 90% concentrate diet without affecting carcass quality. Increasing the degree of dry-roll corn processing did not impact growth performance and did not interact with increasing inclusion of DDGS in finishing diets.

Detecting novel SNPs and breed-specific haplotypes at calpastatin gene in Iranian fat- and thin-tailed sheep breeds and their effects on protein structure

Calpastatin has been introduced as a potential candidate gene for growth and meat quality traits. In this study, genetic variability was investigated in the exon 6 and its intron boundaries of ovine CAST gene by PCR-SSCP analysis and DNA sequencing. Also a protein sequence and structural analysis were performed to predict the possible impact of amino acid substitutions on physicochemical properties and structure of the CAST protein. A total of 487 animals belonging to four ancient Iranian sheep breeds with different fat metabolisms, Lori-Bakhtiari and Chall (fat-tailed), Zel-Atabay cross-bred (medium fat-tailed) and Zel (thin-tailed), were analyzed. Eight unique SSCP patterns, representing eight different sequences or haplotypes, CAST-1, CAST-2 and CAST-6 to CAST-11, were identified. Haplotypes CAST-1 and CAST-2 were most common with frequency of 0.365 and 0.295. The novel haplotype CAST-8 had considerable frequency in Iranian sheep breeds (0.129). All the consensus sequences showed 98-99%, 94-98%, 92-93% and 82-83% similarity to the published ovine, caprine, bovine and porcine CAST locus sequences, respectively. Sequence analysis revealed four SNPs in intron 5 (C24T, G62A, G65T and T69-) and three SNPs in exon 6 (c.197A>T, c.282G>T and c.296C>G). All three SNPs in exon 6 were missense mutations which would result in p.Gln 66 Leu, p.Glu 94 Asp and p.Pro 99 Arg substitutions, respectively, in CAST protein. All three amino acid substitutions affected the physicochemical properties of ovine CAST protein including hydrophobicity, amphiphilicity and net charge and subsequently might influence its structure and effect on the activity of Ca2+ channels; hence, they might regulate calpain activity and afterwards meat tenderness and growth rate. The Lori-Bakhtiari population showed the highest heterozygosity in the ovine CAST locus (0.802). Frequency difference of haplotypes CAST-10 and CAST-8 between Lori-Bakhtiari (fat-tailed) and Zel (thin-tailed) breeds was highly significant (P<0.001), indicating that these two haplotypes might be breed-specific haplotypes that distinguish between fat-tailed and thin-tailed sheep breeds.

Influence of supplementation with corn dried distillers grains plus solubles to growing calves fed medium-quality hay on growth performance and feeding behavior

To determine the effect of increasing supplementation of corn dried distillers grains plus solubles (DDGS) on growth performance and feeding behavior, 70 steer calves (287 ± 10 kg of BW) were blocked by BW to 3 pens equipped with Insentec feeders. For 84 d, calves were fed medium-quality grass/legume hay offered for ad libitum intake and provided 1 of 3 dietary supplemental treatments (n = 7 or 8 steers per treatment within each pen; n = 23 or 24 per treatment): 1) nothing, 2) DDGS at 0.5% of BW daily (DM basis), and 3) DDGS at 1% of BW daily (DM basis). Hay intake (kg/d and % of BW daily) decreased linearly (P < 0.001) as DDGS supplementation increased. Total DMI (kg/d and % of BW) increased linearly (P < 0.001) with DDGS supplementation. Average daily gain and gain efficiency (G:F) responded quadratically (P ≤ 0.006) as G:F increased to a lesser extent when DDGS supplementation increased from 0.5 to 1% than from 0 to 0.5%. Meals (number per day) and time eating per meal for hay and total diet decreased linearly (P ≤ 0.006) with increasing DDGS supplementation. Time eating per day for hay responded quadratically (P < 0.001) and decreased to a greater extent when increasing from 0 to 0.5% DDGS supplementation than from 0.5 to 1% DDGS. Feed intake per minute (eating rate) for hay and total diet increased linearly (P ≤ 0.05) with increasing DDGS supplementation. On d 84, LM area, back fat thickness, and rump fat thickness increased linearly (P ≤ 0.006) with increasing DDGS supplementation. There were significant day × treatment interactions (P < 0.001) for plasma glucose and urea-N concentrations. Glucose did not change over the feeding period in control steers but increased in both supplemented groups. Urea-N decreased for control steers over the feeding period whereas urea-N increased in supplemented steers. In conclusion, supplementation of DDGS in amounts of 0.5 or 1% of BW daily can be used to reduce hay intake and improve ADG and G:F in growing steers fed medium-quality hay. Additionally, DDGS supplementation alters feeding behavior.

Effect of moderate dietary restriction on visceral organ weight, hepatic oxygen consumption, and metabolic proteins associated with energy balance in mature pregnant beef cows

Twenty-two nonlactating multiparous pregnant beef cows (639 ± 68 kg) were used to investigate the effect of dietary restriction on the abundance of selected proteins regulating cellular energy metabolism. Cows were fed at either 85% (n = 11; LOW) or 140% (n = 11; HIGH) of total NE requirements. The diet consisted of a haylage-based total mixed ration containing 20% wheat straw. Cows were slaughtered by block (predicted date of parturition), beginning 83 d after the initiation of dietary treatments and every week thereafter for 6 wk, such that each block was slaughtered at approximately 250 d of gestation. Tissue samples from liver, kidney, sternomandibularis muscle, ruminal papilli (ventral sac), pancreas, and small intestinal muscosa were collected at slaughter and snap frozen in liquid N2. Western blots were conducted to quantify abundance of proliferating cell nuclear antigen (PCNA), ATP synthase, ubiquitin, and Na/K+ ATPase for all tissues; PPARγ, PPARγ coactivator 1 α (PGC-1α), and 5´-adenosine monophosphate-activated protein kinase (AMPK) and the activated form phosphorylated-AMPK (pAMPK) for liver, muscle, and rumen; phosphoenolpyruvate carboxykinase (PEPCK) for liver and kidney; and uncoupling protein 2 (UCP2) for liver. Statistical analysis was conducted using Proc Mixed in SAS and included the fixed effects of dietary treatment, cow age, block, and the random effect of pen. Dietary treatments resulted in cows fed HIGH having greater (P ≤ 0.04) ADG and final BW than cows fed LOW. Abundance of ubiquitin in muscle was greater (P = 0.009) in cows fed LOW, and PCG-1 α in liver was greater (P = 0.03) in cows fed HIGH. Hepatic O2 consumption was greater in HIGH (P ≤ 0.04). Feed intake can influence the abundance of important metabolic proteins and suggest that protein degradation may increase in muscle from moderately nutrient restricted cows and that energy metabolism in liver increases in cows fed above NE requirements.

Genome-wide association analyses for growth and feed efficiency traits in beef cattle

A genome-wide association study using the Illumina 50K BeadChip included 38,745 SNP on 29 BTA analyzed on 751 animals, including 33 purebreds and 718 crossbred cattle. Genotypes and 6 production traits: birth weight (BWT), weaning weight (WWT), ADG, DMI, midtest metabolic BW (MMWT), and residual feed intake (RFI), were used to estimate effects of individual SNP on the traits. At the genome-wide level false discovery rate (FDR < 10%), 41 and 5 SNP were found significantly associated with BWT and WWT, respectively. Thirty-three of them were located on BTA6. At a less stringent significance level (P < 0.001), 277 and 27 SNP were in association with single traits and multiple traits, respectively. Seventy-three SNP on BTA6 and were mostly associated with BW-related traits, and heavily located around 30 to 50Mb. Markers that significantly affected multiple traits appeared to impact them in same direction. In terms of the size of SNP effect, the significant SNP (P < 0.001) explained between 0.26 and 8.06% of the phenotypic variation in the traits. Pairs of traits with low genetic correlation, such as ADG vs. RFI or DMI vs. BWT, appeared to be controlled by 2 groups of SNP; 1 of them affected the traits in same direction, the other worked in opposite direction. This study provides useful information to further assist the identification of chromosome regions and subsequently genes affecting growth and feed efficiency traits in beef cattle.

The relationship between feed efficiency traits and fertility in young beef bulls

Awda, B. J., Miller, S. P., Montanholi, Y. R., Vander Voort, G., Caldwell, T., Buhr, M. M. and Swanson, K. C. 2013. The relationship between feed efficiency traits and fertility in young beef bulls. Can. J. Anim. Sci. 93: 185–192. Great efforts have been taken in recent years for improving feed efficiency in beef cattle. Despite there being several studies on biological factors associated with this trait, little is known about the potential relationships between fertility and feed efficiency in beef cattle. The objective of this study was to examine the relationship between feed efficiency traits and bull fertility traits [sperm motility, viability and scrotal circumference (SC)]. From a total of 328 crossbred beef bulls that were subjected to a performance test (112 d in each of 6 yr), SC was measured and semen collected from 110 bulls using the electroejaculation method (average age±SE=417±2.5 d). Sperm were extended, cooled, and frozen in liquid nitrogen. Two residual feed intake (RFI) measures were considered with different prediction models for dry matter intake (DMI), RFIKoch included size and growth rate and RFIbkft included the additional adjustment for backfat thickness (BKFT). Sperm viability, motility and progressive motility of the 10 bulls with the greatest RFIKoch (Hi-RFIKoch) were greater than those of the 10 bulls with the lowest RFIKoch (Lo-RFIKoch; P<0.05, 0.01, and 0.05, respectively). Sperm motility (P<0.01), progressive motility and SC (P<0.05) of the 10 bulls with the greatest RFIbkft (Hi-RFIbkft) were greater than those of the 10 bulls with the lowest RFIbkft (Lo-RFIbkft). In summary, these data indicate that young beef bulls with greater feed efficiency have decreased sperm motility, sperm viability and SC, which is an undesirable effect of selection for improved feed efficiency that needs to be addressed through multiple trait selection.

Greenhouse gas emissions from beef cattle pen surfaces in North Dakota

There is a global interest to quantify and mitigate greenhouse gas (GHG) (e.g. methane-CH4, nitrous oxide-N2O and carbon dioxide-CO2) emissions in animal feeding operations. The goal of this study was to quantify GHG emissions from the feedlot pen surface under North Dakota climatic conditions. In this study gaseous flux from the pen surfaces was generated using a custom-made wind tunnel at different times of the year (summer, fall, winter and spring). Gaseous fluxes (air samples) were drawn in the Tedlar bags using a vacuum chamber and gas concentrations were measured using a gas chromatograph within 24 h of sampling. The CH4 concentrations and flux rates (FRs) or flux among the months were not significantly different. Overall CH4, CO2 and N2O concentrations over a 7-month period were 2.66, 452 and 0.67 ppm, respectively. Estimated overall CH4, CO and N2O FRs were 1.32, 602 and 0.90 g m(-2) d(-1), respectively. Estimated emission rates using the wind tunnel were 38 g hd(-1) d(-1), 17 kg hd(-1) d(-1) and 26 g hd(-1) d(-1) for CH4, CO2 and N2O, respectively. The emission factors for GHG estimated in the research for North Dakota climate were the first of its kind, and these emission estimates can be used as a basis for planning and implementing management practices to minimize GHG emissions.

Influence of sire breed on the interplay among rumen microbial populations inhabiting the rumen liquid of the progeny in beef cattle

This study aimed to evaluate whether the host genetic background impact the ruminal microbial communities of the progeny of sires from three different breeds under different diets. Eighty five bacterial and twenty eight methanogen phylotypes from 49 individuals of diverging sire breed (Angus, ANG; Charolais, CHA; and Hybrid, HYB), fed high energy density (HE) and low energy density (LE) diets were determined and correlated with breed, rumen fermentation and phenotypic variables, using multivariate statistical approaches. When bacterial phylotypes were compared between diets, ANG offspring showed the lowest number of diet-associated phylotypes, whereas CHA and HYB progenies had seventeen and twenty-three diet-associated phylotypes, respectively. For the methanogen phylotypes, there were no sire breed-associated phylotypes; however, seven phylotypes were significantly different among breeds on either diet (P<0.05). Sire breed did not influence the metabolic variables measured when high energy diet was fed. A correlation matrix of all pairwise comparisons among frequencies of bacterial and methanogen phylotypes uncovered their relationships with sire breed. A cluster containing methanogen phylotypes M16 (Methanobrevibacter gottschalkii) and M20 (Methanobrevibacter smithii), and bacterial phylotype B62 (Robinsoniella sp.) in Angus offspring fed low energy diet reflected the metabolic interactions among microbial consortia. The clustering of the phylotype frequencies from the three breeds indicated that phylotypes detected in CHA and HYB progenies are more similar among them, compared to ANG animals. Our results revealed that the frequency of particular microbial phylotypes in the progeny of cattle may be influenced by the sire breed when different diets are fed and ultimately further impact host metabolic functions, such as feed efficiency.

A proteomics approach to detect tissue-wide adaptive changes in the pancreas associated with increased pancreatic α-amylase activity in domestic cattle (Bos taurus)

We used a proteomics-based approach to investigate potential regulatory proteins in the pancreas of domestic cattle (Bos taurus) that were associated with differences in pancreatic α-amylase activity. Two groups of 48 and 45 crossbred steers in years 1 and 2, respectively, were fed a high moisture corn-based diet and were ranked according to their pancreatic α-amylase activity. Steers (n=18) with high, medium, and low α-amylase activity were selected, with 3 for each activity range and 9 for each experimental year, and their proteomic profiles were compared. Pancreatic samples from each animal were fractionated using 2D-HPLC and fractions detected using UV spectrophotometry. Software analysis revealed 119 common protein fractions among the 18 animals, and statistical analysis revealed 10 of these fractions differing (P<0.10) in abundance between animals from the high and low pancreatic α-amylase activity groups. Five protein fractions identified after tandem mass spectrometry analysis and database searches were found to match proteins with protein-binding, nucleotide/DNA-binding or enzymatic capabilities. Bioinformatics analysis of these fractions revealed porphobilinogen deaminase, a DNA-binding protein, and a putative S1 peptidase that increased in abundance with increasing α-amylase activity; with a putative ATP/GTP binding protein decreasing in abundance with increasing pancreatic α-amylase activity. Changes in these fractions may represent adaptations of the pancreas in domestic cattle that are associated with differences in α-amylase activity.

Grazed grass herbage intake and performance of beef heifers with predetermined phenotypic residual feed intake classification

Data were collected on 85 Simmental and Simmental × Holstein-Friesian heifers. During the indoor winter period, they were offered grass silage ad libitum and 2 kg of concentrate daily, and individual dry matter intake (DMI) and growth was recorded over 84 days. Individual grass herbage DMI was determined at pasture over a 6-day period, using the n-alkane technique. Body condition score, skeletal measurements, ultrasonic fat and muscle depth, visual muscularity score, total tract digestibility, blood hormones, metabolites and haematology variables and activity behaviour were measured for all heifers. Phenotypic residual feed intake (RFI) was calculated for each animal as the difference between actual DMI and expected DMI during the indoor winter period. Expected DMI was calculated for each animal by regressing average daily DMI on mid-test live weight (LW)(0.75) and average daily gain (ADG) over an 84-day period. Standard deviations above and below the mean were used to group animals into high (>0.5 s.d.), medium (±0.5 s.d.) and low (<0.5 s.d.) RFI. Overall mean (s.d.) values for DMI (kg/day), ADG (kg), feed conversion ratio (FCR) kg DMI/kg ADG and RFI (kg dry matter/day) were 5.82 (0.73), 0.53 (0.18), 12.24 (4.60), 0.00 (0.43), respectively, during the RFI measurement period. Mean DMI (kg/day) and ADG (kg) during the grazing season was 9.77 (1.77) and 0.77 (0.14), respectively. The RFI groups did not differ (P > 0.05) in LW, ADG or FCR at any stage of measurement. RFI was positively correlated (r = 0.59; P < 0.001) with DMI during the RFI measurement period but not with grazed grass herbage DMI (r = 0.06; P = 0.57). Low RFI heifers had 0.07 greater (P < 0.05) concentration of plasma creatinine than high RFI heifers and, during the grazed herbage intake period, spent less time standing and more time lying (P < 0.05) than high RFI heifers. However, low and high RFI groups did not differ (P > 0.05) in ultrasonic backfat thickness or muscle depth, visual muscle scores, skeletal size, total tract digestibility or blood hormone and haematology variables at any stage of the experiment. Despite a sizeable difference in intake of grass silage between low and high RFI heifers during the indoor winter period, there were no detectable differences between RFI groupings for any economically important performance traits measured when animals were offered ensiled or grazed grass herbage.