Ruminal transcript abundance of the centromere-associated protein E gene may influence residual feed intake in beef steers.

A better understanding regarding the mechanisms by which the rumen processes feed may assist us in identifying animals with superior feed efficiency. Studies to evaluate the gene expression of rumen tissue have previously been performed to analyze their relationship with feed efficiency. Continuing this research is critical to determine whether the expression of the genes identified is associated with feed efficiency in additional populations of beef cattle to ensure that they are robust across breed and environment. A previous rumen-transcriptome study on Hereford × Angus steers identified 122 differentially expressed genes (PFDR  < 0.05) associated with residual feed intake (RFI), a measure of feed efficiency. The purpose of our study was to test the most divergent, up- and down-regulated genes in the rumen tissue of an unrelated population of Hereford × Angus steers that included two contemporary groups. A total of 13 genes were evaluated by quantitative real-time PCR. The centromere-associated protein E (CENPE) gene was expressed in lower concentrations in the rumen epithelium of steers in the more efficient (low RFI) group in both contemporary groups of animals, which was the same as the previous study. In addition, CENPE, a gene involved in chromosome alignment during mitosis, has also been associated with growth traits in cattle and pigs. There was no relationship between the expression of the other 12 genes tested with RFI in the population of steers in this study, which illustrates the importance of validating gene expression data in additional populations.

Dynamics of genomic architecture during composite breed development in cattle.

Some livestock breeds face the challenge of reduced genetic variation, increased inbreeding depression owing to genetic drift and selection. Hybridization can reverse these processes and increase levels of productivity and adaptation to various environmental stressors. Samples from American Brangus were used to evaluate the indicine/taurine composition through nine generations (~45 years) after the hybridization process was completed. The purpose was to determine how hybridization alters allelic combinations of a breed over time when genetic factors such as selection and drift are operating. Furthermore, we explored genomic regions with deviations from the expected composition from the progenitor breeds and related these regions to traits under selection. The Brangus composition deviated from the theoretical expectation, defined by the breed association, of 62.5% taurine, showing taurine composition to be 70.4 ± 0.6%. Taurine and indicine proportion were not consistent across chromosomes. Furthermore, these non-uniform areas were found to be associated with traits that were probably under selection such as intermuscular fat and average daily gain. Interestingly, the sex chromosomes were predominantly taurine, which could be due to the composite being formed particularly in the final cross that resulted in progeny designated as purebred Brangus. This work demonstrated the process of new breed formation on a genomic level. It suggests that factors like genetic drift, selection and complementarity shift the genetic architecture into a uniquely different population. These findings are important to better understand how hybridization and crossbreeding systems shape the genetic architecture of composite populations.

Validation of SNP associations with bovine ovulation and twinning rate.

Previous work identified SNP associations with twinning rate in the US Holstein population and developed a model for genomic prediction. The current study was conducted to assess the association of these SNPs with twinning rate and ovulation rate in a genetically diverse, outbred population selected for twinning and ovulation rate. A total of 18 SNPs that were components of a prediction equation for twinning rate in Holstein cattle were genotyped on 731 animals from the USDA Meat Animal Research Center production efficiency or twinning population. These 731 individuals were sires and dams well represented in the pedigrees of animals from the twinner population, and their genotypes were used in predicting genotypes for animals in the larger population (n = 16 035). Twinning rate and ovulation rate were analyzed in a two-trait repeated records analysis with marker associations analyzed individually as fixed effects. Criteria for marker validation were effect estimate with a sign consistent with previous estimates and significance at a nominal P < 0.01. Of the 14 SNPs passing quality control assessments, only one was validated. A SNP in the 5' flanking region of the IGF1 gene, discovered previously in a positional candidate gene analysis, was significantly associated with twinning rate in the USDA twinning population (P < 0.0002). This SNP may have utility in genomic prediction of twinning rate beyond the Holstein population.

The impact of the bovine faecal microbiome on Escherichia coli O157:H7 prevalence and enumeration in naturally infected cattle.

AIMS: The objective of this study was to determine if the faecal microbiome has an association with Escherichia coli O157:H7 prevalence and enumeration. METHODS AND RESULTS: Pyrosequencing analysis of faecal microbiome was performed from feedlot cattle fed one of three diets: (i) 94 heifers fed low concentrate (LC) diet, (ii) 142 steers fed moderate concentrate (MC) diet, and (iii) 132 steers fed high concentrate (HC) diet. A total of 322 585 OTUs were calculated from 2,411,122 high-quality sequences obtained from 368 faecal samples. In the LC diet group, OTUs assigned to the orders Clostridiales and RF39 (placed within the class Mollicutes) were positively correlated with both E. coli O157:H7 prevalence and enumeration. In the MC diet group, OTUs assigned to Prevotella copri were positively correlated with both E. coli O157:H7 prevalence and enumeration, whereas OTUs assigned to Prevotella stercorea were negatively correlated with both E. coli O157:H7 prevalence and enumeration. In both the MC diet group and the HC diet group, OTUs assigned to taxa placed within Clostridiales were both positively and negatively correlated with both E. coli O157:H7 prevalence and enumeration. However, all correlations were weak. In both the MC diet group and the HC diet group, stepwise linear regression through backward elimination analyses indicated that these OTUs were significantly correlated (P < 0·001) with prevalence or enumeration, explaining as much as 50% of variability in E. coli O157:H7 prevalence or enumeration. CONCLUSIONS: Individual colonic bacterial species have little impact on E. coli O157:H7 shedding but collectively groups of bacteria were strongly associated with pathogen shedding. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacterial groups in the bovine colon may impact faecal shedding of the zoonotic pathogen E. coli O157:H7, and manipulation of the intestinal microbiota to alter these bacteria may reduce shedding of this pathogen and foodborne illnesses.

Linkage disequilibrium among commonly genotyped SNP variants detected from bull sequence.

Genomic prediction utilizing causal variants could increase selection accuracy above that achieved with SNPs genotyped by currently available arrays used for genomic selection. A number of variants detected from sequencing influential sires are likely to be causal, but noticeable improvements in prediction accuracy using imputed sequence variant genotypes have not been reported. Improvement in accuracy of predicted breeding values may be limited by the accuracy of imputed sequence variants. Using genotypes of SNPs on a high-density array and non-synonymous SNPs detected in sequence from influential sires of a multibreed population, results of this examination suggest that linkage disequilibrium between non-synonymous and array SNPs may be insufficient for accurate imputation from the array to sequence. In contrast to 75% of array SNPs being strongly correlated to another SNP on the array, less than 25% of the non-synonymous SNPs were strongly correlated to an array SNP. When correlations between non-synonymous and array SNPs were strong, distances between the SNPs were greater than separation that might be expected based on linkage disequilibrium decay. Consistently near-perfect whole-genome linkage disequilibrium between the full array and each non-synonymous SNP within the sequenced bulls suggests that whole-genome approaches to infer sequence variants might be more accurate than imputation based on local haplotypes. Opportunity for strong linkage disequilibrium between sequence and array SNPs may be limited by discrepancies in allele frequency distributions, so investigating alternate genotyping approaches and panels providing greater chances of frequency-matched SNPs strongly correlated to sequence variants is also warranted. Genotypes used for this study are available from https://www.animalgenome.org/repository/pub/;USDA2017.0519/.

Relationships between the genes expressed in the mesenteric adipose tissue of beef cattle and feed intake and gain.

Mesenteric fat, a depot within the visceral fat, accumulates in cattle during maturation and finishing and may be a potential source of production inefficiency. The aim of this study was to determine whether the genes expressed in the mesenteric fat of steers were associated with body weight gain and feed intake. Sixteen steers chosen by their rank of distance from the bivariate mean for gain and feed intake were used for this study. Mesenteric fat was obtained and evaluated for differences in gene expression. A total of 1831 genes were identified as differentially expressed among steers with variation in feed intake and gain. Many of these genes were involved with metabolic processes such as proteolysis, transcription and translation. In addition, the Gene Ontology annotations including transport and localization were both over-represented among the differentially expressed genes. Pathway analysis was also performed on the differentially expressed genes. The superoxide radical degradation pathway was identified as over-represented based on the differential expression of the genes GPX7, SOD2 and TYRP1, suggesting a potential role for oxidative stress or inflammatory pathways among low gain-high intake animals. GPX7 and SOD2 were in lower transcript abundance, and TYRP1 was higher in transcript abundance among the low gain-high feed intake animals. The retinoate biosynthesis pathway was also enriched due to the differential expression of the genes AKR1C3, ALDH8A1, RDH8, RDH13 and SDR9C7. These genes were all more highly expressed in the low gain-high intake animals. The glycerol degradation and granzyme A signaling pathways were both associated with gain. Three glycerol kinase genes and the GZMA gene were differentially expressed among high vs. low gain animals. Mesenteric fat is a metabolically active tissue, and in this study, genes involved in proteolysis, transcription, translation, transport immune function, glycerol degradation and oxidative stress were differentially expressed among beef steers with variation in body weight gain and feed intake.

Ruminal expression of the NQO1, RGS5, and ACAT1 genes may be indicators of feed efficiency in beef steers.

Ruminal genes differentially expressed in crossbred beef steers from USMARC with variation in gain and feed intake were identified in a previous study. Several of the genes identified with expression patterns differing between animals with high gain-low feed intake and low gain-high feed intake were evaluated in a separate, unrelated population of Angus × Hereford beef steers from the University of Wyoming that was classified to differ in residual feed intake (RFI). Of the 17 genes tested, two were differentially expressed by RFI class in the Angus × Hereford animals. These genes included NAD(P)H dehydrogenase, quinone 1 (NQO1; P = 0.0009) and regulator of G-protein signaling 5 (RGS5; P = 0.01). A third gene, acetyl-CoA acetyltransferase 1 (ACAT1; P = 0.06), displayed a trend toward association with RFI. These data suggest that some of the genes identified in a previous rumen transcriptome discovery study may have utility for identifying or selecting for animals with superior feed efficiency phenotypes across cattle breeds and populations.

Differential gene expression in the duodenum, jejunum and ileum among crossbred beef steers with divergent gain and feed intake phenotypes.

Small intestine mass and cellularity were previously associated with cattle feed efficiency. The small intestine is responsible for the digestion of nutrients and absorption of fatty acids, amino acids and carbohydrates, and it contributes to the overall feed efficiency of cattle. The objective of this study was to evaluate transcriptome differences among the small intestine from cattle with divergent gain and feed intake. Animals most divergent from the bivariate mean in each of the four phenotypic Cartesian quadrants for gain × intake were selected, and the transcriptomes of duodenum, jejunum and ileum were evaluated. Gene expression analyses were performed comparing high gain vs. low gain animals, high intake vs. low intake animals and each of the phenotypic quadrants to all other groups. Genes differentially expressed within the high gain-low intake and low gain-high intake groups of animals included those involved in immune function and inflammation in all small intestine sections. The high gain-high intake group differed from the high gain-low intake group by immune response genes in all sections of the small intestine. In all sections of small intestine, animals with low gain-low intake displayed greater abundance of heat-shock genes compared to other groups. Several over-represented pathways were identified. These include the antigen-processing/presentation pathway in high gain animals and PPAR signaling, starch/sucrose metabolism, retinol metabolism and melatonin degradation pathways in the high intake animals. Genes with functions in immune response, inflammation, stress response, influenza pathogenesis and melatonin degradation pathways may have a relationship with gain and intake in beef steers.

Estimating heritability of wool shedding in a cross-bred ewe population.

Low wool prices and high production costs in sheep systems have resulted in the introduction of genotypes that shed wool into flocks to reduce shearing costs. Wool shedding occurs naturally in a few breeds and can be incorporated by cross-breeding. The opportunity to enhance shedding through selection depends on the extent of genetic variability present. Genetic and environmental parameters for wool shedding for ewes from a three-breed composite population were estimated using Bayesian inference. Data on 2025 cross-bred ewes, including 3345 wool shedding scores (WS) and 1647 breeding weight (BW) records, were analysed using bivariate and, for WS, univariate animal repeatability models. Breeding weight was included to account for possible selection bias. Breeding weight was moderately heritable and highly repeatable with means of 0.317 and 0.724, respectively. Under both models, WS was found to be moderately heritable and repeatable with means of 0.256 and 0.399, respectively. Based on a cumulative link model and contingency table analysis, age and reproductive activity influenced the extent of WS (p < 0.05). Given that WS is moderately heritable, selective gain in WS can be achieved.

Genetic markers that influence feed efficiency phenotypes also affect cattle temperament as measured by flight speed.

Flight speed is a predictive indicator of cattle temperament and is associated with feed efficiency phenotypes. Genetic markers associated with both traits may assist with selection of calmer animals with improved economic value. A preliminary genome-wide association study determined chromosomal regions on BTA9, and 17 were associated with flight speed. The genes quaking (QKI), glutamate receptor, ionotropic, AMPA 2 (GRIA2) and glycine receptor ß (GLRB) were identified in these regions as potential functional candidates. Beef steers (n = 1057) were genotyped with SNPs located within and flanking these genes. One SNP located near QKI and one near GRIA2 were nominally associated with flight speed (P ≤ 0.05) although neither was significant after Bonferroni correction. Several studies have shown a correlation between flight speed and feed intake or gain; therefore, we also analyzed SNPs on BTA6:38-39 Mb known to be associated with average daily gain (ADG) and average daily feed intake (ADFI) for association with flight speed. Several SNPs on BTA6 were associated with flight speed (P ≤ 0.005), and three were significant after Bonferroni correction. These results suggest that the genes tested are unlikely to contribute to flight speed variation for our cattle population, but SNPs on BTA6 associated with ADG and ADFI may influence temperament. Use of these markers to select for economically important feed efficiency phenotypes may produce cattle with more desirable temperaments.

DNA polymorphisms and transcript abundance of PRKAG2 and phosphorylated AMP-activated protein kinase in the rumen are associated with gain and feed intake in beef steers.

Beef steers with variation in feed efficiency phenotypes were evaluated previously on a high-density SNP panel. Ten markers from rs110125325-rs41652818 on bovine chromosome 4 were associated with average daily gain (ADG). To identify the gene(s) in this 1.2-Mb region responsible for variation in ADG, genotyping with 157 additional markers was performed. Several markers (n = 41) were nominally associated with ADG, and three of these, including the only marker to withstand Bonferroni correction, were located within the protein kinase, AMP-activated, gamma 2 non-catalytic subunit (PRKAG2) gene. An additional population of cross-bred steers (n = 406) was genotyped for validation. One marker located within the PRKAG2 loci approached a significant association with gain. To evaluate PRKAG2 for differences in transcript abundance, we measured expression in the liver, muscle, rumen and intestine from steers (n = 32) with extreme feed efficiency phenotypes collected over two seasons. No differences in PRKAG2 transcript abundance were detected in small intestine, liver or muscle. Correlation between gene expression level of PRKAG2 in rumen and average daily feed intake (ADFI) was detected in both seasons (P < 0.05); however, the direction differed by season. Lastly, we evaluated AMP-activated protein kinase (AMPK), of which PRKAG2 is a subunit, for differences among ADG and ADFI and found that the phosphorylated form of AMPK was associated with ADFI in the rumen. These data suggest that PRKAG2 and its mature protein, AMPK, are involved in feed efficiency traits in beef steers. This is the first evidence to suggest that rumen AMPK may be contributing to ADFI in cattle.

A region on BTA14 that includes the positional candidate genes LYPLA1, XKR4 and TMEM68 is associated with feed intake and growth phenotypes in cattle(1).

Feed cost for beef cattle is the largest expense incurred by cattle producers. The development of genetic markers to enhance selection of more efficient animals that require less feed while still achieving acceptable levels of production has the potential to substantially reduce production costs. A genome-wide marker association approach based on the Illumina BovineSNP50 BeadChip™ was used to identify genomic regions affecting average daily feed intake (ADFI), average daily gain (ADG) and residual feed intake traits in a population of 1159 crossbred steers. This approach identified a region on BTA14 from 22.02 to 23.92 Mb containing several single-nucleotide polymorphisms (SNPs) that have significant association with at least one of the traits. Two genes in this region, lysophospholipase 1 (LYPLA1) and transmembrane protein 68 (TMEM68), appeared to be logical positional and functional candidate genes. LYPLA1 deacylates ghrelin, a hormone involved in the regulation of appetite in the rat stomach, while TMEM68 is expressed in bovine rumen, abomasum, intestine and adipose tissue in cattle, and likely affects lipid biosynthetic processes. SNPs lying in or near these two genes were identified by sequencing a subset of animals with extreme phenotypes. A total of 55 SNPs were genotyped and tested for association with the same population of steers. After correction for multiple testing, five markers within 22.79-22.84 Mb, located downstream of TMEM68, and between TMEM68 and the neighbouring gene XKR4, were significant for both ADFI and ADG. Genetic markers predictive of feed intake and weight gain phenotypes in this population of cattle may be useful for the identification and selection of animals that consume less feed, although further evaluation of these markers for effects on other production traits and validation in additional populations will be required.

Genetic markers on BTA14 predictive for residual feed intake in beef steers and their effects on carcass and meat quality traits.

With the high cost of feed for animal production, genetic selection for animals that metabolize feed more efficiently could result in substantial cost savings for cattle producers. The purpose of this study was to identify DNA markers predictive for differences among cattle for traits associated with feed efficiency. Crossbred steers were fed a high-corn diet for 140 days and average daily feed intake (ADFI), average daily gain (ADG), and residual feed intake (RFI) phenotypes were obtained. A region on chromosome 14 was previously associated with RFI in this population of animals. To develop markers with the highest utility for predicting an animal's genetic potential for RFI, we genotyped additional markers within this chromosomal region. These polymorphisms were genotyped on the same animals (n = 1066) and tested for association with ADFI, ADG and RFI. Six markers within this region were associated with RFI (P ≤ 0.05). After conservative correction for multiple testing, one marker at 25.09 Mb remained significant (P = 0.02) and is responsible for 3.6% of the RFI phenotypic variation in this population of animals. Several of these markers were also significant for ADG, although none were significant after correction. Marker alleles with positive effects on ADG corresponded to lower RFI, suggesting an effect increasing growth without increasing feed intake. All markers were also assessed for their effects on meat quality and carcass traits. All of the markers associated with RFI were associated with adjusted fat thickness (AFT, P ≤ 0.009) and three were also associated with hot carcass weight (HCW, P ≤ 0.003). Marker alleles associated with lower RFI were also associated with reduced AFT, and if they were associated for HCW, the effect was an increase in weight. These markers may be useful as prediction tools for animals that utilize feed more efficiently; however, validation with additional populations of cattle is required.

Genetic variation in the mannosidase 2B2 gene and its association with ovulation rate in pigs.

Ovulation rate is an important phenotypic trait that is a critical component of litter size in pigs. Despite being moderately heritable in pigs, selection for increased ovulation rate is difficult because it is difficult to measure and is a sex-limited trait. A QTL for ovulation rate residing on the p-terminal end of pig chromosome 8 has been detected in a Meishan-cross resource population. Comparative analysis of this region yielded a positional candidate gene, mannosidase 2B2 (MAN2B2), for this QTL. The entire coding region of MAN2B2 was resequenced in the Meishan and White Composite founder animals of the resource population to identify SNPs. Eleven polymorphisms that alter the protein product of MAN2B2 were discovered and tested for statistical associations with ovulation rate in three generations of the resource population. The polymorphism located at position 1574 of the mRNA (D28521:c.1574A>G) was the most significant polymorphism tested (P = 0.00005) where the additive effect of the c.1574A allele was estimated to be -0.89 ova. This polymorphism was determined to be more significantly associated with ovulation rate than the breed-specific analysis conducted during the line-cross QTL discovery. The c.1574A>G marker was not associated with ovulation rate in an occidental population. Therefore, either MAN2B2 has a unique epistatic interaction within the Meishan-cross population or the c.1574A>G SNP is in linkage disequilibrium with the actual causative genetic variation in the Meishan-cross population.

Opportunities for collaborative phenotyping for disease resistance traits in a large beef cattle resource population.

The Germplasm Evaluation (GPE) Project at the US Meat Animal Research Center (USMARC) is planned to produce about 3,000 calves per year in support of the following objectives: identification and validation of genetic polymorphisms related to economically relevant traits (ERT), estimation of breed and heterosis effects among 16 breeds for ERT, and estimation of genetic correlations among ERT and physiological indicator traits (PIT). Opportunities exist for collaboration in the development and collection of PIT phenotypes for disease resistance. Other areas of potential collaboration include detailed diagnosis (identification of disease causing organisms, etc.) of treated animals, collaborative development of epidemiological statistical models that would extract more information from the records of diagnoses and treatments, or pharmacogenetics. Concentrating a variety of different phenotypes and research approaches on the same population makes each component much more valuable than it would be individually.

Association of preweaning and weaning serum cortisol and metabolites with ADG and incidence of respiratory disease in beef cattle.

The objectives of this experiment were to determine the association of circulating cortisol, lactate, and glucose at, and prior to, weaning with ADG and incidences of bovine respiratory disease (BRD) in beef cattle. A blood sample was collected approximately 3 wk prior to weaning and at weaning from genetically diverse steers and heifers ( = 451). Cattle were weighed periodically throughout the study and ADG was calculated for the preweaning period (152 ± 15 d), the receiving period (45 d postweaning), the finishing period (200 d), and total postweaning ADG. Incidences of BRD were recorded and analyzed as a binary trait. Lung lesions were recorded at slaughter. Preweaning serum cortisol concentrations were positively associated ( = 0.040) with receiving ADG and explained 0.74% of the variance of receiving ADG. Preweaning glucose concentrations were positively associated ( < 0.001) with preweaning ADG and negatively associated with receiving ( = 0.003), finishing ( = 0.008), and total postweaning ADG ( = 0.002) and explained 2.0% of the variance in total postweaning ADG. Variation in preweaning serum glucose concentrations could be indicative of variation in milk consumption, and therefore indicate calves receiving less milk grow slower prior to weaning, but experience compensatory gain postweaning. Cattle that were diagnosed with BRD ( = 130) grew slower during the receiving phase ( = 0.004), but total postweaning ADG was not different from cattle not diagnosed with BRD ( = 0.683). Additionally, cattle that were diagnosed with BRD in the feedlot tended ( = 0.062) to have slightly lower preweaning serum glucose concentrations. Using a logistic regression analysis, none of the serum variables measured at or before weaning were predictive of developing BRD ( > 0.180). Weaning serum glucose concentrations tended to be predictive of the presence of lung lesions at weaning ( = 0.060). These data indicate that glucose measured early in life is associated with growth rate, and could indicate that carbohydrate metabolism could contribute to variation in ADG.

Analysis of the gut bacterial communities in beef cattle and their association with feed intake, growth, and efficiency.

The impetus behind the global food security challenge is direct, with the necessity to feed almost 10 billion people by 2050. Developing a food-secure world, where people have access to a safe and sustainable food supply, is the principal goal of this challenge. To achieve this end, beef production enterprises must develop methods to produce more pounds of animal protein with less. Selection for feed-efficient beef cattle using genetic improvement technologies has helped to understand and improve the stayability and longevity of such traits within the herd. Yet genetic contributions to feed efficiency have been difficult to identify, and differing genetics, feed regimens, and environments among studies contribute to great variation and interpretation of results. With increasing evidence that hosts and their microbiomes interact in complex associations and networks, examining the gut microbial population variation in feed efficiency may lead to partially clarifying the considerable variation in the efficiency of feed utilization. The use of metagenomics and high-throughput sequencing has greatly impacted the study of the ruminant gut. The ability to interrogate these systems at great depth has permitted a greater understanding of the microbiological and molecular mechanisms involved in ruminant nutrition and health. Although the microbial communities of the reticulorumen have been well documented to date, our understanding of the populations within the gastrointestinal tract as a whole is limited. The composition and phylogenetic diversity of the gut microbial community are critical to the overall well-being of the host and must be determined to fully understand the relationship between the microbiomes within segments of the cattle gastrointestinal tract and feed efficiency, ADG, and ADFI. This review addresses recent research regarding the bacterial communities along the gastrointestinal tract of beef cattle; their association with ADG, ADFI, and feed efficiency; and the potential implications for beef production.

Differential expression of genes related to gain and intake in the liver of beef cattle.

BACKGROUND: To better understand which genes play a role in cattle feed intake and gain, we evaluated differential expression of genes related to gain and intake in the liver of crossbred beef steers. Based on past transcriptomics studies on cattle liver, we hypothesized that genes related to metabolism regulation and the inflammatory response would be differentially expressed. This study used 16 animals with diverse gain and intake phenotypes to compare transcript abundance after a 78 day ad libitum feed study. RESULTS: A total of 729 genes were differentially expressed. These genes were analyzed for over-representation among biological and cellular functions, and pathways. Cell transport processes and metabolic processes, as well as functions related to transport, were identified. Pathways related to immune function, such as the proteasome ubiquitination pathway and the chemokine signaling pathway, were also identified. CONCLUSIONS: Our results were consistent with past transcriptomics studies that have found immune and transport processes play a role in feed efficiency. Gain and intake are impacted by complex processes in the liver, which include cellular transport, metabolism regulation, and immune function.

Endocannabinoid concentrations in plasma during the finishing period are associated with feed efficiency and carcass composition of beef cattle.

We previously have shown that plasma concentrations of endocannabinoids (EC) are positively correlated with feed efficiency and leaner carcasses in finishing steers. However, whether the animal growth during the finishing period affects the concentration of EC is unknown. The objective of this study was to quantify anandamide (AEA) and 2-arachidonyl glycerol (2-AG) in plasma during different stages of the finishing period and identify possible associations with production traits and carcass composition in beef calves. Individual DMI and BW gain were measured on 236 calves ( = 127 steers and = 109 heifers) for 84 d on a finishing ration. Blood samples were collected on d 0 (early), 42 (mid), and 83 (late) of days on study (DOS). Cattle were slaughtered 44 d after the feeding study. Plasma concentration of AEA at 0 DOS was indirectly associated with the G:F ( < 0.01) and directly associated with residual feed intake (RFI; < 0.05) in steers. In contrast, plasma concentration of AEA at 83 DOS was directly associated with the G:F and indirectly associated RFI in heifers and steers ( < 0.01). In addition, AEA concentration at 42 and 83 DOS was positively associated with ADG and DMI ( < 0.01) in heifers and steers. Furthermore, 2-AG concentration at 42 DOS was positively associated with ADG in steers ( < 0.01) and heifers ( < 0.10). Plasma concentration of AEA was positively associated ( < 0.05) with HCW, USDA-calculated yield grade, and 12th-rib fat thickness in heifers, whereas no associations were found in steers. In contrast, 2-AG concentration was not associated with any carcass traits. These results provide evidence that circulating EC change during animal growth and that AEA concentration may be a useful predictor of growth and feed efficiency and, in females, of carcass attributes.