Association between fecal methanogen species with methane production and grazed forage intake of beef heifers classified for residual feed intake under drylot conditions.

Reduction in greenhouse gas emission from beef production is essential to the survival of the beef industry from environmental and social-economic perspectives. There are different systems available to measure methane from animals, but they are expensive, not easily accessible, and not suitable for large-scale methane measurements on the farm. Therefore exploring indicator traits, which are easy to measure, cost-effective, and suitable for large-scale measurement, are recommended. The objectives of this study were to examine the diversity of fecal methanogen profile among efficient and inefficient beef heifers on pasture and investigate methanogen profile as a possible proxy to predict methane emission in beef cattle consuming a forage diet. Forty pregnant (1st trimester) heifers previously classified for postweaning residual feed intake adjusted for off-test back fat (RFIfat; 20 high and 20 low) were included in this study. To determine individual pasture grazing intake, heifers were dosed with 1 kg of C32 labeled pellets once per day from Day 0 to Day 12, and fecal samples were collected twice daily from Day 8 to Day 15. Fecal samples from Days 8, 10, and 12 were analyzed for their methanogen profile. Animals were monitored individually for methane and carbon dioxide production using a GreenFeed Emissions Monitoring system. Total methanogen population and methanogenic community diversity of fecal samples were not different (P > 0.1) between low and high RFIfat groups, as measured by quantitative PCR and α- and ß-diversity indices. However, both groups had a different methanogen profile; the relative abundance of Methanobrevibacter wolinii and relatives were higher (P < 0.002), while that of Methanosphaera species ISO3-F5 was lower (P < 0.01) in low RFIfat cattle compared to the high RFIfat group. We also demonstrated that fecal methanogen profiles may be a useful proxy in predicting daily methane and carbon dioxide emissions with an adjusted R2 of 0.53 and 0.33, respectively, for low RFIfat heifers and 0.46 and 0.57, respectively, for the high RFIfat group.

Relationship between residual feed intake and radiated heat loss using infrared thermography in young beef bulls.

Residual feed intake (RFI) has been used to select metabolically efficient cattle in beef breeding programs, particularly for sire selection. Adoption of genetic selection using RFI has been limited due to the cost and difficulty of measuring individual feed intake. An alternative method of predicting RFI is to measure radiated heat loss using infrared thermography (IRT) as previous studies have shown promise using this technique to predict metabolic efficiency in mature cows, heifers, and growing bulls. The objective of this study was to explore use of IRT to predict RFI in growing beef bulls. Sixty bulls in each of two years were fed either a forage-based or a grain-based ration. Eye (Ey) and cheek (Ck) surface temperatures were measured using infrared images of the head collected on 16 and 14 sample days in Years 1 and 2, respectively, using a FLIR S60 camera. In Year 2, infrared images were collected continuously using a within-pen FLIR A310 camera system. Bulls were grouped into low, medium and high classes based on ±â€¯0.5 standard deviations of backfat adjusted residual feed intake (RFIFat); RFIFat values ranged from - 2.27 to + 2.61 kg DM day-1 (mean=0.0; SD=0.61). Sample day Ey and Ck temperatures were pooled and an average temperature was calculated for individual bulls. Average Ey and Ck temperatures measured using the FLIR S60 and the within-pen camera did not differ significantly across low, medium and high RFI groups (P > 0.05). Temperature deviations associated with extremes in ambient temperature (placing animals outside their thermoneutral zone) or underlying subclinical health problems could bias results in IRT measurements and RFI ranking. Standardization of IRT data and the conditions during measurement is necessary to more accurately assess its potential use to predict RFI.

Energy utilization in cattle with steady state and non-steady state methods: the importance of thermal neutrality.

The efficiency by which animals utilize dietary energy is fundamental to the cost of production for protein of animal origin and to the carbon footprint an animal industry has. Hence, the development of cost effective methodology for determining these measurements of efficiency is important. The objective of the present study was to investigate the use of infrared thermography in a rapid, non-steady state method for measuring energy loss in cattle. Data from 241 yearling bulls and steers as well as heifers and mature cows are presented. Infrared images were collected following a 24h feed withdrawal period. The infrared thermal response in these animals was significantly ranked (P < 0.03) with conventional measurements of feed efficiency using residual feed intake values for animals demonstrated to be within a thermal neutral zone. When animals were not within a thermal neutral zone there was no significant ranking. The data suggests that the use of a non-steady state approach using infrared thermography for identifying metabolic efficiency in animals may be a more rapid and less expensive method for identifying differences in energy utilization. The data also demonstrates the importance of maintaining thermal neutrality when measuring metabolic efficiency irrespective of the methodology.

Development and validation of a small SNP panel for feed efficiency in beef cattle.

The objective of this study was to develop and validate a customized cost-effective single nucleotide polymorphism (SNP) panel for genetic improvement of feed efficiency in beef cattle. The SNPs identified in previous association studies and through extensive analysis of candidate genomic regions and genes, were screened for their functional impact and allele frequency in Angus and Hereford breeds used as validation candidates for the panel. Association analyses were performed on genotypes of 159 SNPs from new samples of Angus (n = 160), Hereford (n = 329), and Angus-Hereford crossbred (n = 382) cattle using allele substitution and genotypic models in ASReml. Genomic heritabilities were estimated for feed efficiency traits using the full set of SNPs, SNPs associated with at least one of the traits (at P ≤ 0.05 and P < 0.10), as well as the Illumina bovine 50K representing a widely used commercial genotyping panel. A total of 63 SNPs within 43 genes showed association (P ≤ 0.05) with at least one trait. The minor alleles of SNPs located in the GHR and CAST genes were associated with decreasing effects on residual feed intake (RFI) and/or RFI adjusted for backfat (RFIf), whereas minor alleles of SNPs within MKI67 gene were associated with increasing effects on RFI and RFIf. Additionally, the minor allele of rs137400016 SNP within CNTFR was associated with increasing average daily gain (ADG). The SNPs genotypes within UMPS, SMARCAL, CCSER1, and LMCD1 genes showed significant over-dominance effects whereas other SNPs located in SMARCAL1, ANXA2, CACNA1G, and PHYHIPL genes showed additive effects on RFI and RFIf. Gene enrichment analysis indicated that gland development, as well as ion and cation transport are important physiological mechanisms contributing to variation in feed efficiency traits. The study revealed the effect of the Jak-STAT signaling pathway on feed efficiency through the CNTFR, OSMR, and GHR genes. Genomic heritability using the 63 significant (P ≤ 0.05) SNPs was 0.09, 0.09, 0.13, 0.05, 0.05, and 0.07 for ADG, dry matter intake, midpoint metabolic weight, RFI, RFIf, and backfat, respectively. These SNPs contributed to genetic variation in the studied traits and thus can potentially be used or tested to generate cost-effective molecular breeding values for feed efficiency in beef cattle.

Enteric methane emissions from low- and high-residual feed intake beef heifers measured using GreenFeed and respiration chamber techniques.

The objectives of this study were to evaluate the relationship between residual feed intake (RFI; g/d) and enteric methane (CH) production (g/kg DM) and to compare CH and carbon dioxide (CO) emissions measured using respiration chambers (RC) and the GreenFeed emission monitoring (GEM) system (C-Lock Inc., Rapid City, SD). A total of 98 crossbred replacement heifers were group housed in 2 pens and fed barley silage ad libitum and their individual feed intakes were recorded by 16 automated feeding bunks (GrowSafe, Airdrie, AB, Canada) for a period of 72 d to determine their phenotypic RFI. Heifers were ranked on the basis of phenotypic RFI, and 16 heifers (8 with low RFI and 8 with high RFI) were randomly selected for enteric CH and CO emissions measurement. Enteric CH and CO emissions of individual animals were measured over two 25-d periods using RC (2 d/period) and GEM systems (all days when not in chambers). During gas measurements metabolic BW tended to be greater ( ≤ 0.09) for high-RFI heifers but ADG tended ( = 0.09) to be greater for low-RFI heifers. As expected, high-RFI heifers consumed 6.9% more feed ( = 0.03) compared to their more efficient counterparts (7.1 vs. 6.6 kg DM/d). Average CH emissions were 202 and 222 g/d ( = 0.02) with the GEM system and 156 and 164 g/d ( = 0.40) with RC for the low- and high-RFI heifers, respectively. When adjusted for feed intake, CH yield (g/kg DMI) was similar for high- and low-RFI heifers (GEM: 27.7 and 28.5, = 0.25; RC: 26.5 and 26.5, = 0.99). However, CH yield differed between the 2 measurement techniques only for the high-RFI group ( = 0.01). Estimates of CO yield (g/kg DMI) also differed between the 2 techniques ( ≤ 0.03). Our study found that high- and low-efficiency cattle produce similar CH yield but different daily CH emissions. The 2 measurement techniques differ in estimating CH and CO emissions, partially because of differences in conditions (lower feed intakes of cattle while in chambers, fewer days measured in chambers) during measurement. We conclude that when intake of animals is known, the GEM system offers a robust and accurate means of estimating CH emissions from animals under field conditions.

Phenotypic and genetic relationships of residual feed intake measures and their component traits with fatty acid composition in subcutaneous adipose of beef cattle.

Feed efficiency is of particular interest to the beef industry because feed is the largest variable cost in production and fatty acid composition is emerging as an important trait, both economically and socially, due to the potential implications of dietary fatty acids on human health. Quantifying correlations between feed efficiency and fatty acid composition will contribute to construction of optimal multiple-trait selection indexes to maximize beef production profitability. In the present study, we estimated phenotypic and genetic correlations of feed efficiency measures including residual feed intake (RFI), RFI adjusted for final ultrasound backfat thickness (RFIf); their component traits ADG, DMI, and metabolic BW; and final ultrasound backfat thickness measured at the end of feedlot test with 25 major fatty acids in the subcutaneous adipose tissues of 1,366 finishing steers and heifers using bivariate animal models. The phenotypic correlations of RFI and RFIf with the 25 individual and grouped fatty acid traits were generally low (<0.25 in magnitude). However, relatively stronger genetic correlation coefficients of RFI and RFIf with PUFA traits including the -6:-3 ratio (0.52 ± 0.29 and 0.45 ± 0.31, respectively), 18:2-6 (0.45 ± 0.18 and 0.40 ± 0.19, respectively), -6 (0.43 ± 0.18 and 0.38 ± 0.19, respectively), PUFA (0.42 ± 0.18 and 0.36 ± 0.20, respectively), and 9-16:1 (-0.43 ± 0.20 and -0.33 ± 0.22, respectively) were observed. Hence, selection for low-RFI or more efficient beef cattle will improve fatty acid profiles by lowering the content of -6 PUFA, thus reducing the ratio of -6 to -3 along with increasing the amount of 9-16:1. Moderate to moderately high genetic correlations were also observed for DMI with 9-14:1 (-0.32 ± 0.17) and the sum of CLA analyzed (SumCLA; -0.45 ± 0.21), suggesting that selection of beef cattle with lower DMI will lead to an increase amount of 9-14:1 and SumCLA in the subcutaneous adipose tissue. However, unfavorable genetic correlations were detected for ADG with 11-18:1 (-0.38 ± 0.23) and SumCLA (-0.73 ± 0.26), implying that selection of beef cattle with a better growth rate will decrease the contents of healthy fatty acids 11-18:1 and SumCLA. Therefore, it is recommended that a multiple-trait selection index be used when genetic improvements of fatty acid composition, feed efficiency, feed intake, and growth are important in the breeding objective.

Application of fecal near-infrared reflectance spectroscopy profiling for the prediction of diet nutritional characteristics and voluntary intake in beef cattle.

The objective of this study was to evaluate the use of fecal near-infrared reflectance spectroscopy (NIRS) profiling to predict diet nutritional characteristics and voluntary DMI in beef cattle. Fecal samples were collected for growing cattle across 11 experiments in which individual animal performance and DMI was measured. Dried and ground fecal composite samples collected from each animal were subjected to fecal NIRS analysis by a Foss NIRS 6500 scanning monochromator (Foss, Eden Prairie, MN) at the Grazingland Animal Nutrition Laboratory (Temple, TX). Fecal spectra were then used to develop equations to predict diet composition (trials 1 to 11; = 408), digestibility (trials 1 to 5; = 155), and DMI (trials 1 to 11; = 408). Coefficients of determination for calibration () and cross-validation () for prediction of diet nutritional characteristics were lower for NDF ( = 0.85; = 0.82) than for CP ( = 0.90; = 0.88). For the prediction of DMI, and ranged from 0.69 and 0.67 for the prediction of trial-average DMI to 0.76 and 0.73 for the prediction of fecal-collection-period DMI. While the and obtained for the prediction of DMI were lower than those obtained for the prediction of diet composition or digestibility, fecal NIRS prediction equations for DMI were successful in predicting the mean DMI of groups, as no differences were found for the prediction of fecal-collection-period DMI (Diff. = 1.10; = 0.72) or trial DMI (Diff. = -0.47; = 0.86).

Phenotypic and genetic correlations of fatty acid composition in subcutaneous adipose tissue with carcass merit and meat tenderness traits in Canadian beef cattle.

Bivariate animal models were used to estimate phenotypic and genetic correlations between 9 carcass merit and meat tenderness traits with 25 individual and grouped fatty acids in the subcutaneous adipose tissue of a population of 1,366 Canadian beef cattle finishing heifers and steers. In general, phenotypic correlations were low (<0.25 in magnitude) except for moderate phenotypic correlations of 9-17:1 (-0.29 ± 0.16), 18:0 (0.26 ± 0.14), 11-18:1 (-0.33 ± 0.15), 11-18:1 (0.35 ± 0.14) with Warner-Bratzler shear force measured 3 d postmortem and between 14:0 (-0.36 ± 0.1), 9-14:1 (-0.34 ± 0.08), 9-16:1 (-0.36 ± 0.08), 9-18:1 (0.26 ± 0.07), and sum of branched-chain fatty acids (BCFA; -0.27 ± 0.06) and back fat thickness (BFAT). Genetic correlations were also low for most of the traits. However, moderate to moderately high genetic correlations (0.25 to 0.50 in magnitude) were detected for some traits, including 17:0 (0.4 ± 0.11), 18:0 (0.44 ± 0.12), 9-14:1 (-0.47 ± 0.11), 9-16:1 (-0.43 ± 0.11), and the -6:-3 PUFA ratio (-0.5 ± 0.15) with HCW; 9-14:1 (-0.41 ± 0.13) and 9-16:1 (-0.42 ± 0.13) with BFAT; 17:0 (0.43 ± 0.19) and BCFA (0.45 ± 0.19) with lean meat yield; 13-18:1 (0.40 ± 0.15) with carcass marbling score; sum of CLA (0.45 ± 0.22), 18:2-6 (0.47 ± 0.17), and sum of PUFA (0.48 ± 0.17) with overall tenderness measured 3 d postmortem; the -6:-3 PUFA ratio (0.41 ± 0.22) and sum of CLA (0.42 ± 0.25) with overall tenderness measured 29 d postmortem; and BCFA (0.41 ± 0.27) with Warner-Bratzler shear force measured 29 d postmortem. The genetic correlations observed in this study suggest that contents of some fatty acids in beef tissue and carcass merit and meat tenderness traits are likely influenced by a subset of the same genes in beef cattle. Due to some antagonistic genetic correlations, multiple-trait economic indexes are recommended when fatty acid composition, carcass merit, and meat tenderness traits are included in the breeding objective.

Relationship between phenotype, carcass characteristics and the incidence of dark cutting in heifers.

Previous research has suggested that cattle predisposed to dark cutting can be identified from live animal or carcass characteristics. This hypothesis was tested using production and phenotype data from an existing data set collected from heifers (n=467) on study at three farms. Carcasses in the data set graded Canada AAA (n=136), AA (n=296), A (n=14), and B4 (dark cutting, n=21). Farm was identified as significant (P=0.0268) by CATMOD analysis and slaughter weight and carcass weight accounted for the variation in dark cutting frequency across the farms. Analysis of variance indicated that dark cutting heifers had reduced weight at weaning (P<0.0001) and at slaughter (P<0.0001), and produced reduced weight carcasses (P<0.0001). Results of logistic regression indicated that the probability of dark cutting was decreased in heifers slaughtered at live weight greater than 550kg and in carcasses weighing greater than 325kg.

Accuracy of genomic predictions for feed efficiency traits of beef cattle using 50K and imputed HD genotypes.

The accuracy of genomic predictions can be used to assess the utility of dense marker genotypes for genetic improvement of beef efficiency traits. This study was designed to test the impact of genomic distance between training and validation populations, training population size, statistical methods, and density of genetic markers on prediction accuracy for feed efficiency traits in multibreed and crossbred beef cattle. A total of 6,794 beef cattle data collated from various projects and research herds across Canada were used. Illumina BovineSNP50 (50K) and imputed Axiom Genome-Wide BOS 1 Array (HD) genotypes were available for all animals. The traits studied were DMI, ADG, and residual feed intake (RFI). Four validation groups of 150 animals each, including Angus (AN), Charolais (CH), Angus-Hereford crosses (ANHH), and a Charolais-based composite (TX) were created by considering the genomic distance between pairs of individuals in the validation groups. Each validation group had 7 corresponding training groups of increasing sizes ( = 1,000, 1,999, 2,999, 3,999, 4,999, 5,998, and 6,644), which also represent increasing average genomic distance between pairs of individuals in the training and validations groups. Prediction of genomic estimated breeding values (GEBV) was performed using genomic best linear unbiased prediction (GBLUP) and Bayesian method C (BayesC). The accuracy of genomic predictions was defined as the Pearson's correlation between adjusted phenotype and GEBV (), unless otherwise stated. Using 50K genotypes, the highest average achieved in purebreds (AN, CH) was 0.41 for DMI, 0.34 for ADG, and 0.35 for RFI, whereas in crossbreds (ANHH, TX) it was 0.38 for DMI, 0.21 for ADG, and 0.25 for RFI. Similarly, when imputed HD genotypes were applied in purebreds (AN, CH), the highest average was 0.14 for DMI, 0.15 for ADG, and 0.14 for RFI, whereas in crossbreds (ANHH, TX) it was 0.38 for DMI, 0.22 for ADG, and 0.24 for RFI. The of GBLUP predictions were greatly reduced with increasing genomic average distance compared to those from BayesC predictions. The results indicate that 50K genotypes, used with BayesC, are more effective for predicting GEBV in purebred cattle. Imputed HD genotypes found utility when dealing with composites and crossbreds. Formulation of a fairly large training set for genomic predictions in beef cattle should consider the genomic distance between the training and target populations.

Genetic and phenotypic correlations among feed efficiency, production and selected conformation traits in dairy cows.

The difficulties and costs of measuring individual feed intake in dairy cattle are the primary factors limiting the genetic study of feed intake and utilisation, and hence the potential of their subsequent industry-wide applications. However, indirect selection based on heritable, easily measurable, and genetically correlated traits, such as conformation traits, may be an alternative approach to improve feed efficiency. The aim of this study was to estimate genetic and phenotypic correlations among feed intake, production, and feed efficiency traits (particularly residual feed intake; RFI) with routinely recorded conformation traits. A total of 496 repeated records from 260 Holstein dairy cows in different lactations (260, 159 and 77 from first, second and third lactation, respectively) were considered in this study. Individual daily feed intake and monthly BW and body condition scores of these animals were recorded from 5 to 305 days in milk within each lactation from June 2007 to July 2013. Milk yield and composition data of all animals within each lactation were retrieved, and the first lactation conformation traits for primiparous animals were extracted from databases. Individual RFI over 301 days was estimated using linear regression of total 301 days actual energy intake on a total of 301 days estimated traits of metabolic BW, milk production energy requirement, and empty BW change. Pair-wise bivariate animal models were used to estimate genetic and phenotypic parameters among the studied traits. Estimated heritabilities of total intake and production traits ranged from 0.27±0.07 for lactation actual energy intake to 0.45±0.08 for average body condition score over 301 days of the lactation period. RFI showed a moderate heritability estimate (0.20±0.03) and non-significant phenotypic and genetic correlations with lactation 3.5 % fat-corrected milk and average BW over lactation. Among the conformation traits, dairy strength, stature, rear attachment width, chest width and pin width had significant (P<0.05) moderate to strong genetic correlations with RFI. Combinations of these conformation traits could be used as RFI indicators in the dairy genetic improvement programmes to increase the accuracy of the genetic evaluation of feed intake and utilisation included in the index.

Transcriptomic analysis by RNA sequencing reveals that hepatic interferon-induced genes may be associated with feed efficiency in beef heifers.

In beef cattle, production feedstuffs are the largest variable input cost. Beef cattle also have a large carbon footprint, raising concern about their environmental impact. Unfortunately, only a small proportion of dietary energy is directed toward protein deposition and muscle growth whereas the majority supports body maintenance. Improving feed efficiency would, therefore, have important consequences on productivity, profitability, and sustainability of the beef industry. Various measures of feed efficiency have been proposed to improve feed utilization, and currently, residual feed intake (RFI) is gaining popularity. However, the cost associated with measuring RFI and the limited knowledge of the biology underlying improved feed efficiency make its adoption prohibitive. Identifying molecular mechanisms explaining divergence in RFI in beef cattle would lead to the development of early detection methods for the selection of more efficient breeding stock. The objective of this study was to identify hepatic markers of metabolic feed efficiency in replacement beef heifers. A group of 87 heifers were tested for RFI adjusted for off-test backfat thickness (RFIfat). Preprandial liver biopsies were collected from 10 high- and 10 low-RFIfat heifers (7 Hereford­Aberdeen Angus and 3 Charolais­Red Angus­Main Anjou per group) and gene expression analysis was performed using RNA sequencing and quantitative real-time PCR. The heifers used in this study differed in RFIfat averaging 0.438 vs. ­0.584 kg DM/d in high- and low-RFIfat groups, respectively. As expected, DMI was correlated with RFIfat and ADG did not differ between high- and low-RFIfat heifers. Through a combination of whole transcriptome and candidate gene analyses, we identified differentially expressed genes involved in inflammatory processes including hemoglobin ß (HBB), myxovirus resistance 1 interferon-inducible protein p78 (MX1), ISG15 ubiquitin-like modifier (ISG15), hect domain and RLD 6 (HERC6), and interferon-induced protein 44 (IFI44) whose mRNA abundance was lower (HBB) or higher (MX1, ISG15, HERC6, and IFI44) in low-RFIfat heifers. These genes have been shown to be directly or indirectly modulated by interferon signaling and involved with innate immunity. Our results suggest that more efficient heifers respond differently to hepatic proinflammatory stimulus, potentially expending less energy toward combating systemic inflammation and redirecting nutrients toward growth and protein accretion.

Modification of mature non-reducible collagen cross-link concentrations in bovine m. gluteus medius and semitendinosus with steer age at slaughter, breed cross and growth promotants.

Increased meat toughness with animal age has been attributed to mature trivalent collagen cross-link formation. Intramuscular trivalent collagen cross-link content may be decreased by reducing animal age at slaughter and/or inducing muscle re-modeling with growth promotants. This hypothesis was tested in m. gluteus medius (GM) and m. semitendinosus (ST) from 112 beef steers finished at either 12 to 13 (rapid growth) or 18 to 20 (slow growth) months of age. Hereford-Aberdeen Angus (HAA) or Charolais-Red Angus (CRA) steers were randomly assigned to receive implants (IMP), ractopamine (RAC), both IMP and RAC, or none (control). RAC decreased pyridinoline (mol/mol collagen) and IMP increased Ehrlich chromogen (EC) (mol/mol collagen) in the GM. In the ST, RAC increased EC (mol/mol collagen) but decreased EC (nmol/g raw muscle) in slow growing CRA steers. Also, IMP increased ST pyridinoline (nmol/g raw muscle) of slow-growing HAA steers. Results indicated alteration of perimysium collagen cross-links content in muscle in response to growth promotants.

Animal board invited review: genetic possibilities to reduce enteric methane emissions from ruminants.

Measuring and mitigating methane (CH4) emissions from livestock is of increasing importance for the environment and for policy making. Potentially, the most sustainable way of reducing enteric CH4 emission from ruminants is through the estimation of genomic breeding values to facilitate genetic selection. There is potential for adopting genetic selection and in the future genomic selection, for reduced CH4 emissions from ruminants. From this review it has been observed that both CH4 emissions and production (g/day) are a heritable and repeatable trait. CH4 emissions are strongly related to feed intake both in the short term (minutes to several hours) and over the medium term (days). When measured over the medium term, CH4 yield (MY, g CH4/kg dry matter intake) is a heritable and repeatable trait albeit with less genetic variation than for CH4 emissions. CH4 emissions of individual animals are moderately repeatable across diets, and across feeding levels, when measured in respiration chambers. Repeatability is lower when short term measurements are used, possibly due to variation in time and amount of feed ingested prior to the measurement. However, while repeated measurements add value; it is preferable the measures be separated by at least 3 to 14 days. This temporal separation of measurements needs to be investigated further. Given the above issue can be resolved, short term (over minutes to hours) measurements of CH4 emissions show promise, especially on systems where animals are fed ad libitum and frequency of meals is high. However, we believe that for short-term measurements to be useful for genetic evaluation, a number (between 3 and 20) of measurements will be required over an extended period of time (weeks to months). There are opportunities for using short-term measurements in standardised feeding situations such as breath 'sniffers' attached to milking parlours or total mixed ration feeding bins, to measure CH4. Genomic selection has the potential to reduce both CH4 emissions and MY, but measurements on thousands of individuals will be required. This includes the need for combined resources across countries in an international effort, emphasising the need to acknowledge the impact of animal and production systems on measurement of the CH4 trait during design of experiments.

Effects of diets supplemented with sunflower or flax seeds on quality and fatty acid profile of hamburgers made with perirenal or subcutaneous fat.

Steers were fed grass hay or red clover silage based diets containing flaxseed or sunflower seed as sources of 18:3n-3 and 18:2n-6 respectively. Hamburgers were made from triceps brachii and perirenal or subcutaneous fat. Perirenal-hamburgers contained more polyunsaturated fatty acids (PUFA), several PUFA biohydrogenation intermediates (BHI), and 18:0 (P<0.05). Oxidative stability was similar across hamburgers (P>0.05). Sensory differences were found due to hamburger fat source, but were < one panel unit. Within perirenal-hamburgers, feeding flaxseed increased 18:3n-3 and its BHI (P<0.05), and feeding sunflower seed increased 18:2n-6 and its BHI (P<0.05). Feeding flaxseed increased off-flavour intensity and oxidation in perirenal-hamburgers (P<0.05). Feeding oilseeds in forage based diets while using perirenal fat to make hamburgers provides opportunities to increase PUFA and BHI with potential to impact human health, but control measures need to be explored to limit oxidation and off-flavours when feeding flaxseed.

Reliability of molecular breeding values for Warner-Bratzler shear force and carcass traits of beef cattle - an independent validation study.

Interest in genetic improvement of carcass and tenderness traits of beef cattle using genome-based selection (GS) and marker-assisted management programs is increasing. The success of such a program depends on the presence of linkage disequilibrium between the observed markers and the underlying QTL as well as on the relationship between the discovery, validation, and target populations. For molecular breeding values (MBV) predicted for a target population using SNP markers, reliabilities of these MBV can be obtained from validation analyses conducted in an independent population distinct from the discovery set. The objective of this study was to test MBV predicted for carcass and tenderness traits of beef cattle in a Canadian-based validation population that is largely independent of a United States-based discovery set. The discovery data set comprised of genotypes and phenotypes from >2,900 multibreed beef cattle while the validation population consisted of 802 crossbred feeder heifers and steers. A bivariate animal model that fitted actual phenotype and MBV was used for validation analyses. The reliability of MBV was defined as square of the genetic correlation (R(2) g) that represents the proportion of the additive genetic variance explained by the SNP markers. Several scenarios involving different starting marker panels (384, 3K, 7K, and 50K) and different sets of SNP selected to compute MBV (50, 100, 200, 375, 400, 600, and 800) were investigated. Validation results showed that the most reliable MBV (R(2) g) were 0.34 for HCW, 0.36 for back fat thickness, 0.28 for rib eye area, 0.30 for marbling score, 0.25 for yield grade, and 0.38 for Warner-Bratzler shear force across the different scenarios explored. The results indicate that smaller SNP panels can be developed for use in genetic improvement of beef carcass and tenderness traits to exploit GS benefits.

Types of oilseed and adipose tissue influence the composition and relationships of polyunsaturated fatty acid biohydrogenation products in steers fed a grass hay diet.

The current study evaluated the composition and relationships of polyunsaturated fatty acid biohydrogenation products (PUFA-BHP) from the perirenal (PRF) and subcutaneous fat (SCF) of yearling steers fed a 70 % grass hay diet with concentrates containing either sunflower-seed (SS) or flaxseed (FS). Analysis of variance indicated several groups or families of structurally related FA, and individual FA within these were affected by a number of novel oilseed by fat depot interactions (P < 0.05). Feeding diets containing SS increased the proportions of non-conjugated 18:2 BHP (i.e., atypical dienes, AD) and conjugated linoleic acids (CLA) with the first double bond from carbon 7 to 9, trans-18:1 isomers with double bonds from carbon 6 to 12, and these PUFA-BHP had greater proportions in SCF compared to PRF (P < 0.05). Enrichment of conjugated linolenic acids, AD and CLA isomers with the first double bond in position 11 or 12, and t-18:1 isomers with double bonds from carbon 13 to 16 were achieved by feeding diets containing FS, with PRF having greater proportions than SCF (P < 0.05). Principal component analysis visually confirmed interaction effects on these groups/families of FA, and further confirmed or suggested a number of relationships between PUFA-BHP. Feeding SS or FS in a grass hay diet and exploiting adipose tissue differences, therefore, present unique opportunities to differentially enrich a number of PUFA-BHP which seem to have positive health potential in humans (i.e., t11-18:1, c9,t11-18:2 and c9,t11,c15-18:3).

Prediction of residual feed intake for first-lactation dairy cows using orthogonal polynomial random regression.

Residual Feed Intake (RFI) is a measure of energy efficiency. Developing an appropriate model to predict expected energy intake while accounting for multifunctional energy requirements of metabolic body weight (MBW), empty body weight (EBW), milk production energy requirements (MPER), and their nonlinear lactation profiles, is the key to successful prediction of RFI in dairy cattle. Individual daily actual energy intake and monthly body weight of 281 first-lactation dairy cows from 1 to 305 d in milk were recorded at the Dairy Research and Technology Centre of the University of Alberta (Edmonton, AB, Canada); individual monthly milk yield and compositions were obtained from the Dairy Herd Improvement Program. Combinations of different orders (1-5) of fixed (F) and random (R) factors were fitted using Legendre polynomial regression to model the nonlinear lactation profiles of MBW, EBW, and MPER over 301 d. The F5R3, F5R3, and F5R2 (subscripts indicate the order fitted) models were selected, based on the combination of the log-likelihood ratio test and the Bayesian information criterion, as the best prediction equations for MBW, EBW, and MPER, respectively. The selected models were used to predict daily individual values for these traits. To consider the body reserve changes, the differences of predicted EBW between 2 consecutive days were considered as the EBW change between these days. The smoothed total 301-d actual energy intake was then linearly regressed on the total 301-d predicted traits of MBW, EBW change, and MPER to obtain the first-lactation RFI (coefficient of determination=0.68). The mean of predicted daily average lactation RFI was 0 and ranged from -6.58 to 8.64 Mcal of NE(L)/d. Fifty-one percent of the animals had an RFI value below the mean (efficient) and 49% of them had an RFI value above the mean (inefficient). These results indicate that the first-lactation RFI can be predicted from its component traits with a reasonable coefficient of determination. The predicted RFI could be used in the dairy breeding program to increase profitability by selecting animals that are genetically superior in energy efficiency based on RFI, or through routinely measured traits, which are genetically correlated with RFI.

Reducing GHG emissions through genetic improvement for feed efficiency: effects on economically important traits and enteric methane production.

Genetic selection for residual feed intake (RFI) is an indirect approach for reducing enteric methane (CH4) emissions in beef and dairy cattle. RFI is moderately heritable (0.26 to 0.43), moderately repeatable across diets (0.33 to 0.67) and independent of body size and production, and when adjusted for off-test ultrasound backfat thickness (RFI fat) is also independent of body fatness in growing animals. It is highly dependent on accurate measurement of individual animal feed intake. Within-animal repeatability of feed intake is moderate (0.29 to 0.49) with distinctive diurnal patterns associated with cattle type, diet and genotype, necessitating the recording of feed intake for at least 35 days. In addition, direct measurement of enteric CH4 production will likely be more variable and expensive than measuring feed intake and if conducted should be expressed as CH4 production (g/animal per day) adjusted for body size, growth, body composition and dry matter intake (DMI) or as residual CH4 production. A further disadvantage of a direct CH4 phenotype is that the relationships of enteric CH4 production on other economically important traits are largely unknown. Selection for low RFI fat (efficient, -RFI fat) will result in cattle that consume less dry matter (DMI) and have an improved feed conversion ratio (FCR) compared with high RFI fat cattle (inefficient; +RFI fat). Few antagonistic effects have been reported for the relationships of RFI fat on carcass and meat quality, fertility, cow lifetime productivity and adaptability to stress or extensive grazing conditions. Low RFI fat cattle also produce 15% to 25% less enteric CH4 than +RFI fat cattle, since DMI is positively related to enteric methane (CH4) production. In addition, lower DMI and feeding duration and frequency, and a different rumen bacterial profile that improves rumen fermentation in -RFI fat cattle may favor a 1% to 2% improvement in dry matter and CP digestibility compared with +RFI fat cattle. Rate of genetic change using this approach is expected to improve feed efficiency and reduce enteric CH4 emissions from cattle by 0.75% to 1.0% per year at equal levels of body size, growth and body fatness compared with cattle not selected for RFI fat.

Effects of feeding flaxseed or sunflower-seed in high-forage diets on beef production, quality and fatty acid composition.

Yearling steers were fed 70:30 forage:concentrate diets for 205 d, with either grass hay (GH) or red clover silage (RC) as the forage source, and concentrates containing either sunflower-seed (SS) or flaxseed (FS), each providing 5.4% oil to diets. Feeding diets containing SS versus FS significantly improved growth and carcass attributes (P<0.05), significantly reduced meat off-flavor intensity (P<0.05), and significantly increased intramuscular proportions of vaccenic (t11-18:1), rumenic (c9,t11-CLA) and n-6 fatty acids (FA, P<0.05). Feeding diets containing FS versus SS produced significantly darker and redder meat with greater proportions of atypical dienes (P<0.05). A significant forage × oilseed type interaction (P<0.05) was found for n-3 FA, α-linolenic acid, and conjugated linolenic acid, with their greatest intramuscular proportions found when feeding the RC-FS diet. Feeding GH versus RC also significantly improved growth and carcass attributes, sensory tenderness (P<0.05) and significantly influenced intramuscular FA composition (P<0.05), but overall, forage effects on FA profiles were limited compared to effects of oilseed.