Genetic potential for residual feed intake and diet fed during early- to mid-gestation influences post-natal DNA methylation of imprinted genes in muscle and liver tissues in beef cattle.

Discovery of epigenetic modifications associated with feed efficiency or other economically important traits would increase our understanding of the molecular mechanisms underlying these traits. In combination with known genetic markers, this would provide opportunity to improve genomic selection accuracy in cattle breeding programs. It would also allow cattle to be managed to improve favorable gene expression. The objective of this study was to identify variation in DNA methylation between beef cattle of differential pre-natal nutrition and divergent genetic potential for residual feed intake (RFI). Purebred Angus offspring with the genetic potential for either high (HRFI) or low (LRFI) RFI were prenatally exposed to either a restricted maternal diet of 0.5 kg/d average daily gain (ADG) or a moderate maternal diet of 0.7 kg/d ADG from 30 to 150 d of gestation. We performed DNA methylation analysis of differentially methylated regions (DMR) of imprinted genes (Insulin-like growth factor 2 (IGF2) DMR2, IGF2/H19 imprinting control region (ICR) and IGF2 receptor (IGF2R) DMR2) using post-natal samples of longissimus dorsi (LD) muscle taken from male and female calves at birth and weaning, and of LD muscle, semimembranosus (SM) muscle, and liver samples collected from steers at slaughter (17 months of age). Interestingly, for all three DMR investigated in liver, LRFI steers had higher levels of methylation than HRFI steers. In LD muscle, IGF2/H19 ICR methylation differences for heifers at birth were due to pre-natal diet, while for steers at birth they were mostly the result of genetic potential for RFI with LRFI steers again having higher levels of methylation than HRFI steers. While results from repeated measures analysis of DNA methylation in steers grouped by RFI revealed few differences, in steers grouped by diet, we found higher methylation levels of IGF2 DMR2 and IGF2R DMR2 in LD muscle of restricted diet steers at weaning and slaughter than at birth, as well as increased methylation in LD muscle of restricted diet steers compared with moderate diet steers at weaning and/or slaughter. Our results suggest that differential pre-natal nutrition, and divergent genetic potential for RFI, induces tissue- and sex-specific alterations in post-natal IGF2 and IGF2R methylation patterns and that these patterns can vary with age in Angus beef cattle.

Phenotypic and genetic correlations of beef replacement heifer feeding behaviour, feed intake and feed efficiency with cow performance and lifetime productivity.

Objectives were to quantify the phenotypic (rp ) and genetic (rg ) correlations between early-life feeding behaviours, dry matter intake, and feed efficiency and measures of cow performance and lifetime productivity traits. Traits were measured on 1,145 crossbred replacement beef heifers and then on cows over parities one to four. Feeding event duration (FD) was phenotypically correlated with cow prebreeding body weight (PBWT; rp 0.29-0.45), cow prebreeding back fat thickness (PBBF; rp 0.35-0.49), progeny weaning weight (WW; rp 0.09-0.31) and progeny birthweight (BW; rp -0.06 to 0.17). Feeding event frequency (FF) was phenotypically correlated with PBBF (rp 0.16-0.30). Dry matter intake (DMI) was phenotypically correlated with PBWT (rp 0.16-0.20) and PBBF (rp -0.22 to -0.05). Feeding event duration was genetically correlated with PBWT (rg 0.38-0.41). Feeding event frequency was genetically correlated with PBWT (rg -0.43 to -0.39). Dry matter intake was genetically correlated with PBWT (rg -0.27 to 0.14). Days in herd (DIH) was phenotypically correlated with FD and DMI (rp  = 0.12, 0.20, respectively). Lifetime productivity was phenotypically correlated with FD and FF (rg  = 0.25, 0.22, respectively). Calving interval was phenotypically correlated with FD and FF (rp  = -0.12, -0.14, respectively) and genetically correlated with FF (rg  = -0.41). Due to moderate positive correlations with cow weight, caution would be required in selection to prevent an increase in mature cow size. Use of FF, FD, DMI and a measure of feed efficiency such as residual feed intake adjusted for back fat (RFIFAT ) in a balanced selection index is recommended.

Improving beef hamburger quality and fatty acid profiles through dietary manipulation and exploitation of fat depot heterogeneity.

BACKGROUND: Hamburger is the most consumed beef product in North America, but lacks in nutritional appeal due to its high fat content and high proportion of saturated fatty acids (SFA). Objectives of the present study were to improve the FA profiles of hamburgers made with perirenal fat (PRF) and subcutaneous fat (SCF) when feeding steers different diets along with examining differences in sensory attributes and oxidative stability. Diets included a control diet containing 70:30 red clover silage: barley based concentrate, a diet containing sunflower-seed (SS) substituted for barley, and diets containing SS with 15% wheat dried distillers' grain with solubles (DDGS-15) or 30% DDGS (DDGS-30). Hamburgers were made from triceps brachii and either PRF or SCF (80:20 w/w). RESULTS: Perirenal fat versus SCF hamburgers FA had 14.3% more (P <0.05) 18:0, 11.8% less cis (c)9-18:1 (P <0.05), and 1.82% more total trans (t)-18:1 mainly in the form of t11-18:1. During sensory evaluation, PRF versus SCF hamburgers had greater (P <0.05) mouth coating, but the difference was less than one panel unit. Examining effects of steer diet within PRF hamburgers, feeding the SS compared to the control diet increased (P <0.05) t-18:1 by 2.89% mainly in the form of t11-18:1, feeding DGGS-15 diet led to no further changes (P >0.05), but feeding DDGS-30 diet reduced the proportions of (P <0.05) of t-18:1 chiefly t11-18:1. Feeding SS and DDGS diets had small but significant (P <0.05) effects on hamburger sensory attributes and oxidative stability. CONCLUSIONS: Feeding high-forage diets including SS and 15% DDGS, and taking advantage of the FA heterogeneity between fat depots offers an opportunity to differentially enhance beef hamburgers with 18:2n-6 biohydrogenation products (i.e., t11-18:1) with potential human health benefits without compromising their sensory attributes and oxidative stability during retail display.

Effect of soil composition, temperature, indigenous microflora, and environmental conditions on the survival of Escherichia coli O157:H7.

The survival of Escherichia coli O157:H7 in replicate soil microcosms was quantified in 2 types of silty clay loam soil (high carbon and low carbon) under either sterile or nonsterile conditions. Microcosms were held at -21, 4, and 22 degrees C under constant soil moisture content. Differences existed (P < 0.05) in survival of E. coli O157:H7 in low- and high-carbon soil at all temperatures, indicating an important role of soil composition on the survival of this pathogen. The highest death rate of E. coli O157:H7 in sterile soil occurred in the low-carbon soil at 4 degrees C, whereas in nonsterile soil the highest death rate was observed in the low-carbon soil at 22 degrees C. These results suggest that the most lethal effects on E. coli O157:H7 in the sterile system occurred via the synergy of nutrient limitation and cold stress, whereas in the nonsterile system lethality was owing to inhibition by indigenous soil microorganisms and starvation. Results obtained from an in situ field survival experiment demonstrated the apparent sensitivity of E. coli O157:H7 cells to dehydration, information that may be used to reduce environmental spread of this pathogen as well as formulate appropriate waste management strategies.