PSVII-30 - Winter-feeding high concentrate diets reduces enteric methane emissions pre-calving in beef cows

Abstract: Objectives were to evaluate the effects of winter-feeding forage (2.02 Mcal/kg dietary ME) vs. concentrate (2.84 Mcal/kg of dietary ME) diets pre- and post- calving on enteric methane emissions, dry matter intake (DMI), and performance of beef cows. Forty-six pregnant (210 ± 10 d of gestation) Angus and Simmental-Angus cows (BW = 630 ± 12.0 kg) were blocked by breed, age, and body weight and assigned to one of two treatments: 1) Ad-libitum feeding of forage-based diet (HFOR; n = 23); or 2) a concentrate corn-based diet with a restricted intake of 1.2% BW (HCON; n = 23). Cows were housed in a group-pen at the South Dakota State University Cow-Calf Education and Research Facility (Brookings, SD). Feed consumption was tracked using an electronic feeder (Insentec, The Hague, Netherlands) and enteric methane emissions were monitored using the GreenFeed trailer system (C-Lock Inc., Rapid City, SD). Body weight measurements were taken bi-weekly. Treatments started being applied on d 50 (± 10) pre-calving and will continue to be applied up to d 84 post-calving. Preliminary data reported herein was collected from d 42 pre-calving up to d 42 post-calving. Performance and dry matter intake data were analyzed as repeated measures using the MIXED procedure of SAS with treatment, period, and their interaction as fixed effects and animal as a random effect. Enteric emissions were analyzed using a linear mixed effects model with animal as a random effect in R, with a post-hoc contrast among treatments. Pre-calving, HFOR had greater (P < 0.01) CH₄ emissions than HCON (264 ± 9.19 g/d and 246 ± 9 g/d for HFOR and HCON, respectively). Both groups presented dynamic changes in CH₄ emissions over time (P < 0.01). Post-calving, no differences were observed between treatments (P = 0.55); however, temporal changes (p < 0.01) and treatment × day interaction (P < 0.01) persisted, indicating ongoing diet-temporal interplay. No treatment × period interactions (P ≥ 0.16) were observed for DMI and performance. As designed, dry matter intake was lower (P < 0.01) for HCON (8.66 ± 0.45 kg) than HFOR (17.3 ± 0.45 kg) cows. Further, dry matter intake was lower (P < 0.01) pre-calving (11.11 ± 0.28 kg) than post-calving (14.85 ± 0.48 kg). Cows in the HFOR group were heavier (P = 0.01) than HCON (646.22 ± 14 kg vs. 593.43 ± 14 kg, respectively) likely due to ruminal fill; and as expected cows were heavier (P < 0.01) pre- than post-calving, with the greatest BW observed on d 14 pre-calving (639.52 ± 9.92 kg). These data indicate that high concentrate corn-based diets may be used in dry-lot settings to optimize nutritional management and reduce methane emissions when compared to conventional high forage winter-feeding strategies.