172 Enteric methane emissions from pregnant beef heifers as affected by multiple mitigation strategies

Abstract

Abstract This study was conducted to determine if enteric methane (CH4) emissions from pregnant beef heifers could be reduced by using multiple dietary mitigation strategies. The trial was designed as a 4 x 4 Latin square consisting of a 21-d adaptation phase followed by a 21-d data collection phase. Forty Aberdeen Angus cross pregnant beef heifers were randomly assigned to one of the four dietary treatments (n = 10): i) low protein grass hay (L; 6.1% CP; 1.9% fat); ii) adequate protein grass hay (AD; 10.8% CP; 1.9% fat); iii) AD supplemented with sunflower screenings (ADSS; 9.8% CP; 5.6% fat); and iv) above adequate protein legume grass mix hay (AAD; 12.8% CP; 1.7% fat). Total dry matter intake (DMI) was 32%, 27% and 39% greater (P < 0.0001) for AD, ADSS and AAD respectively, relative to the L diet (6.5 kg d-1). Average daily gain (ADG; kg d-1) was influenced by dietary treatment (P < 0.0001), as heifers offered L, AD, ADSS and AAD diets gained 0 ± 0.2, 0.6 ± 0.2, 0.5 ± 0.2 and 0.7 ± 0.2 kg d-1, respectively. Enteric CH4 emissions (L d-1), were influenced by dietary treatment (P < 0.0001) with 184 ± 18.9, 214 ± 19.0, 204 ± 19.1 and 232 ± 19.1 L d-1 for heifers offered L, AD, ADSS and AAD diets, respectively. Further, heifers offered AD, ADSS and AAD diets emitted 19%, 22% and 14% less (P=0.03) enteric CH4 (% GEI) relative to diet L, respectively. This study demonstrates that supplementation to meet nutrient requirements for protein or increasing the fat content of forage-based diets using low-cost by-products such as sunflower screenings can decrease enteric CH4 emissions without adversely impacting total DMI and ADG.