99 Dietary Inclusion of a High-Anthocyanin Corn Cob Meal into Feedlot Rations Reducesin Vitro Methane Emissions

Abstract

Abstract Methane (CH4) is a greenhouse gas associated with global warming that is released as a byproduct of rumen fermentation. Two experiments were conducted to determine if dietary inclusion of a novel high anthocyanin (Hi-A) containing corn cob meal [CCM; 4.99 mg anthocyanin×g-1 of dry matter (DM)] influences in vitro CH4 emissions relative to a conventional CCM (CNV; 0.04 mg anthocyanin×g-1 of DM). High-roughage starter (experiment 1) and low-roughage finisher (experiment 2) diets were formulated to contain 20% and0% total CCM (DM-basis), respectively. Treatments were based on the proportion of Hi-A to CNV CCM within each diet and consisted of 0% (0A), 25% (25A), 50% (50A), 75% (75A), and 100% Hi-A (100A) CCM. In experiments 1 and 2, ruminal fluid was collected from 4 cannulated steers offered traditional feedlot starter or finisher diets, respectively. Filter bags (F57; ANKOM; Macedon, NY) were loaded with 0.5 g of substrate and 2 bags per ANKOM RF system were incubated in buffer and rumen fluid for 48 h at 39°C. Cumulative gas production was recorded at 10-min intervals. The concentration of CH4 as a proportion of total gas production (%CH4) was measured using gas chromatography after 48 h. Total gas production was fit to the Ørskov model to determine asymptotic and fractional rates of gas production. In experiment 1, there was a cubic relationship between total gas production and Hi-A CCM inclusion for the intercept, asymptote, and fractional gas production rate (P ≤ 0.04). There was also a cubic relationship between %CH4 and Hi-A CCM inclusion (P = 0.04), where 50A had the largest reduction relative to 0A at -19.6% (P = 0.05). Total CH4 production (mL CH4×g DM-1) also exhibited a cubic relationship with Hi-A-CCM inclusion (P = 0.03), where 100A produced 20% less CH4 than 0A. In experiment 2, there was a cubic relationship between total gas production and Hi-A CCM inclusion for the intercept and asymptote (P ≤ 0.02) of the Ørskov model; however, fractional gas production rate expressed a quadratic relationship (P < 0.01). Furthermore, a cubic relationship existed between %CH4 and Hi-A CCM inclusion, where 100A had the largest reduction relative to 0A (17.4%; P = 0.03). Lastly, there was a tendency for a cubic relationship between Hi-A CCM inclusion and total CH4 production (P = 0.06); however, 100A reduced total CH4 production by 22% relative to 0A (P = 0.01). Collectively, the greatest level of Hi-A CCM inclusion reduced total CH4 production relative to 0A in both starter and finisher diets. These results indicate that dietary inclusion of anthocyanins through CCM decreased CH4 emissions in vitro. Further research is needed to determine if anthocyanins from Hi-A CCM are effective at mitigating CH4 emissions in vivo.