Effects of Diet on Intake and Methane Emissions of Beef Steers

Abstract Text:  Objectives of this study were to determine the effects of diet type on feed intake and methane emissions of beef steers. Fistulated steers (n = 12; BW = 725 ± 120 kg) were used in a crossover design with 2 dietary treatments: high forage (HF; 85% chopped grass hay, 10% alfalfa haylage, 5% supplement), or high grain (HG; 60% dry cracked corn, 20% corn silage, 10% dry distillers grains with solubles, and 10% supplement). Intake was evaluated for 18d via GrowSafe. Steers were then fed for 24hr in environmentally controlled, hood-type chambers during which CH₄ concentrations were measured. While steers were in CH₄ collection chambers, rumen gas was also collected via cannula puncture at 0, 3, and 9hr post-feeding and analyzed for CH₄ concentration. Steers fed HG had greater (P ˂ 0.01) DMI than steers fed HF. When steers were fed in gas collection chambers, DMI decreased (P ˂ 0.01) compared to when fed in GrowSafe, regardless of diet; however, DMI during CH₄ collection was correlated to DMI during the GrowSafe period (r = 0.73; P ˂ 0.01). Daily CH₄ production and g CH₄ per kg BW did not differ (P ≥ 0.11). However, g CH₄ per kg DMI was greater (trend; P = 0.09) for steers fed HF than steers fed HG. Furthermore, diet did not impact ruminal CH₄ concentrations (P = 0.81). Daily CH₄ production was correlated to ruminal CH₄ concentration at 0hr (r = 0.54; P ˂ 0.01), tended to be correlated at 3hr (r = 0.38; P = 0.07), but was not correlated at 9hr (r = 0.33; P = 0.12). Methane production per kg BW was correlated to rumen CH₄ concentration at 0hr (r = 0.52; P = 0.01), tended to be correlated at 3hr (r = 0.41; P = 0.06), but, again, was not correlated at 9hr (r = 0.33; P = 0.12). Steers fed HG diets had greater DMI compared to those fed HF, supporting previous research. Although diet did not impact daily CH₄ production, g CH₄ per kg steer BW, or ruminal CH₄ concentrations, g CH₄ per kg DMI was greater for steers fed forage-based diets than for steers fed grain-based diets.  

Keywords:  beef cattle, intake, methane