Evaluation of methane production manipulated by level of intake in growing cattle and corn oil in finishing cattle.

Growing crossbred steers [n = 80, initial body weight (BW) = 274 kg, SD = 21] were used to evaluate the effect of ad libitum and limit-fed intakes on methane (CH4) production. Two treatments with four pens per treatment (10 steers per pen) were evaluated in a randomized block designed experiment, with BW as a blocking factor. Treatments included feeding the same diet at ad libitum intake or limit fed at 75% of ad libitum intakes. Diet consisted of 45% alfalfa, 30% sorghum silage, 22% modified distillers grains plus solubles, and supplement at 3% on a dry matter (DM) basis. This trial was followed by a finishing trial (n = 80; initial BW = 369 kg; SD = 25) to evaluate the effects of dietary corn oil on CH4 production. Two treatments with four pens per treatment (10 steers per pen) were used in a randomized complete block designed experiment. Cattle were rerandomized and blocked by BW within the previous treatment. Treatments consisted of a control diet (CON) containing 66% corn, 15% wet distillers grains plus solubles, 15% corn silage, and 4% supplement (DM basis). Corn oil treatment (OIL) displaced 3% corn by adding corn oil. Methane was collected in two pen-scale chambers by collecting air samples continuously from pens by rotating every 6 min with an ambient sample taken between pen measurements. Steers fed ad libitum had greater DM intake (DMI) by design and greater average daily gain (ADG; P < 0.01) compared to limit-fed cattle; however, feed efficiency was not different between treatments (P = 0.40). Cattle fed ad libitum produced 156 g/d of CH4, which was greater (P < 0.01) than limit-fed cattle (126 g per steer daily). In the finishing trial, BW, gains, and carcass traits were not impacted by treatment (P ≥ 0.14). Feed efficiency (P = 0.02) improved because intakes decreased (P = 0.02) by feeding OIL compared to CON. Daily CH4 production was less (P = 0.03) for OIL-fed cattle (115 g per steer daily) compared to CON-fed cattle (132 g per steer daily). Methane was reduced (P < 0.01) by 17% for OIL-fed cattle compared to CON-fed cattle when expressed as grams of CH4 per kilogram of ADG. Feeding corn oil at 3% of diet DM reduced enteric CH4 production (grams per day) by 15%, which was only partially explained by a 3% decrease in DMI. Overall, a decrease in CH4 was observed when intake is limited in growing cattle and when corn oil is added in finishing diets.