Effect of daily or alternate-day distillers grains supplementation with or without monensin on performance of grazing calves1

The objective of these experiments was to determine the effect of daily or alternate day supplementation of dried distillers grains with solubles (DDGS) with or without monensin on performance of grazing calves. Treatments included (1) a negative control with no supplemental feed except free-choice mineral; (2) DDGS offered daily at 1.02 kg as-fed per calf, including a mineral premix; (3) daily DDGS and monensin (Rumensin, Elanco, Greenfield, IN) at 1.02 kg as-fed per calf, including a mineral premix supplying 160 mg of monensin/calf daily; (4) alternate day DDGS to supply 2.04 kg as-fed per calf, including the mineral premix offered on alternate days; and (5) alternate day DDGS and monensin to supply 2.04 kg as-fed per calf, including a mineral premix and 320 mg of monensin/calf on alternate days. Four experiments were conducted which included both steers (n = 70) and heifers (n = 230) grazing warm season grass based pastures (Exp. 1, 2, and 3) or nontoxic endophyte-infected tall fescue (Exp. 4). Supplementation increased ADG (P ≤ 0.04) by 0.16 to 0.26 kg/d in the 4 studies, with an average improvement (P < 0.01) of 0.21 kg/d. Monensin addition and supplement timing had no effect (P ≥ 0.16) on BW, ADG, or supplemental efficiency in any of the 4 experiments. Supplementation increased ADG of growing beef calves regardless of pasture quality or basal cattle performance. The performance improvement was similar whether supplements were fed daily or on alternate days. Contrary to expected results, monensin inclusion in the supplement had no effect on animal performance or supplemental efficiency.