Cost of Steer Weight Gain to Rate of Supplementation with Ground Corn on Bermudagrass Pasture

Cattle ( Bos sp.) weight gain on bermudagrass [ Cynodon dactylon (L.) Pers.] pastures declines in the middle to late grazing season regardless of forage supply. Nutrient supplementation with concentrates is an option for boosting average daily gain (ADG), but economic feasibility of this management is not clearly understood. A grazing experiment was conducted in 1998 and 1999 with yearling steers grazing bermudagrass to evaluate ADG and costs as amounts of supplemented ground corn ( Zea mays L.) (0, 0.45, 1.35, and 2.25 kg steer −1 d −1 ) increased and to monitor seasonal changes in bermudagrass in vitro digestible dry matter and crude protein (CP) concentration. There was a curvilinear increase in ADG as supplementation was increased from 0 and 1.35 kg steer −1 d −1 , but ADG stabilized between the 1.35‐ and 2.25‐kg rates. In vitro digestible dry matter and CP concentrations declined over the two grazing seasons, but CP concentration increased following the second application of N fertilizer in 1998 when rainfall was adequate for bermudagrass growth and N uptake. Cost of additional ADG from supplementation tended to be lowest for the 1.35 kg steer −1 d −1 supplementation rate over a range in corn costs from $90 to $250 Mg −1 . The 1.35‐kg supplementation rate provided costs of additional ADG that were lower than break‐even costs for low ($1.32 kg −1 liveweight), intermediate ($1.77 kg −1 liveweight), and high ($2.20 kg −1 liveweight) cattle prices. Costs of additional ADG for the 0.45‐ and 2.25‐kg supplementation rates were lower than the break‐even costs for high cattle prices when corn costs were less than $170 and $190 Mg −1 , respectively. Supplementation with ground corn at rates of 0.45 to 1.35 kg steer −1 d −1 can cost effectively enhance weight gain of yearling steers grazing bermudagrass.