Effects of forage allowance and supplementation on performance of steers grazing winter wheat pasture

Abstract

A study was conducted over two fall/winter wheat grazing seasons (2018 - 2020) to estimate the combined effect of forage allowance and a fiber-based energy supplement in stocker cattle grazing wheat. Eight pastures (2.7 to 5.1 ha) were stocked with seven test steers (initial BW = 210 ± 36 kg). Weekly, additional steers were added or removed in each pasture, a put and take method, to achieve forage allowance of either 1.5 or 3.0 kg forage DM / kg steer BW (4 pastures each). Two pastures in each forage allowance were fed daily with a supplement containing 50% wheat middlings and 50% soybean hulls at the rate of 1.5 kg (as fed) per steer. Forage mass was measured twice weekly using a calibrated rising plate meter. Cattle were weighed weekly on calibrated scales. Data were analyzed using linear regression with pasture as the experimental unit. Mean ADG was 1.49 ± 0.36 kg/d. One pasture in the high forage allowance, non-supplemented treatment was removed from analysis in year one because desired forage allowance could not be maintained. There was an interaction of forage allowance and supplementation on ADG (P = 0.053) such that cattle receiving greater forage allowance with supplementation produced greater daily gains. To further investigate forage DMI, a 14-d trial began on day 36 in each year. Three of the seven test steers in each pasture were randomly selected to receive 7 ± 0.1 g of TiO2 daily at 0700 as an external marker to estimate fecal output. Forage DMI averaged 2.03% of midpoint BW, below our expectation. There was no interaction of forage allowance and supplementation (P = 0.14) on forage DMI. Forage allowance affected forage DMI (P = 0.04), but supplementation had no effect (P = 0.37).