Concentrate Supplementation Effects on Forage Characteristics and Performance of Early Weaned Calves Grazing Rye–Ryegrass Pastures

Abstract

Early weaning of calves ( Bos spp.) increases pregnancy rates of beef cows; however, there is little information on nutritional management of the weaned calf on pasture. This research evaluated the effect of concentrate supplementation level on performance of early weaned (90 d of age) beef calves grazing annual ryegrass ( Lolium multiflorum Lam.)–rye ( Secale cereale L.) mixtures on Adamsville (uncoated, hyperthermic, Aquic Quartzipsamment) and Pomona (sandy, siliceous, hyperthermic Ultic Alaquod) sands. Three levels of supplement (10, 15, and 20 g kg −1 of calf body weight [BW]) were evaluated in a completely randomized design with three replicates. The concentrate contained 146 and 700 g kg −1 of crude protein (CP) and total digestible nutrients (TDN). Pastures were rotationally stocked with a 7‐d grazing and 21‐d rest period. Two calves were assigned as testers to each pasture, and additional animals were used to maintain a similar herbage allowance across treatments. There was no effect of concentrate supplementation level on herbage mass, accumulation, allowance, or nutritive value. Calf average daily gain (ADG; 0.74–0.89 kg), liveweight gain (LWG) per hectare (950–1320 kg), and stocking rate (SR; 5.5–6.5 animal units [AU] ha −1 ) increased linearly, and forage intake decreased linearly (18–11 g kg −1 BW) as concentrate rate increased. Grazing time was 284, 230, and 234 min d −1 (linear and quadratic effects) for the 10, 15, and 20 g kg −1 BW supplement treatments, respectively. Feeding systems with modest levels of supplementation (10 g kg −1 BW) of calves grazing cool‐season grasses are practical options for early weaned calves during winter in the southeastern USA.