Effects of implant type and protein source on growth of steers grazing summer pasture1

A split-plot design was used to investigate the effects of implant type and protein source on performance of steers grazing summer pasture. Each year, 196 steers were stratified by arrival weight (216 ± 24 kg and 208 ± 23 kg for 2008 and 2009, respectively) and randomly allotted to 1 of 3 implant treatments in early June. Implant treatments were no implant (control), Ralgro (Schering-Plough Animal Health Corp., Union, NJ), and Component TE-G (Ivy Animal Health, Overland Park, KS). Supplement treatments were no supplement (control), cottonseed meal-based supplement (CSM; 33% CP), and dried distillers grains-based supplement (DDGS; 33% CP). Supplementation began in late July, and supplements were group fed, within pasture, 3 times each week at a rate of 0.95 kg/steer (DM basis). Supplementation increased BW and ADG by 12 and 0.16 kg, respectively (P < 0.05). Rate of BW gain was also improved by 0.05 kg (P < 0.05) for DDGS as compared with CSM, resulting in 2.67 versus 3.78 kg of supplement per kilogram of additional ADG for DDGS and CSM, respectively. Implantation increased final BW (P = 0.02) and improved ADG 8.1% (P = 0.01) during the first ~ 95 d, regardless of implant type. However, Component TE-G increased ADG (0.08 kg; P = 0.01) the final ~ 31 d of the grazing season as compared with control and Ralgro-implanted cattle. Responses to supplement and implant programs were additive. Supplementing DDGS and implanting with Component TE-G were the most economical programs during the 126-d grazing season.