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Effect of Supplemenation Method on Supplement Intake and Performance of Steers Grazing Dormant Tallgrass Prairie.

Williams, Garret Don
The objective of this experiment was to determine the effect of supplementation method (hand-fed vs. ad-libitum access) on supplement intake and performance of beef steers grazing dormant native tallgrass prairie. The experiment was conducted for 56 d in late winter in central Oklahoma. Angus x Hereford steers (n = 40; BW = 242.6 ± 3.6 kg) were randomly assigned to one of three supplementation methods; either control (CON; no supplement; n = 8), hand-fed (HF; n = 16), or self-fed (SF; n = 16). Both the HF and SF treatments received a supplement consisting of 80% soybean meal and 20% soybean hulls (TDN = 76.6 %, CP = 43.9 %; DM basis). Sixteen steers were assigned to the HF, where 4 steers received either 0.39, 0.78, 1.17, or 1.56 kg per day, fed 3 days per week in individual stanchions. Sixteen steers were assigned to the SF group and received supplement via the SmartFeed system (C-Lock Inc., Rapid City, South Dakota). The SmartFeed is a portable, self-contained system designed to measure individual feed intake. The SF group had ad libitum access to supplement, to which NaCl was added to achieve mean intake of approximately 1.0 kg/d. The overall mean intake of supplement in SF ranged from 0 to 1.21 kg per steer per day. The CV for the SF animal on mean intake was 50.8% and animal on day-to-day intake was 96.7%. The mean NaCl that was present in the SF supplement was 40.5% and NaCl intake averaged 0.39 kg/d. Steers were weighed weekly and ADG and supplement efficiency was regressed on supplement intake, supplementation method, and the interaction. No significant difference between treatment group was detected for ADG (P = 0.24) or supplement efficiency (P = 0.30) regressions. Aggregated CV of weekly intake with animal significantly (P ? 0.01) decreased residual ADG and residual supplement efficiency. Steers grazing dormant tallgrass prairie with minimal change in weekly supplement intakes had a slightly greater ADG and supplement efficiency. Directly managing supplementation may be more efficient than traditional, self-fed approaches that rely on NaCl as a limiter.