Variability in supplement intake affects performance of beef steers grazing dormant tallgrass prairie

The objective of this experiment was to determine the effect of the variability associated with different supplementation methods (hand-fed vs. self-fed) on supplement intake and performance of beef steers grazing dormant tallgrass prairie. Angus × Hereford steers (n = 40; BW = 243 ± 23 kg) were randomly assigned to 1 of 3 supplementation methods: control (no supplement; n = 8), hand-fed (HF; n = 16), or self-fed (SF; n = 16). The supplement was 80% soybean meal and 20% soybean hulls (NEg = 1.18 Mcal/kg, CP = 43.9%; DM basis). In HF, individual steers received 0.39, 0.78, 1.17, or 1.56 kg per day, in 3 feedings per week in stanchions (supplement only; no added NaCl). The SF steers received supplement via an electronic self-feeder that recorded individual intake but with NaCl added to achieve mean intake of approximately 1.0 kg/d of the base supplement. The overall mean intake of base supplement in SF ranged from 0 to 1.21 kg per steer per day. In SF, the CV for 56-d intake across animals was 51%, whereas the CV for intake across day within animal was 72%. Steers were weighed weekly; ADG and supplement efficiency [(ADG − ADG of controls)/supplement intake] were regressed on supplement intake and supplementation method, but no interaction was detected (P > 0.32). To investigate the effect of variability directly, supplement efficiency residual of supplement intake was regressed on CV of weekly supplement intake. This approach indicated that increased variability in supplement intake was detrimental to efficiency (P ≤ 0.02).