283 - Precision versus Group Supplementation at Two Levels on Growth and Development of Replacement Heifers

Two experiments were conducted to evaluate use of the Super SmartFeeder (SSF; C-Lock, Inc.) for individual versus group supplementation of heifers grazing stockpiled, novel tall fescue. In experiment 1, Angus heifers (n = 64; 267 + 31.7 kg) had access to the SSF and were allowed 3.6 kg/d of grower supplement. Individual intake was recorded daily and analyzed to determine adoption. Twenty-four percent of the heifers did not adopt to individual SSF supplementation (P < 0.05). In experiment 2, heifers (n = 64; BW= 275 + 31.3 kg) were allotted, based on adoption to SSF, to supplementation system of group feeding (n = 2 reps/level; GRP) or SSF precision feeding (n =16/level; PRE) at two levels (0.5% or 1% of BW) for 127-d in a 2 x 2 factorial. Data were analyzed using Mixed procedure. The interaction between supplementation level and feeding system tended to be significant (P = 0.10) for overall ADG. Average daily gain was greater for 1% BW than 0.5% BW (0.81 vs. 0.47 kg/d) for PRE but did not differ for GRP (0.69 kg/d). Daily supplement dry matter intake differed (P < 0.05) by supplementation level and total BW gain was greater (P < 0.05) by 24.3 kg for 1% versus 0.5% supplementation level. Ultrasound ribeye area and fat thickness measures were greater (P < 0.05) for 1% BW supplement compared to 0.5% BW at the end of the 127d study. When PRE was analyzed independently, heifer BW differed (P < 0.05) on d 91, 117 and 127 between supplement levels. The correlation between individual heifer daily supplement intake and overall ADG for PRE was 0.68 (P < 0.0001). The use of technology to precisely control intake in a grazing system created greater divergence in growth by supplementation level compared to group feeding systems.