PSI-20 Effects of management system on heifer growth performance and fescue toxicity

Abstract

Abstract The objective was to determine the effects of beef heifer management system on growth performance and fescue toxicity. Fall-born Angus × Simmental heifers (n = 199; BW = 229 ± 24 kg] were stratified by BW into 12 groups and groups were randomly assigned to 1 of 4 treatments: dry-lot developed (DL); grazing endophyte-infected fescue supplemented with 2.3 kg dried distiller’s grains with solubles (DDGS) and soybean hulls per heifer daily (GF); grazing endophyte-infected fescue supplemented with 4.5 kg DDGS and soybean hulls per heifer daily from the midpoint of experimental period until breeding (GFLate); and grazing novel endophyte-infected fescue (GNF). The DL heifers were ad-lib fed a diet consisting of 70% hay and 30% DDGS. Experiment began in May and ended at time of AI. There was a treatment × time interaction (P < 0.01) for BW, BCS, HCS, and RR. There were no BW differences (P = 0.99) at trial initiation; however, on d 28, 56, 84, 112, and 148, DL heifers had greatest (P < 0.01) BW, with GF intermediate, and GFLate and GNF having the lightest BW. There were no BCS differences (P = 0.42) at trial initiation; however, on d 56 and 84, DL heifers had greatest (P < 0.01) BCS, with GF intermediate, and GFLate and GNF the lowest. On d 148, DL heifers had greater (P < 0.01) BCS than GF, GFLate, and GNF which were not different from each other. There were no HCS differences (P = 0.51) at trial initiation; however, on d 28, 84,112, and 148, GFLate had the greatest (P ≤ 0.03) HCS. For RR, DL had the greatest (P < 0.01) RR on d 28; on d 56, GNF had greatest (P < 0.01) RR; and at d 112, GFLate had greatest (P < 0.01) and DL least (P < 0.01) RR. Heifer management system impacted symptoms of fescue toxicity and heifers developed in a dry lot had the greatest BW and BCS.