159 Evaluation of Supplemental Feeding Behavior and Growth Performance in Katahdin Lambs Divergently Selected for Fecal Egg Count Estimated Breeding Value

Abstract

Abstract Nutritional supplementation and genetic selection are potential methods to mitigate the impact of parasitism in sheep. Understanding feeding behavior of growing lambs divergently selected for parasite resistance using the fecal egg count (FEC) estimated breeding value (EBV) may help quantify the impact of supplementation and genetic selection on parasitism. The C-Lock, Inc Super SmartFeed system (feeder) allows measurement of individual lamb feed intake. The objective of this study was to evaluate the effect of FEC EBV selection on daily supplemental intake, average daily gain (ADG), supplemental feed:gain (S:G), frequency of feeder visits, and FEC. Over two years (Y1, Y2), Katahdin lambs divergently selected for FEC EBV (Y1: LowFEC, n = 27; HighFEC, n = 24. Y2: LowFEC, n = 37; HighFEC, n = 40) were fed for 8 weeks in Y1 and 5 weeks in Y2 at the Southwest Virginia Agricultural Research and Extension Center. Pasture-raised lambs were supplemented with a concentrate pellet (16% CP) ad libitum using the feeder with free choice hay in a dry lot post-weaning. Data analyses were performed by sampling period which was approximately every two weeks. Statistical analyses were performed using PROC Mixed SAS (SAS Institute, Cary, NC). In Y1, LowFEC lambs had less average FEC than HighFEC lambs (405.25 vs. 771.23 epg; P < 0.05). LowFEC lambs in Y2 tended to have less average FEC compared with HighFEC lambs (1,191.75 vs. 2,028.30 epg; P = 0.1). In Y1, LowFEC lambs had greater intake compared with HighFEC lambs (1.45 vs. 1.27 kg; P < 0.05). LowFEC lambs tended to have greater intake in Y2 (1.64 vs. 1.16 kg; P = 0.1). While ADG was not affected by FEC EBV type in Y1 (P > 0.70), LowFEC lambs in Y2 had increased ADG compared with HighFEC lambs (0.27 kg vs. 0.21 kg; P = 0.05). In both years, LowFEC lambs had numerically greater S:G compared with HighFEC lambs, but these differences were not significant (P > 0.1) due to greater variation around these means. Over both years, the number of feeder visits did not differ between LowFEC and HighFEC lambs (P > 0.1). Selection of sires for LowFEC EBV resulted in progeny with less FEC that had increased supplemental intake, but no difference in S:G compared with HighFEC progeny. In addition to improvements in parasite resistance, selection for FEC EBV may impact lamb feeding behavior in the post-weaning period.