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Understanding the impact of genetic resistance to internal parasitism and infection status on feed efficiency could be valuable to selection and management programs. The aim of this study was to evaluate the effect of fecal egg count (FEC) estimated breeding value (EBV) and Haemonchus contortous (H.C.) infection on intake, feed:gain (F:G), and residual feed intake (RFI). Over two years, Katahdin lambs divergently selected for FEC EBV (LowFEC, n = 86; HighFEC, n = 87) were born mid-March at the Southwest Virginia Agricultural Research and Extension Center. Mid-July, lambs were transported to West Virginia University’s Animal Science Farm and fed using a Growsafe™. Lambs were provided a complete pellet (16% CP) ad libitum while individual intake was measured. Half of the lambs from each sire FEC EBV type were infected with 5,000 H.C. L3 larvae and observed for 6 weeks alongside uninfected contemporaries. Artificial H.C. infection resulted in lambs becoming moderately infected with FEC ranging from (0 – 1208 eggs/g). RFI was calculated as the difference between actual and expected intake. Expected intake was predicted based on average daily gain and metabolic body size. Intake was not affected by sire FEC EBV type or infection status (P &amp;gt; 0.10). Infection status did not affect F:G, however HighFEC lambs tended to have greater F:G values (13.5 vs. 6.8 kg feed:kg gain; P = 0.07). RFI was not affected by sire FEC EBV type or infection status (P &amp;gt; 0.10). Individual sire (n = 9) had a significant effect on intake and RFI (P &amp;lt; 0.05). Year and year x sire interaction did not have an effect on RFI or F:G (P &amp;gt; 0.40). Sire FEC EBV type and infection status did not impact feed efficiency. However, variation between sires independent of year indicates potential sire impact on progeny feed efficiency in sheep.

122 Evaluation of Sire FEC EBV Type andHaemonchus contortous Infection on Feed Efficiency in Katahdin Sheep