Impact of Haemonchus contortus on feed efficiency and feeding behavior of Katahdin and Suffolk lambs

Abstract

Nutritional impact of internal parasitism, specifically Haemonchus contortus (Hc), is a significant contributor to production losses in small ruminants. Both chronic and subclinical infections generate millions of dollars of losses worldwide. Understanding the nutritional impact of Hc on lamb performance is crucial in determining the additional nutrient requirements of infected individuals. The aim of this study was to evaluate nutritional impact of Hc on infected Katahdin lambs with extensive genetic selection for parasite resistance and susceptible Suffolk lambs. Growth, feeding behavior, and feed efficiency (RFI. F:G) were evaluated during artificial Hc infection. Katahdin ewes from the Virginia Tech Southwest Agriculture Research and Extension Center in Glade Spring, Virginia were mated to rams (n=8) selected for parasite resistance genotype (PFEC EBV). A subset of lambs was selected for evaluation in a feedlot environment and transported to West Virginia University’s Animal Science Farm in Year 1 (Y1) and Year 2 (Y2). Purebred Suffolk lambs were selected from the West Virginia University flock and reared in parasite free conditions (n = 9). Additional lambs were sourced from purebred Suffolk flocks in West Virginia and had parasite exposure while reared on pasture (n = 31). Lambs sourced from outside flocks were transported to West Virginia University’s Animal Science Farm, acclimated to feed, and monitored for FEC. All lambs were fed a complete pellet (16% CP) ad libitum while individual intake was measured with a modified GrowSafe™ system. Half of the Katahdin lambs from each sire PFEC EBV group were infected with 5,000 Hc L3 larvae and observed for 5 weeks in Y1 and 6 weeks in Y2 alongside uninfected contemporaries. Artificial Hc infection resulted in lambs becoming moderately infected with FEC ranging from (0 – 1208 eggs/g). Half of the Suffolk lambs (n=20) were artificially infected with 5,000 Hc L3 larvae in a 5wk primary and 5wk secondary infection with a 2wk rest period in between. Artificial infections were significant (P < 0.05) between infected and uninfected lambs in all experimentation excluding the Suffolk secondary infection (P = 0.71). Infection intensity measured by PCV remained moderate with values remaining above level of concern. Feed efficiency measured in all feeding trials was measured by RFI and F:G. Differences in feed efficiency was not detected between infection status; however, sire was a significant factor affecting feed efficiency of Katahdin progeny (P < 0.01). Feeding behavior was measured for both duration and frequency during infection in all