366 - Impact of Haemonchus Contortus on Feed Intake in Katahdin Sheep Selected for Parasite Resistance

Haemonchus contortous (Hc) infections have decreased profitability of flocks worldwide through loss of production efficiency and in severe cases death. Countless research efforts have been made in order to further understand the extensive impact of this gastrointestinal nematode (GIN). Quantifying the impact feeding behavior after Hc infection may prove vital, in understanding internal effect on growing lambs. The aim of this study was to evaluate Katahdin lambs with extensive genetic evaluation for feed efficiency and behavior utilizing a Growsafe™ system. Katahdin ewes from the Virginia Tech Southwest Agriculture Research and Extension Center in Glade Springs Virginia were divergently selected based on fecal egg count (FEC) EBV and mated to rams (n = 8) of similar genotype. A subset of lambs was selected for feedlot evaluation and transported to West Virginia University. Lambs were fed a complete pellet (16% CP) ad libitum while individual intake was measured in pen-fed groups with a GrowSafe™ system. Half of the lambs from each sire FEC EBV group were infected with 5,000 Hc L3 larvae and observed for 6 weeks alongside uninfected contemporaries. Artificial Hc infection resulted in lambs becoming modestly infected with FEC peaking in week 5 at 324 eggs/g. Infection level was not significant between all 4 groups (P < 0.05). Lambs administered H.C. had observably lower feed intake 2 days after infection. Both infected groups returned to normal intake with their control groups shortly after. Feed intake dropped again at day 10 and remained low until day 16 for LoFEC sired lambs and day 20 for HiFEC sired lambs. Offspring of low FEC rams exhibited an ability to return to normal intake levels earlier than lambs with high FEC EBV sires. Further analysis is needed with greater levels of parasite infection to confirm negative FEC EBV have a shorter duration of lower feed intake.