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123 Selection for Post-weaning Fecal Egg Count Estimated Breeding Value Is Associated with Greater Antibody Production After Clostridial Vaccination in Katahdin Sheep


 In a previous study, Katahdin lamb survivability to weaning was affected by sire post-weaning fecal egg count estimated breeding values (PFEC EBV) where lambs sired by low PFEC rams had greater survivability than high-PFEC-sired lambs. Therefore, selection for PFEC may also select for improved generalized immunity. The aim of this study was to compare effects of divergent PFEC mating on antibody production in purebred Katahdin lambs in response to vaccination. Katahdin dams with a PFEC value of greater than zero were bred to positive (high-PFEC) FECEBV rams, likewise, dams with a PFEC value of less than zero were bred to negative (low-PFEC) FECEBV rams. All lambs were managed as one cohort until approximately 105 days of age. During this time on pasture, a natural helminth infection was established, blood samples were taken weekly, and fecal samples were collected bi-weekly. Lamb FEC corresponded to sire/dam genotype (943 epg high-PFEC vs. 455 epg low-PFEC; P < 0.001). Serum samples were taken weekly for 3 wks after initial vaccination for Clostridium perfringens type C&D and C. perfringens type A and for 4 wks after booster vaccination, which occurred 3 wk following primary vaccination. Total circulating IgG was measured used an ovine-specific enzyme-linked immunosorbent assay (ELISA). To evaluate lamb IgG differences, data were analyzed using the General Linear Model (GLM) procedure of SAS with fixed effects of genotype, time, and genotype X time interactions. Means comparisons were performed on LS means of fixed affects or interactions, using Bonferroni adjustment. A genotype by time interaction revealed that IgG response to boostering favored LoPFEC lambs (1679.91 vs 1153.08 ug/mL, respectively; P < 0.001). When averaged across time, LoPFEC lambs generated greater IgG concentration than HiPFEC lambs (886.79 ug/mL vs 465.15 ug/mL, respectively; P < 0.001). These data indicate that PFEC breeding values in Katahdin sheep may predict immunological fitness outside the context of parasitic infections and has implications for use in selection of individuals less prone to disease.