Post-weaning fecal egg count estimated breeding value is associated with greater antibody production after clostridial vaccination in Katahdin lambs

Abstract

Previous work demonstrated that, Katahdin lamb survivability to weaning was affected by post-weaning fecal egg count (PFEC) estimated breeding values (EBV) and favored Low-PFEC lambs. Therefore, selection for PFEC is hypothesized to improve generalized immunity beyond resistance to parasitic infection. This study aimed to compare the effect of PFEC EBV on antibody production of Katahdin lambs in response to Clostridium perfringens type C&D and tetanus toxoid (CD&T) and C. perfringens type A vaccination. Lambs were grouped by their PFEC value into Low-PFEC (PFEC less than −50), Mid-PFEC (PFEC between −50 and +50), and High-PFEC (PFEC greater than +50). Prior to weaning and continuing 5 weeks after weaning, lambs were exposed to natural helminth infection on pasture and fecal samples were collected bi-weekly. Lamb FEC corresponded to genotype (950 epg High-PFEC vs. 452 epg Low-PFEC; P = <0.0001) over the course of the experiment. Three weeks prior to weaning lambs were vaccinated for CD&T and C. perfringens type A and again four weeks later. Serum samples were taken weekly for 8 weeks. Averaged across time, there was a stepwise decrease in immunoglobin (IgG) from Low-PFEC to High-PFEC groups (905 µg/mL, 739 µg/mL, and 644 µg/mL respectively; P < 0.0001). Upon booster vaccination IgG response was higher in Low-PFEC and Mid-PFEC groups than the High-PFEC group (2246 µg/mL, 2103 µg/mL vs. 1431 µg/mL, P < 0.0001). A moderate negative correlation was found between average serum IgG and lamb PFEC EBV (r = −0.55, P < 0.0001). Interestingly when PFEC values are less than − 50 or greater than + 50 lambs produce high or low IgG respectively. Collectively these data indicate that parasite resistant Katahdin lambs generate greater antibody response to clostridial vaccination.