Evaluation of resistance to gastrointestinal helminth nematodes in two naturally infected indigenous Nigerian goat breeds

Tropical goat breeds often have at least modest resistance to gastrointestinal nematode parasites (GIN), but enhancement of GIN resistance is important for breed improvement. This study compared changes in fecal egg count (FEC), packed cell volume, and body weight in Red Sokoto (RS) and Sahelian (SH) male and female weaner kids and adult goats. The RS is found throughout Nigeria, but the SH is found only in the arid Sahel. Goats were evaluated fortnightly for 20 times (MT) under normal grazing conditions and natural GIN infection over 9.5 months, beginning in the dry season (November) and ending at the end of the subsequent wet season (August). Animals were dewormed at the start of the study and during the rainy season (MT 18). Breed differences in FEC and PCV were not observed in weaners. Weaner females had lower FEC than males but were rapidly re-infected after deworming, perhaps in association with attainment of puberty. Adult SH goats of both sexes had lower FEC than RS goats in MT 8 through 17, suggesting a stronger acquired immune response. The FEC in lactating females of both breeds increased rapidly after deworming, to ≥ 3000 eggs per gram of feces at MT 19 and 20. The optimal time to evaluate GIN resistance in weaners was during the early rainy season, but the decision to focus on the initial high FEC near MT 15 or wait until mobilization of the acquired immune response near MT 17 requires further consideration.