Growth performance and resistance to internal parasitism of small ruminant males from the south-central US in a centralized test

Performance of young male sheep and goats from different farms and of various breeds was determined in a centralized test at Langston University (LU), which included artificial infection with Haemonchus contortus. Year 1 included 2 Katahdin flocks (KS-A, n = 17, 3.5 mo of age, 35 kg; KS-B, 18, 4.0 mo, 19 kg), 20 Dorper (DS; 8.2 mo, 45 kg), 13 St. Croix (CS; 4.4 mo, 21 kg), 2 Boer herds (BG-A; 16, 3.8 mo, 21 kg; BG-B, 17, 19 kg) 16 Kiko (KG; 3.1 mo, 20 kg), and 14 Spanish (SG; 4.4 mo, 19 kg). In year 2, animals were progeny from breeding groups classified in year 1 as of high and moderate resistance, with 15 DS (3.8 mo, 29 kg), 14 CS (3.9 mo, 18 kg), 14 KG (4.0 mo, 19 kg), 13 BG-A (3.2 mo, 22 kg), and 17 SG (3.1 mo, 18 kg). Thus, the test included males from 8 flocks/herds, 6 commercial farms in AR, KS, MO, and OK and 2 herds of LU (i.e., B-A and S). There was 2 wk for adaptation and an 8-wk test period, with automated feeders allowing free-choice access to a 50% concentrate pelletized diet. During adaptation, anthelmintic treatment resulted in low fecal egg count (FEC; 0.05) for ADG and ADG:DMI in both years. In conclusion, based on FEC after an artificial challenge with H. contortus larvae in a standardized environment, there was considerable variability among flocks/herds of small ruminants in resistance to internal parasitism due to multiple factors such as species, breed, and genetic differences within breed.