Effects of breed of hair sheep ram lambs on performance in a centralized test including artificial infection with Haemonchus contortus

Twelve Dorper (D; 4.5 ± 0.44 mo, 31.9 ± 1.75 kg), 18 Katahdin (K; 3.8 mo, 24.3 ± 0.76 kg), and 12 St. Croix (C; 4.5 ± 0.17 mo, 19.7 ± 0.99 kg) ram lambs were used in the first year of a centralized test for growth performance and response to artificial infection with Haemonchus contortus. Rams were randomly selected from 3 commercial farms in Missouri and Oklahoma. The confinement test at Langston University entailed an adjustment period of 2 wk followed by 8 wk of data collection. Breeds were housed separately in adjacent pens with automated feeders allowing free-choice access to a 15% CP (DM) and 50% concentrate pelletized diet. During adaptation, anthelmintic treatment resulted in low fecal egg count (FEC; 0.05) among breeds. Rams were categorized into 3 groups within breeds based primarily on MFEC and MPCV (High, Medium, and Low resistance) using the cubic clustering criterion of SAS, which resulted in unbalanced numbers in the groups (5, 5, and 2 for D, 12, 5, and 1 for K, and 8, 1, and 3 for C, respectively). Group means were similar (P > 0.05) in ADG, DMI, and RFI but varied (P