Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 16, 2001
Publication Date: February 1, 2002
Citation: BURKE, J.M. 2002. ARE DORPER CROSSBRED EWES AS TOLERANT TO INTESTINAL PARASITES AS ST. CROIX OR KATAHDIN EWES IN THE SOUTHEASTERN UNITED STATES? AMERICAN SOCIETY OF ANIMAL SCIENCE SOUTHERN SECTION MEETING. 80 (Suppl. 2)32. Technical Abstract: A study was conducted to evaluate tolerance to natural parasite infection in Dorper crossbred (DO), Katahdin (KA), and St. Croix (SC) ewes over a 17 month period. In Year 1 (May 2000 to December 2000) anthelmintic treatment of ewes occurred during wet, hot conditions in July and during late pregnancy in December. Breeds of yearling ewes included Dorper x Romanov x St. Croix (DO, n = 13), KA (n = 20), and SC (n = 15). Mature ewes (3 years of age; Dorper x Romanov, n = 15; SC, n = 9) were included after September 2000. In Year 2 (January 2001 to September 2001), ewes were treated with anthelmintic after fecal egg count (FEC) rose above 1000 eggs per gram (EPG) or after packed cell volume (PCV) fell below 20. Breeds evaluated were 3/4 or7/8 Dorper (DO; n = 17), Hampshire (HA; n = 19), KA (n = 24), and SC (n = 23). In both years, ewes were pastured together on tall fescue or bermudagrass overseeded with ryegrass and moved among pastures dependent on forage availability. In Year 1, FEC was greater and PCV was lower in July and August in DO ewes, but FEC was greater and PCV was lower in December and January in SC ewes (breed x time, P < 0.001). In Year 2, FEC were lower and PCV greater in April through July in DO ewes and these ewes were treated with anthelmintic two weeks later (August 3) than other breeds (July 20). The PCV was lowest for HA ewes for most of March through September compared with the hair breeds (breed x time, P < 0.001). Ewes were in good or excellent condition (body condition score of 3 to 4 out of 5) throughout the study. Parasite tolerance of Dorper crossbred ewes was comparable to that of Katahdin and St. Croix ewes and superior to that of Hampshire ewes when the biological challenge was moderate.