RESISTANCE OF 4 SHEEP BREEDS TO NATURAL AND SUBSEQUENT ARTIFICIAL HAEMONCHUS-CONTORTUS INFECTION

The response of Red Maasai sheep to natural and artificial Haemonchus contortus infections was compared with sheep of Blackheaded Somali, Do rper and Romney Marsh breeds. Significant breed differences in egg cou nt, packed cell volume (PCV), and mortality rates showed that the Red Maasai sheep were more resistant to natural H. contortus infection tha n sheep from the other three breeds. Of the initial groups of 15 wethe rs of each breed, two animals from each of the Dorper and Blackheaded Somali groups and nine from the Romney Marsh group died with haemoncho sis during a 12 month field study. Following artificial infection of t he Red Maasai, Dorpers and Blackheaded Somalis, with 10000 H. contortu s L3, the Red Maasai sheep maintained a lower egg output and a higher PCV than animals of the other two breeds. The results clearly showed t hat breed substitution with the Red Maasai is a control option in area s where sheep are kept for meat and H. contortus is endemic. (C) 1997 Elsevier Science B.V.