SUSCEPTIBILITY OF 2 CROSSBREEDS OF SHEEP TO HAEMONCHUS-CONTORTUS

Studies were conducted on 20 crossbred lambs of 4-5 months old. Ten la mbs were Nali x, Corriedale cross (Hisardale) and the other 10 were Na li x Lohi cross (Munjal). Seven lambs each of both crossbreeds were in fected with 10,000 infective larvae of Haemonchus contortus. Three lam bs of each crossbreed served as uninfected controls. Clinicopathologic al examinations were done before and after infection and all the lambs were necropsied 28 days post-infection. The body weight gain, haemogl obin and packed cell volume were significantly lower in Hisardale lamb s and the peripheral eosinophil count was significantly higher in Munj al lambs. Significant hypoalbuminaemia and hypoglobulinaemia, a sharp increase in albumin: globulin ratio; significantly higher faecal egg c ounts; adult worm counts; abomasal pH, volume, congestion and oedema w ere observed in Hisardale lambs as compared to Munjal lambs. Clinical signs of haemonchosis were more severe in Hisardale lambs and two of t hem died. Munjal lambs therefore seem less susceptible than Hisardale lambs to H. contortus infection.