The progenies of Avikalin (Rambouillet × Malpura) breed born during 2004–06 (spring season) were evaluated for faecal egg count at naive and exposed stage of natural infection (predominantly Haemonchus contortus) and two divergent lines were created by selecting progenies from sires with low (R line) and high (S line) mean faecal egg count (FEC). The heritability estimate of log transformed FEC at naïve and exposed stage of natural infection was 0.223%±0. 194 and 0.114±0.112, respectively revealing existence of genetic variation for both innate and acquired resistance to infection. The performance of selected animals from both the lines was compared over the years and no untoward effects on different performance traits were observed. The trends in intensity of infection from R line revealed reduced FEC and increased ability of sheep to withstand infection and maintain productivity even in the face of prolonged worm challenge even without drenching. Results reveal that resistance to H. contortus is moderately inheritable and selection for resistance is possible and will not adversely affect production parameters in semi-arid environment.
Sheep, Haemonchus contortus, Disease resistance, Faecal egg count
