Exploring the genetic resistance to natural gastrointestinal nematode infection in Indian goats.

The present study investigated the genetic component of host resistance to gastrointestinal nematode infections in two goat breeds in a semi-arid climatic region of India. The study was carried out on 888 animals belonging to two goat breeds. Live weight, faecal egg counts (FEC) and packed cell volume (PCV) following natural parasite challenge were measured at 3, 6, 9 and 12 months of age over a 3-year period. Pedigree relationships between goats extending back 3 generations were available. The study estimated the heritabilities of indicator traits (FEC and PCV) in goats and also quantified relationships between indicator traits and growth traits at the genetic, phenotypic and environmental level. It also provided an insight for the inclusion of genetic information on resistance to nematode infection into breeding programmes. The heritabilities of the indicator traits were low to moderate in this population. Genetic correlations between FEC at 6, 9 and 12 months of age were strong (approaching unity) indicating that the trait may be controlled by same genes at these different ages. The genetic correlation between FEC and PCV from 6 months of age onwards was negative and moderate to strong. Correlations between FEC and growth traits tended to be negative. Selection index modeling investigated the use of FEC, PCV and bodyweight in selection schemes. Selection based on the measurements at 9 months of age was proposed as a means of improving productivity as well as reducing pasture contamination, thereby enhancing sustainable livestock production.