Estimates of genetic parameters for faecal egg count of Haemonchus contortus infection and relationship with growth traits in Avikalin sheep.

Genetic parameters for faecal egg count were estimated in naturally challenged Avikalin sheep developed and maintained at Central Sheep & Wool Research Institute, Avikanagar, India, over a period of 4 years (2004-2007). The data on faecal egg count for 433 animals descended from 41 sires, and 151 dams were used for the study. Genetic analyses were carried out using restricted maximum likelihood, fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Direct heritability for the trait was 0.149 +/- 0.096 when maternal effects were ignored. In the model which takes in to account direct genetic, maternal genetic and maternal permanent environment effect together, it was observed that maternal heritability (m(2)) accounts for 0.6% of total variation whereas maternal permanent environmental effect (c(2)) accounts for 6.14% of total phenotypic variation. Effect of faecal egg count on the growth characteristics was observed to be significant. It was seen that wherever FEC was high, body weight or average daily gain declined in active infective stage. After termination of the infection, these effects were found to be non-significant. Result suggests that direct genetic and maternal permanent environmental effects were important for this trait; thus, they need to be considered for improvement in the trait.