Genetic and environmental influences on faecal nematode egg counts of Jamunapari goats in India

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Abstract

The present study was carried out from 1999 to 2003 to determine the genetic and environmental influences of faecal egg count (FEC), an indicator of host resistance, in adult Jamunapari goats with naturally acquired gastrointestinal nematode parasite infections (predominantly Haemonchus contortus). FEC data on 670 records of Jamunapari goats descended from 54 bucks and 208 does were used in this study. Analyses were carried out by restricted maximum likelihood estimation, fitting an animal model. Four different animal models ignoring or including maternal genetic or permanent environmental effects were fitted. Different environmental effects, that is, sampling year, month and the sex of the animals, significantly (P<0.01) influenced FECs in the goats. Direct heritability estimates were inflated substantially for this trait when maternal effects were ignored. The direct heritability estimates for the trait ranged from 0.11 to 0.16 depending on the model used. Low estimates of maternal heritability (m2=0.06) and the fraction of variance due to maternal permanent environmental effects (c2=0.09) for FECs were observed in the present study. The results suggest that direct and permanent environmental maternal effects were important for this trait; however, maternal additive effects had less impact on this trait. These results also indicate that modest rates of genetic progress appear possible for FECs.

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