Abstract :
Variance components and genetic parameters were obtained for pre-weaning average
daily body weight gains of Muzaffarnagari sheep maintained at the Central Institute for
Research on Goats, Makhdoom, Mathura, India, over a period of 17 years (1976–1983 and
1996–2004). In this study, the pre-weaning average daily gains (ADG) was considered in
six successive 15 day periods starting at birth and up to 90 days (ADG1–6). Records of 2930
lambs descended from 78 rams and 977 ewes were used in the study. Analyses were carried
out by restricted maximum likelihood (REML) fitting an animal model and ignoring
or including maternal genetic or permanent environmental effects. Six different animal
models were fitted for all traits for comparisons of models in this study. The best model
was chosen after testing the improvement of the log-likelihood values. Direct heritability
estimates were inflated for all traits when maternal effects were ignored. Direct heritabilities
estimates ranged from 0.01 to 0.26 for pre-weaning average daily weight gains in this
study. The permanent maternal environmental (c2) effects on average daily weight gains
during birth to 15 days (ADG1), 15–30 days (ADG2) and 30–45 days (ADG3) accounted for
5–17% of the total phenotypic variance in this breed. The very low to moderate heritability
estimates of pre-weaning daily weight gains in this study indicates that only slow genetic
progress may be possible for these traits from selection under the prevailing management
system. Results suggest that direct and permanent environmental maternal effects were
important for this trait; however, maternal additive effects had no impact on this trait.
