Animal Science Abstract
Genetic parameters for direct and maternal effects on body weights of Muzaffarnagari sheep
A. Mandal1,A, F. W. C. Neser2, P.K. Rout1, R. Roy1 and D.R. Notter3
AE-mail: ajoymandal@rediffmail.com
1Genetics and Breeding Division, Central Institute for Research on Goats, Makhdoom, Mathura-281 122, Uttar Pradesh, India2Department of Animal Wildlife and Grassland Sciences, Faculty of Natural and Agriculture Sciences, Bloemfontein, South Africa
3Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306, USA
Abstract
Estimates of co(variance) components were obtained for weights at birth, weaning and 6, 9 and 12 months of age in Muzaffarnagari sheep maintained at the Central Institute for Research on Goats, Makhdoom, Mathura, India, over a period of 28 years (1976 to 2003). Records of 5530 lambs out of 169 rams and 1631 ewes were used for the study. Analyses were carried out by restricted maximum likelihood (REML), fitting six animal models, including various combinations of maternal effects. Heritability estimates for weight at birth, weaning and 6, 9 and 12 months of age were 0.09, 0.21, 0.06, 0.10 and 0.14, respectively. Maternal heritability of body weight declined from 0.07 at birth to 0.02 at weaning. The maternal permanent environmental component contributed 11% to the total variance for all traits except weight at 12 months. A significant large negative genetic correlation was observed between direct and maternal genetic effects on weaning weight, suggesting the presence of antagonistic environmental, as well as perhaps genetic, effects in daughter and dam. Results suggest that maternal additive effects were only important in early stages of growth, whereas a permanent environmental maternal effect existed at all ages up to 9 months, probably as a carry-over effect of maternal influences present at weaning. Modest rates of genetic progress appear possible for all weights, but the presence of an antagonism between direct and maternal effects on weaning weight would complicate attempts to improve both by selection.
Keywords: body weight, genetic parameters, maternal effects, Muzaffarnagari, sheep.
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