Optimal pre-weaning body weight as an early selection criterion for improving meat production in barki sheep

Abstract EN

The present study was initiated to investigate the importance of pre-weaning body weights in selection of Barki lambs.

Four criteria were proposed to judge these pre-weaning body weights in order to assign the optimal one of them to be taken as an early selection criterion for improving meat production in Barki sheep.

Pre-weaning body weight records and pedigree information of 2942 Barki lamb progenies of 186 sires and 1653 ewes belonging to the sheep flock of the Desert Research Centre raised in two research stations; Ras Elhekma (from 1963 to 1972) and Maryout (from 1973 to 2004) were used in the present study.

The current study dealt with the lamb pre-weaning body weights from birth and at biweekly intervals till weaning at 120 days together with two adult body weights at 360 days and at 480 days.

Data were analyzed by fitting a direct-maternal animal model using the MTDFREML program to estimate (co)variance components as well as direct and maternal heritabilities, correlations and breeding values for the studied traits.

Maternal heritabilities were higher than the corresponding direct ones from birth till the age of 30 days, and then turned to be lower for body weight at 45 days and up to weaning.

Similar trends were revealed for maternal genetic variances and maternal breeding values compared with the corresponding direct ones.

The estimated genetic correlations (either direct or maternal) were generally high and positive.

The present study showed that body weight at 90 days, W90, as the "optimal" selection criterion to improve meat production in Barki sheep since it generally satisfies most of the criteria suggested to determine that optimal body weight.

Compared with the other pre-weaning body weights, W90 had generally higher heritability and breeding values.

W90 had also higher utility in predicting adult body weights through high and positive direct and maternal genetic and environmental correlations.

Higher genetic, phenotypic and environmental variation occurred in W90.

There is no antagonism relationship between direct and maternal effects existed for W90 and between this trait and adult body weights.

Therefore, it is anticipated that higher genetic response would be attained if the selection based on W90.

Accordingly, the present study recommends W90 as the optimal early selection criterion for breeding purposes aiming at genetic improvement for meat production in Barki sheep.