Comparison of various models for the estimation of heritability and breeding values.

The exploration of additive genetic variance for the selection of animals is the central paradigm in quantitative genetics and it is important to use appropriate animal models considering important factors. This study compares various factor effects for heritability and breeding values estimations on data collected on the Corriedale. Overall, the heritability estimates were the highest for birthweight (BW). Both the additive genetic variance and the heritability values were reduced upon adding more random effects. Year-effect as random reduced the heritability except for BW. The highest average accuracy for breeding values for birth, weaning, 6, 9, and 12-month-weights for were 0.656, 0.567, 0.519, 0.486, and 0.515. These were observed for models having sex or sex and parity as fixed effects. It is concluded that fixed and random factors have a significant impact on genetic-factors and breeding-value accuracies and should be considered during selection programs and make the selection program more effective.

Polymorphism study of growth differentiation factor 9B (GDF9B) gene and its association with reproductive traits in sheep.

GDF9B protein plays a critical role in growth and differentiation of early ovarian follicles. In Inverdale and Hanna sheep, mutations in exon-2 of GDF9B gene have been recorded to show increased ovulation rate in heterozygous condition whereas homozygotes are infertile. Present screen study was carried out to explore the presence of these reported mutations in Corriedale and Local Kashmir Valley sheep with high rate of twinning. Exon-2 of GDF9B gene was amplified and the polymorphism was explored by SSCP technique. In the process three different bandings were observed. Later on these patterns corresponded with three different allelic forms on nucleotide sequencing. Phylogenetic analysis revealed that the nucleotide sequences of alleles observed in the present study and that of a published sequence of sheep were having the same point of origin. The results were also compared with goats, large ruminants and humans. The allelic frequencies of allele A and B were 0.64 and 0.36, respectively in Corriedale sheep whereas the allelic frequencies of all the three alleles in Kashmir Valley sheep were 0.60, 0.34 and 0.06. SNP "C" of the designated genotype AC was observed to pronounce a significant effect on litter size with average litter size going up by 0.63 as compared with the nearest genotype AB wherein the litter size was 1.29±0.05. The average litter size between AA and AB genotypes did not vary significantly.