MVSc

The present investigation was undertaken to identify the biochemical polymorphism at different milk protein loci and to establish their inheritance pattern in Malabari and its exotic cross viz., Alpine X Malabari. It was also envisaged to analyse the association of different milk protein variants with lactation milk yield. Hundred goats belonging to Malabari (50) and Alpine X Malabari (50) were typed for milk protein variants employing horizontal Polyacrylamide Gel Electrophoresis (PAGE). The milk protein loci studied were Alpha S1 casein, Alpha S2 casein, Beta casein, kappa casein and Beta lactoglobulin.
Two Alpha S1 casein variants, the faster Alpha S1 casein F and the slower Alpha S1 casein S with three phenotypes Alpha S1 casein AA, Alpha S1 casein AB, and Alpha S1 casein BB were observed. S allele had the frequency of 0.52 in Malabari and 0.70 in Alpine x Malabari crossbreds. The gene frequency of Alpha S1 casein F and Alpha S1 casein S were 0.48 and 0.52 in Malabari and 0.30 and 0.70 in Alpine X Malabari crossbreds, respectively. The frequency of S allele was higher in both the populations.
Alpha S2 casein locus exhibited three phenotypes viz., AA, AB abd BB controlled by two allels A and B. A allele had the higher frequency of 0.71 in Alpine x Malabari crossbreds compared to 0.62 in Malabari. Higher frequency of AA phenotype was found in Alpine x Malabari (0.52) and that of AB phenotype in Malabari (0.44).
Two alleles namely A and B contributed three phenotypes viz., AA, AB and BB at the beta casein locus in both the populations studied. Malabari showed higher frequency of B allele (0.55) while Alpine x Malabari had higher frequency of A allele (0.60). Beta casein AB phenotype had higher frequency in Malabari breed (0.54).
Kappa casein locus showed two alleles A and B contributing three phenotypes viz., AA, AB and BB. The frequency of A allele was higher in both the population. The phenotype AA was higher in Alpine X Malabari crossbreds (0.56) while Malabari had higher frequency of AB phenotype (0.48)
Two alleles namely A and B with three phenotypes AA, AB and BB were identified at Beta lactoglobulin locus. The phenotype AA was dominant in Alpine x Malabari crossbreds (0.50) and the frequency of BB phenotype was almost similar in both Malabari and Alpine x Malabari crossbreds (0.14 in Malabari and 0.12 in Alpine x Malabari crossbreds). The gene frequency of Beta lg A was found to be 0.65 in Malabari and 0.67 in Alpine x Malabari crossbreds.
Both the populations studied were in genetic equilibrium with respect to these milk five protein loci. No significant diversity was found to exist between genetic groups.
The genetic variability in the populations was calculated by estimating the heterozygosity. The overall heterozygosity in different populations indicated that the Malabari breed had comparatively higher degree of herozygosity (0.4711) followed by Alpine x Malabari crossbreds (0.4209). In Malabari maximum heterozygosity was observed at Alpha S1 casein loci (0.4992). In Alpine x Malabari maximum heterozygosity was observed at Beta casein locus (0.4800).
The study of association between the genes controlling synthesis of milk protein showed significant association between the Beta casein with the Beta lactoglobulin Bb types in Alpine x Malabari crossbreds. All the other combinations of genes did not show any significant association.
Milk protein variants were not found to be associated with the lactational yield (120 days) of the goats.
The present study could establish the existence of biochemical polymorphism at Alpha S1 casein, Alpha S2 casein, Beta casein, Kappa casein and Beta lactoglobulin loci in Malabari and Alpine x Malabari crossbreds studied.