MVSc

Representative population comprising 74 heads of Vechur and 108 numbers of crossbred cattle of Kerala were investigated for leptin gene polymorphisms and their associations with milk production traits. LEP/BspE1 and BM1500 are the polymorphic markers used for PCR-RFLP and microsatellite analysis, respectively.

For PCR-RFLP analysis, the amplified PCR product was digested with restriction enzyme BspE1 which revealed three genotypes in Vechur (CC, CT and TT) and two in crossbred cattle (CC and CT) indicating the presence of C (75 bp and 19 bp fragments) and T (94 bp fragment) alleles. The C/T allele frequencies were 0.82/0.18 and 0.89/0.11, respectively in Vechur and crossbred cattle. The genotypes of LEP/BspE1 polymorphism were distributed according to Hardy-Weinberg equilibrium with frequencies 0.71 (CC), 0.24 (CT) and 0.05 (TT) in Vechur and 0.79 (CC) and 0.21 (CT) with the absence of TT genotype in crossbred cattle under study.

The microsatellite polymorphism at BM1500 locus was analyzed in Vechur and crossbred cattle and two novel alleles of size 126 and 132 bp were detected. Allele frequency was highest for 132 bp and in Vechur (0.40) as well as crossbred cattle (0.46) under study. The polymorphic information content of BM1500 marker in Vechur was 0.6595 while 0.656 in crossbred cattle.

In the present study, the significant influence of LEP/BspE1 polymorphism on milk production traits. The T allele bearing Vechur and crossbred cattle showed 13.08% (89.77 kg) and 10.7% (466.63 kg) increase for 305 day milk yield, respectively whereas 9.96% (0.31 kg) and 8.38% (1.22 kg), respectively for average daily milk yield. A nonsignificant reduction for milk fat percentage was also observed associated with T allele in both populations. Increased body fat reserves, adipose tissue reserves, feed intake and favorable change in partitioning of nutrients in T allele possessing animals might have contributed to increased milk yield in cattle.

For BM1500 marker, highest averages of 305 day milk yield and daily milk yield were observed for Vechur and crossbred cattle possessing 136 bp allele. The highest milk fat percentages were recorded in 136 bp allele bearing Vechur animals and crossbreds possessing 138 bp allele. The association of BM1500 marker with milk production traits can be established only by expanding the research to an extensive cattle population.

The selection of Vechur and crossbred cattle, heterozygous for C and T alleles for LEP/BspE1 polymorphism can significantly improve milk yield. The use of molecular techniques provides new opportunities and challenges for building and using more accurately predictive and efficient selection procedures for livestock improvement.