Evaluation of lactation milk yield and polymorphism of alpha-lactalabumin gene in crossbred cattle of kerala

Abstract

The present study was carried out to assess the milk yield of crossbred cattle of Kerala by studying four different zones of the state viz. northern, southern, central and highlands and to analyse the association of α-lactalbumin gene polymorphism with milk production of crossbred cattle in Kerala. One day milk yield of 500 animals from each zone, at a lactation stage of 7-13 fortnights after calving was recorded. From this one-day milk yield 305-day milk yield of crossbred cattle was predicted using the formulae given by Iype (1991). The predicted lactation milk yield was used for estimating average milk yield of crossbred cattle in Kerala. The overall least squares mean of 305-day milk yield was 2351 ± 28.9 kg. Least squares analysis of variance has shown that different zones and parity exerted significant effect on 305-day milk yield (P ≤ 0.05). The highest least squares means for 305-day milk yield was in southern zone and the lowest was in central zone. The least squares mean for 305-day milk yield according to parity was highest in second parity, followed by third parity and the lowest was in fifth parity. Genomic DNA samples isolated from 25 crossbred cows selected at random from each zone was subjected for PCR-RFLP of α-lactalbumin gene at two different specific loci. On successful amplification the expected 166 bp and 429 bp fragments were obtained. Digestion of 166 bp amplified product with Mnl1 enzyme revealed similar pattern of digestion for all animals studied, indicating the absence of α-LA/Mnl1 (+) in the population. Restriction of 429 bp amplified product with Bsp12861 enzyme revealed two digestion patterns (indicating the presence of two α-LA/Bsp12861 alleles). The gene frequencies of α-LA/Bsp12861 (+) and (-) alleles were 0.08 and 0.92 respectively. In the crossbred population studied, none of the animal showed α-LA/Bsp12861 (+/+) genotype. The average milk yield of 79 α-LA/Bsp12861 (+/+) genotypes was 2779 kg and that of 16 α-LA/Bsp12861 (+/+) genotypes was only 2364 kg. However, the difference was statistically non-significant. It is suggested to conduct further research in large samples to confirm the findings and to identify other polymorphic loci associated with milk yield.