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ThesisItem Open Access Evaluation and comparison of polymorphism of beta casein gene in vechur and crossbred cattle of Kerala(Department of Animal Breeding, Genetics and Biostatistics, College of Veterinary and Animal Sciences, Mannuthy, 2010) Muhammed, E M; KAU; Stephen MathewBeta casein (β-CN) is the major milk protein which imparts biological, technological and physical properties to the milk. Recently, the polymorphism of the gene at codon 67 has attracted much public health attention. A single nucleotide polymorphism (SNP) from CCT to CAT leads to an amino acid change in the mature protein from proline to histidine. Among the twelve β-CN variants identified A1 and A2 are the common types and others are very rare. A1 variant has histidine at position 67 of the amino acid sequence while A2 possess proline at this position. This single amino acid change causes the release of bioactive peptides upon gastro intestinal digestion. Morphine like opioid beta casomorphine-7 (BCM-7) thus released from A1 milk is reported to cause various illness like diabetes mellitus, heart diseases, atherosclerosis, schizophrenia and sudden infant death syndrome (SIDS). The original variant A2 does not produce BCM-7 and thus is safe for human consumption. The major taurine milch breeds such as Holstein Friesian and Ayrshire have a high frequency of A1 allele where as Channel Island breeds such as Guernsey and Jersey have more of A2 allele. It is also interesting to note that most of the Indian breeds of animals have only β-CN A2 allele. The present study was undertaken to characterise the β-CN gene polymorphism in Vechur and crossbred cattle of Kerala considering its public health importance. Blood samples were collected from 72 Vechur cattle, and 14 Kasargode Dwarf cattle available in the KAU farm and 100 crossbred cattle randomly selected from different parts of Kerala. Genomic DNA was isolated by standard phenol chloroform procedure. Beta casein A1 A2 polymorphism was analysed by Allele Specific Polymerase Chain Reaction (AS-PCR). The genotypic frequencies of A1A1, A1A2 and A2A2 were, respectively, 0, 0.40 and 0.60 in Vechur cattle, 0.32, 0.28 and 0.40 in crossbred cattle and 0, 0.79 and 0.21 in Kasargode cattle. Genotypic frequencies were not found to be in Hardy-Weinberg equilibrium in crossbred cattle while in Vechur and Kasargode cattle frequencies were found to be in equilibrium. The A1 and A2 allele frequency was 0.20 and 0.80 in Vechur cattle, 0.46 and 0.54 in crossbred cattle and 0.39 and 0.61 in Kasargode cattle. Comparison of allele frequencies revealed that there is significant variation in allele frequencies among these three groups of animals. The relationship between β-CN A1/A2 polymorphism with milk yield was also assessed. The average daily milk yield was 1.27±0.05 kg in Vechur cattle. The peak yield of crossbred cattle was 10.71±1.046 kg. The average daily milk yield for A1A2 genotype in Vechur cattle was 1.52±0.08 kg and 1.14±0.04 kg for A1A2 genotype. The t-test showed the difference in the milk yield of the two genotypes was significantly different at 5% level of significance. In crossbred cattle the peak yield (kg) of A1A1 genotype was 14.64±3.181, 8.54±0.194 for A1A2 genotype and 9.09±0.125 for A2A2 genotype. The A1A1 genotype in crossbred cattle showed significantly higher average peak yield compared to other genotypes and difference between A1A2 and A2A2 genotypes were not significantly different. From the present study it can be concluded that selection for enhancing milk production may increase the frequency of harmful A1 allele in our bovine population. So efforts should be taken to enhance the A2 allele with a view of transforming our cattle population capable of producing A2 variant of β-CN which has a global demand. The information generated in this study on the genotypes of Vechur and Kasargode dwarf cattle can be very effectively used for developing a herd/breed of cattle with A2A2 β-CN genotype.