(Posted on 8 January 2011)
About one third of the milk proteins are beta caseins and their breakdown on digestion create different biological activities. And A1 and A2 are the prominent types of Beta caseins of which A2 is thought to be the original Beta casein produced by the ancestors of the present day dairy cattle. The studies worldwide have shown that A2 Beta casein rich milk is likely to reduce the risk of heart disease and Type 1 childhood diabetes. It is also believed that the digestion of A2 Beta caseins does not produce proteins linked to worsening of autism symptoms.
The researches on the benefactor of A2 Beta caseins are still going on. Beta casein A2 –a milk protein that is believed to prevent diabetes mellitus, heart diseases, atherosclerosis, autism and sudden infant death syndrome (SIDS) has been found in Vechur cattle. The study was conducted by Dr E.M. Muhammed at College of Veterinary and Animal Sciences, Mannuthy under the guidance of Dr Stephen Mathew, Professor, Department of Animal Breeding, Genetics and Biostatistics.
Beta casein (β-CN) is the major milk protein which imparts biological, technological and physical properties to the milk. The recent finding that Beta casein yields biologically active peptides upon gastrointestinal digestion, have attracted the attention of both public health authorities and animal breeders. 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 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. Beta casein A1 A2 polymorphism was analysed by Allele Specific Polymerase Chain Reaction (AS-PCR).
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.
The research findings of Dr.E.M.Mohammed (as part of his M.V.Sc thesis) that the milk of Vechur cattle is found to be rich in Beta casein A2 with its beneficial effects of preventing diabetes, heart diseases, atherosclerosis, autism and sudden infant death syndrome (SIDS), in comparison to the Kerala’s preferred and high yielding cross-bred Jersey, Holstein-Friesian and Brown Swiss cattle have drawn the attention of the researchers, academics and media quite recently.
According to Dr Mohammed, Milch breeds such as Holstein Friesian and Ayrshire have a high frequency of A1 gene but most of the Indian breeds have only the beneficial A2 gene. His comparative study on the presence of A2 Beta casein in Vechur cows and cross-bred cows revealed that cross bred cattle though yields more milk may be rich in harmful A1 gene. He is of the view that “our efforts should be to increase cattle population capable of producing milk with the beneficial A2 gene variant of beta casein which has a global demand.”
Dr Mohammed from Chelannur, Kozhikkod is pursuing his doctoral studies in Animal Breeding,Genetics and Biostatistics at Kerala Agricultural University on deputation from the Department of Animal Husbandry, Kerala.