Here is an example of why so many of us feel the Genomic possibilities are trivialized.
Molecular genetic issues beyond imputing PTA values face dairy cattle breeding, if we are to remain responsive to the concerns and desires of the millions of consumers who buy milk and milk products.
The Devil In The Milk is a book authored by Keith Woodford of University College, Co. Cork, Ireland.
This book is published for the US by the “Weston-Price Foundation” and is available from “Acres USA” which is a pro-organic farming organization that publishes monthly newsletters read by food activists.
The focus of this book is Dr Woodford’s review of the work of the A2 Corporation Ltd. (New Zealand) and related research from universities and agencies including the World Health Organization concerning the health properties of Beta Caseins -- proteins that represent 30% of milk’s total protein volume.
Basically, all lactating mammal species produce Beta Casein as one of the six forms of milk proteins. This particular casein is normally A2 exclusively—but in the bovine species, twelve variants have been identified (generally lumped together as A1) as a result of mutations at the CSN2 gene locus. The A2 Beta Casein is a repository of much of the health benefit that milk offers calves and humans. But as a result of the last twenty years of A2 vs. A1 research into cows’ milk, the A1 mutations are being linked to various auto-immune diseases, such as autism, juvenile diabetes, and heart disease. (The correlations in various researches indicate this link to be as strong as those found for smoking and lung cancer.)
History of the Beta Casein debate
In the 1980s, this possibility first surfaced as a result of work done in private research in New Zealand, by a man suffering from cancer looking for natural supports to immune function. His research was a two edged sword for the dairy industry—he affirmed (a) that milk was a useful support to rebuilding a human immune system ravaged by disease and cancer treatment regimens, but (b) only if that milk was produced by cows carrying the “normal” beta casein gene that matches other mammalian species.
In effect, his research challenged some milk as doing more harm than good, and this was alarming to the Fonterra (NZ) mega-milk cooperative that moved to challenge his conclusions. Frail health leading to an early death prevented further research and his papers were nearly forgotten—until picked up as worth a second, more exhaustive look in the 1990s (stimulated by rising levels of autism and diabetes in children as well as heart disease and obesity issues in wealthier nations consuming more dairy products). A variety of studies were done appearing to support those original conclusions (although the NZ Food Safety Authority in 2004, and the equivalent European body in 2009, recommended further research to confirm whether these links were “causal” or just “associative”).
Where the debate stands today
Quoting from the above government advisories: “As a matter of individual choice, people may wish to reduce or remove A1 beta casein from their diet (or their children’s diet) as a precautionary measure. This may be particularly relevant for those who have or are at risk of the diseases mentioned (type 1 diabetes, coronary heart disease, autism and schizophrenia). However, they should do so knowing that there is substantial uncertainty about the benefits of such an approach.”
Organic Valley Cooperative (CROPP) based in Wisconsin has been proactive in encouraging their dairy members to select in favor of homozygous A2 Beta Casein. The “Stoneyfield Yogurt” company would like to label all its organic yogurt products as produced from cows/herds known homozygous for A2.
How distributed is the A2 gene?
Guernseys are the gold standard—90% of all Guernseys tested carry A2. Jerseys are next at a 60% level. Holsteins are 50%; Brown Swiss 40%; the various non-Holstein “red” breeds 40% to 30%.
As a result of limited numbers tested, Lakenvelder (Dutch Belted) appear at least 50%. The key point is that it would be relatively easy for Jersey and Holstein dairymen to breed homozygous A2 herds, due to the 50+% distribution and the largest numbers of tested AI sires known as A2 carriers.
Homozygous vs. Heterozygous gene expression
For those with health concerns, aware of the A2 issue, only A2A2 cows’ milk is acceptable. Neither recessive (dual allele) or dominant (single allele) genes, Beta Casein inheritance is simple:
Genes in bull a+b: combines with Genes in cow c+d: the four pairing patterns possible are (a+c) (a+d) (b+c) (b+d)
A1-A1 bull x A1-A1 cow = 0% chance of an A2 calf: four possible combinations (A1A1) (A1A1) (A1A1) (A1A1)
A1-A2 bull x A1-A1 cow = 50% chance of an A2 calf: four possible combinations (A1A1) (A1A1) (A2A1) (A2A1)
A1-A2 bull x A1-A2 cow = 75% chance of an A2 calf: four possible combinations (A1A1) (A1A2) (A2A1) (A2A2)*
25% chance of a homozygous A2 calf *
A1-A2 bull x A2-A2 cow = 100% chance of an A2 calf four possible combinations (A1A2) (A1A2) (A2A2)* (A2A2)*
50% chance of a homozygous A2 calf*
A2-A2 bull x A2-A2 cow = 100% chance of a homozygous A2 calf*: combinations (A2A2)* (A2A2)* (A2A2)* (A2A2)*
Heterozygous A2 cows will produce both forms of the Beta Casein proteins. Homozygous A2A2 cows will only produce the A2 “normal” form of the Beta Casein proteins.
This has nothing to do with the Kappa Casein genes, which affect cheese yields (the B variant yields 15% more cheese than the A variant at the same level of protein % overall). But inheritance of K/C is identical in pattern to what is presented above for B/C.
How do I test my cows for Beta casein—and is it worth the effort?
It could be a question of how proactive you wish to be relative to trends in milk marketing. As food activism turns its sights on dairy (already evidenced by the data showing resurgent demand for organic milk which may reach 5% of total bottled milk sales in this decade) a demand for A2A2 milk could create a premium market that is independent of the organic market (for example, health practitioners recommending their patients seek source of A2A2 milk as a result of human genetic markers for the noted diseases). Is this just a fad? The overpromotion of margarine as a butter substitute for health reasons—mostly debunked in the latest research—has lasted our entire lifetimes.
Testing for Beta casein is costing around $30 per cow (or bull) and is usually done from a hair follicle sample (pull 20 or so clean hairs from the tail switch). Samples can be sent to UC-Davis, Veterinary Genetics laboratory, or to A2 Corporation (Taurus Service is providing a transmittal service for samples to A2 Corporation).
Once a base line distribution of the gene in your herd is known, use of only A1A2 and A2A2 sires will allow you to move quickly in an “all A2” direction without unduly limiting genetic selection choices on preferred traits. (Not all AI studs publish their A2 results, but most if not all are testing actively marketed sires, so the information is generally available upon request.) Effective mating programs that produce a surplus of heifers will allow a faster transition to “all A2” status if focusing cow sales on non A2 variant individuals.
The “Brave New World” of Molecular Genetics in future dairy gene selections
Genomic applications have dramatically altered how AI studs select young sires and market their total sire programs. 40% of Holstein and Jersey cows are now being mated with unproven sires based on Genomic imputed values.
But this only scratches the surface of what may come from this technology, actually of more direct benefit to dairymen—identifying gene traits for feed efficiency, cow health and milk quality.
Inside you will read of an area of molecular genetics that could create a new premium milk market opportunity. AI sires are now being tested for such gene possession as has drawn attention from health researchers and food activists.
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