The protein structures in milk are called “caseins”. Each form is a result of the animal possessing a sequence of genes to produce it. “Kappa Casein” affects cheese curd formation (BB K/C is preferred for higher cheese yields)—“Beta Casein” affects immune function and how proteins act after ingestion.
Keith Woodford (an agricultural research professor at Lincoln University in New Zealand) wrote a book in 2007 titled Devil in the Milk—reviewed in “Acres USA”, promoted by the Weston Price Foundation - which linked one Beta Casein gene variant (A1) with a host of current health issues: heart and arterial disease, autism, type 1 diabetes, and schizophrenia. A1 variant is a mutation first found in Northern European and North American dairy cattle, while the A2 variant is still primary to Southern European, African and Asian cattle. (There are in fact 12 gene variants of Beta casein; only three of significant frequency. The original A2 variant is the basis for the wholesome reputation of “milk”. The fact of A1’s existence could destroy this hard-fought reputation, if promoted by vegan activists.)
The mutated fragment is called “beta casomorphin 7” which is a powerful opioid (narcotic) as well as an oxidant, and Dr Woodford’s book quotes over 100 research papers to assemble the evidence. BCM-7 is now associated with lactose intolerance and auto-immune diseases (type 1 diabetes is such a disease).
Distribution within breeds
Known dairy breeds vary in the proportion of A2 (“good”) to B (“OK”) to A1 (“bad”) alleles possessed.
Guernsey: (1991 study) 88% to 97% A2: 1% to 2% B: 1% to 6% A1 (USA cows)
Jersey: (1991) 49% to 52% A2: 29% to 37% B: 9% to 22% A1 (USA cows)
(1997) 59% A2: 29% B: 12% A1 (New Zealand)
(1990) 58% to 65% A2: 35% B: 7% A1 (Denmark)
Holstein: (1990-1991) 24% to 62% A2: 1% to 6% B: 31% to 66% A1 (USA)
(1997) 51% A2: 3% B: 46% A1 (New Zealand)
(1997) 47% to 60% A2: 2% to 10% B: 40% to 47% A1 (Europe)
Fleckveih: (1997) 56% to 63% A2: 15% B: 19% to 34% A1 (Germany)
Ayrshire: (1997) 49% to 53% A2: - - 43% to 51% A1 (Finland & NZ)
(1992) 28% to 40% A2: 1% B: 60% to 72% A1 (USA & UK)
Euro Red: (1997) 23% to 53% A2: 1% to 6% B: 46% to 71% A1 (Sweden et al)
Consequences of the distribution of Beta Casein knowledge
The organic dairy industry is rapidly embracing the A2 vs A1 Beta casein difference, as it provides an added basis for justification of a premium product price. Stoneyfield Yogurt and the Organic Valley marketing cooperative are both encouraging their supplier grazing farms to test their cows in preference for A2 carriers, and to breed accordingly, exclusively to A2A2 sires. (Some earlier research suggested that grass-based dairy nutrition programs enhance the production of the A2 Beta casein benefits.)
Testing your cows for the Beta casein gene markers is costly ($22-$30 per sample) but possible (the A2 Corporation of New Zealand has lab agents in Oregon and northern Michigan)—in perspective, it is less than the annual cost of entering a cow on DHIA for one year. Currently, the only AI system publishing Beta Casein markers on their sires is LIC New Zealand (available through us, distributed by Taurus in the USA) but we would anticipate other AI systems to test sires of interest as farm demand increases.
How hard is it to breed for A2 and away from A1 beta casein?
Until all AI sires are tested and their markers published, it will be difficult. The “safe” route is to focus on the LIC New Zealand sires (many of which were recently “aAa” analyzed) because you can select on known possession of A2A2. If you milk Guernseys you hardly have to worry—if you milk Jerseys, in two generations you could likely eliminate the A1 presence (only 7% to 22% frequency), as these gene variants are simple alleles (not dominant vs recessive) thus selecting in favor of one consistently reduces the other in frequency. If you milk Holsteins, it may take three or four generations because the level of A1 is three times as high as randomly distributed. (You will note that some of the worst A1 frequency is in the Euro Red breeds that have been popularized in crossbreeding.)
Cross breeding is no substitute for selection on the gene marker. Those whose milk production system and cattle marketing has been promoted on “grass adaptation” and “healthier crossbred cows” are not in any way prepared to claim milk product superiority under A2 vs A1. In this situation, it is your choices in sires—not choices in breeds—that will determine where you start, and how quickly you get where the market may influence you to go.
But I prefer the highest TPI or Net Merit sires—why pay any attention to this stuff?
The definition of insanity is to continue to do the same thing you have always done, while expecting a different result than you have always received. What has a focus on “genetic value” given us? More milk per cow lactation—but fewer lactations: lower average milk components, thus lower milk prices: shorter herdlife, thus higher replacement overhead: slower fertility, thus more reproduction expense;
extreme physiques, thus more hoof trimming and stall injury expenses. Genetic value has no “value” unless you are able to harvest a margin of profit over all input costs. Developing markets for milk from herds that will dedicate to selection on A2A2 genetics promise some serious price premiums based not on emotion, but on science.
A1 vs A2 is just the first of what may be many examples of why Genomics could be our most powerful selection tool, but by only using it to estimate PTA values, we have trivialized its true potential. Those who are locked into conventional volume-based pooled “commodity milk” marketing have nothing to be gained from a focus on A2 selection today—but the impact of this knowledge on milk’s consumers, as it gains traction in the media’s oversight on food issues, could be a worse blow to “generic jug milk” than the anti biotech reaction to rBST—because we cannot quit using it overnight to satisfy a market demand.
Short term strategies
The frequency in the Kiwi cow population does not appear to be significantly above North America’s frequencies – thus we should be able to identify A2 carriers in the USA and Canada. Study the lesson and encourage dairy leadership to become proactive in addressing what may be a future opportunity.