CONCEPTIONS Dairy Route Newsletter February March 2020
numbers of dairymen are now including screening sires for Beta Casein
variants, A2 considered a “good” casein and A1 a “bad” casein (there are also the
letter mutations B etc.).
Are conventional milk handling chains ready for this? NO. So far it is a specialty product you find at Meijer’s Thrifty Acres or Mooville Creamery. So should you breed for it anyway?
All the studies to date have been done for human benefits, outside the dairy industry. Given the association of A1 Beta Casein with human digestive problems and auto-immune disorders nothing relating to its effect on calves has been studied as yet. But it would be easy to expect calves from A2 cows might have less scours, for example, or a better immunity profile. Studies are needed. As this is not a potential drug, you won’t see any pharmaceutical company (like Zoetis) doing DNA studies on this in the way they did for “wellness traits”.
In Europe, where cheese production drives the dairy industry, milk Protein % is the biggest part of farm milk checks (Butterfat % is currently a bigger payout in the USA and Canada). Decades of selection in favor of Kappa Casein variant B has gone on, which is why you now see this data on bulls as well. For any given level of Protein %, cheese makers see 7% more cheese yield on an AB cow, and 15% more cheese yield on a BB cow, than you see from the average AA cow.
So both Beta Casein and Kappa Casein are forms of milk proteins, produced in the rumen, some of which make cheese curds and some that remain in the whey, all of which are digestible when in the right gene variant form. The lower the rumen acidity, the higher their quality and more desirable their flavor (rations high in digestible fiber produce the best Caseins). At this point the only way to make money from B Kappa Casein is to be producing cheese on-farm, but as in Europe, a true “Cheese Yield” payment market could develop here.