switching a dairy cow to grass
A Kentucky farmer writes: I am wanting to do grass-fed dairy. How important is it to buy a cow that is already on that diet and/or comes from grass-fed genes? The peanut gallery on FB seems to think that without grass-fed genes dairy cows without grain will still produce lots of milk but at the expense of their body condition. I want to make sure the cow I buy can at least be transitioned to grass-fed, even if there needs to be a transition period to get there.
Hi, thanks for reaching out!
Our own experience, such as it is, is that every cow has grass genetics, thanks to thousands of years of an all-grass diet, and a hundred or so years of grain feeding hasn't altered genes so much as it has altered their expression. An older animal that has experienced grain feeding will be expressing tolerance to a grain diet, not a genetic imperative for grain. She'll probably have a smaller rumen than an all-grass animal, and her ruman flora will emphasize carbohydrate-metabolizing bacteria over cellulose-metabolics. So she'll have a hard time getting enough grass in her gut and breaking it down effectively for both body maintenance and milk production. Given also that a dairy animal is selected for a predisposition to put calories in her udder rather than on her back, a grain-fed dairy cow that is switched to grass is probably going to be thinner than you'd like, at least for a transition period of several seasons/years. In all likelihood she'll never be all the cow she might have been if she'd been raised on grass from the beginning.
That said, we've transitioned more than one grain-and-hay fed dairy animal to all grass. Our experience has been that age will be a big factor in our degree of success; the younger they are, the easier and more effective the transition. We would recommend a gradual switch, decreasing grain over the course of a spring/summer/fall/winter, and eliminating it altogether in late spring when pasture grasses are at their most nutritious. Then we'd tough it out for a couple of years, monitoring her condition less by how she looks than by how she behaves. If after a couple of years on nothing but grass we still weren't impressed with her performance we'd stop breeding her, fatten her up, and put her in the freezer. None of her offspring would be used for breeding.
We should note here that there is a pasture wisdom that builds up in a herd, even a small one, and it means that over time you'll see an increasing level of health that doesn't seem to be accounted for by either genetic shift or pasture improvement. We would attribute this bloom of health to an acquired, communicated botanical wisdom; that is, over time grass cows share knowledge about plant properties, knowledge that lets them reach a level of health we had no previous experience of. It's one of the biggest satisfactions of being a grass dairy farmer.
A side note; with occasional exceptions, a grass cow is going to give less milk per year than a grain-enhanced one, but she'll give more milk over her lifetime because she'll live longer.
We go into more detail on this question in our field guide Family Cow Basics.
