Farming Magazine - June, 2009

COLUMNS

Dairy Nutrition: Single-Group Diets

One of the most troubling management faux pas I see being made on many dairies in the Northeast is the use of the single-group feed ration. Even though the dairy industry has acknowledged for years the nutritional advantages and cost savings associated with multiple feed rations based upon stage of lactation and milk production, many dairy farms continue to mix just one ration that’s fed to all milk cows, regardless of how much milk they produce or how many days they’ve been milking.

As dairy cows progress through their lactations their nutritional needs change. A cow in early lactation requires a diet that has a higher nutrient density. Her nutritional requirements are highest as she approaches and maintains her peak milk production in the weeks and months after calving. In those first two weeks or so after she freshens, the protein, energy, vitamins and minerals must be packed into a “smaller package” while she’s transitioning to her full feed intake level, and those rations generally cost more. A cow in later lactation does not require as dense of a ration and can derive more of her nutrition from farm-grown forages such as corn silage or haylage and less from the grain, which makes the ration cheaper.

Still, there are many dairy farms that feed only one ration that’s balanced for a level of milk production that more closely approximates the average milk production of the herd. Single mix rations by-and-large deprive fresh cows of their potential milk peaks while, at the same time, overfeed the late-lactation cows, opening the door to overconditioning and metabolic disorders if and when they freshen again. A key point to understanding the importance of multiple rations is that the lower-production diet can be reformulated to cost less money rather than having those cows eating less pounds of a higher-producing diet.

To help illustrate this, let’s look at a dairy cow diet that’s formulated to support 80 pounds of milk production with 4 percent milk fat and 3.1 percent milk protein. The cow is expected to eat about 52 pounds dry matter (DM), consuming 66 pounds of corn silage and 28 pounds of a 24 percent complete pellet. The corn silage is priced at $40 a ton and the pellet is priced at $320 a ton. The cost of the ration is $5.80 per cow per day. Another cow in the same group who’s producing 65 pounds of milk would be expected to eat about 10 percent less DM (47 pounds) and if the ration is in the same proportions the cost of her diet would be $5.22.

However, the cow producing 65 pounds of milk does not need 25 pounds of the pellet (28x.9). A more cost-effective diet would have her eating only 22 pounds of the pellet along with the 66 pounds of corn silage. This diet will cost only $4.85—a savings of about 37 cents per day.

If we look at a herd of 100 cows that can be divided into two even groups of 50 cows each, the savings of 37 cents per cow per day becomes over $18 per day, or well over $500 per month, or over $6,000 per year. This example illustrates the money it costs a dairy farmer by overfeeding the lower tier of his herd with an expensive ration.

The flip side of these single mix diets is the money that’s lost when a diet is formulated for only 65 pounds of milk and the fresh cow that’s headed for peak milk production must eat that diet. Regardless, if a fresh cow can consume more total pounds of that diet, the total calories, protein, vitamins and minerals will fall far short of her needs to reach that “desired” peak. Even if she can consume 10 to 20 percent more of that mix, the nutrient density is nowhere near enough to support the 100 pounds of milk production you’d like to see from her.

To illustrate this point we’ll go back to the 65 pounds of milk production and the ration that contains 22 pounds of pellet and 66 pounds of corn silage with the intention that the entire herd will be consuming it at different DM levels dependent upon their individual milk production. If our fresh cow that’s a month into her lactation would be able to consume about 56 pounds of DM, the proportions of the mix will only allow her to eat about 26 pounds of the pellet—several pounds less than what she should for 100 pounds of milk production—and many more pounds of the corn silage, which is limiting her protein requirements. This cow may be able to produce 80 to 90 pounds of milk for a short while by milking some fat off of her back. But, in a matter of a few weeks she’ll settle back to 70 or 80 pounds of milk, which is all the ration is able to support.

Peak milk production in your herd is where the greatest profit and income-over-feed-cost is realized. I continue to encourage dairy farmers, even in these trying economic times, to push their cows to make more milk and maximize total milk production in a 13 to 14-month lactation. The mid-range, single mix feed rations that many dairy farmers feed to their herds effectively limit the top milk production that their herd’s are capable of. By not separating your milk herds into at least two groups you lose money on both ends: by spending too much money for the lower producers and not getting the milk revenues out of the top producers.

The author, a longtime Farming contributor, is a dairy nutritional consultant and works for Central Connecticut Farmer’s Cooperative in Manchester, Conn.