Farming Magazine - May, 2010

COLUMNS

Dairy Nutrition: Nutrient Density

By John S. Hibma

Correctly balancing dairy rations is always a bigger challenge when times are tough for the dairy industry. While I continually stress the need to focus on high-quality forages to help reduce the need for supplements, the truth of the matter is that it’s nearly impossible to keep cows milking at the high levels necessary to maintain cash flow without some grain in their diets.

Still, many dairy farms in the Northeast have moved to pasture-based operations in which they’re able to graze their herds for much of the year and supplement them with good hay or haylage during the winter months. They keep cows milking with minimal amount of purchased grains. While they don’t make record-breaking amounts of milk, the lower cost of feed allows their income-over-feed-costs (IOFC) to be adequate to sustain their type of business model.

The dairy farms that have chosen to milk a lot of cows for various reasons usually have incurred significant amounts of debt that require their herds to produce 20,000 pounds of milk, at the minimum, to pay the bills. Those are the cows that need higher levels of grain supplementation to meet nutritional requirements to produce that kind of milk. And, many of those dairies have found themselves in a financial battle to survive.

For a cow to make over 20,000 pounds of milk in a lactation, she must consume a daily diet that is packed with nutrition. Every bite, every mouthful of feed must be as nutritionally dense as possible. However, cows also have differing levels of feed intakes dependent upon their size and level of milk production. Energy, protein, vitamin and mineral levels in a ration must be formulated so they “fit” into whatever a cow’s dry matter intake happens to be.

As an example, a 1,400-pound Holstein producing 80 pounds of milk on a day that’s 35 degrees Fahrenheit should consume about 51 pounds of feed dry matter (DM). A typical New England ration might balance out to 22.4 pounds DM (80 pounds as fed) of corn silage and 3 pounds DM (15 pounds as fed) of haylage. This leaves 25.5 pounds DM (28.4 pounds as fed) of grains or feed by-products to make the 51 pounds of intake.

Even though many nutritionists no longer rely completely on the “Net Energy for Lactation” (NeL) calculations to meet energy requirements for milk cows, it’s still a useful number with which to illustrate whether a diet is supplying enough energy. NeL is expressed in mega-calories per pound (mcal/lb). For the cow in this example, the ration must have an energy density of .75 mcal/lb DM. Each pound of DM must contain 750,000 calories. The Cornell-Penn-Miner Dairy Ration Analyzer, (CPM v3.0.10), was used to arrive at these calculations.

The NeL of the corn silage in this ration calculates to .75 mcal/lb, as well. The haylage, however, comes to only .52 mcal/lb and even though it only contributes 3 pounds of dry matter to the ration, the poor quality pulls the average down so that the grain mix must contain .80 mcal/lb so the entire ration averages .75 mcal/lb., The higher you manage to keep the Nel of your forages, the less energy you need to purchase. Unfortunately, much of the haylage produced in the Northeast seldom makes it to .55 mcal/lb, which pretty much forces us to formulate grain mixes that have to be at .80 mcal/lb.

A second important factor in balancing this ration is making sure the protein level is adequate. In this example, the dairy farmer may be tempted to replace a few pounds of grain with corn silage. We reduce the grain to 22.5 pounds DM and raise the corn silage up to 25.5 pounds DM to meet dry matter requirements for the cow. Interestingly enough, the CPM model predicts we have enough energy in the ration to continue to support 80 pounds of milk. But, the grain mix has significantly more protein in it and taking away the 3 pounds of DM reduces the predicted milk production by about 6 pounds of milk.

In this case, the savings in grain cost to the dairy would have been about 56 cents per cow per day, but the 6 pounds of lost milk would be near $1 per cow per day with a current milk price of about $16 a hundredweight. The protein density in the grain mix would have to be increased so adequate protein is in the diet to continue to support 80 pounds of milk production. This would cause the cost per ton of grain to increase and, most likely, the cost of the ration would be back to where it was originally, or possibly even higher.

Vitamins and minerals have to be considered in the same manner. For many additives put into your grain mix, such as salt or buffer, the amounts are added to a batch of grain based upon the presumed amount it will be fed to the cow. In the case of our grain mix in the previous example, buffer and salt may have been added to the mix to supply 8 ounces of buffer and 4 ounces of salt. By reducing the amount of the grain fed, the cow will get neither of those two levels of buffer or salt.

A major consideration that every dairy farmer must keep in mind when adjusting grain mixes or switching from one supplier to another, based upon price, is the nutrient density of the product he is purchasing. A mix could be $30 to $50 cheaper, but it may not have the desired calories or protein to meet a desired level of milk production.

Figuring all of this out can be a lengthy and frustrating process, not to mention costly. More often than not, a dairy farmer must enlist the help of a feed professional who can sort through the myriad of complexities that make up a dairy cow diet. In the end, we have to focus on the financial bottom line. Every dairy farm’s situation is different when it comes to deciding how much milk to produce and what it will cost to make it and, in the end, you usually get what you pay for.

The author is a dairy nutritional consultant and works for Central Connecticut Farmer’s Cooperative in Manchester, Conn. Comment or question? Visit www.farmingforumsite.com and join in the discussions.