Feeding a modern herd of dairy cows is a complex process that becomes even more difficult this time of year. This complexity does not include the additional stress that winter weather creates on stoic farm employees as they mix precise dairy rations in the face of howling wind and blinding snow.

Most dairy herds run out of last year’s corn silage (chopped, fermented corn) and must start feeding this year’s crop now. Although the silage may look like the same and may even be the same variety, growing conditions have a tremendous impact on its nutrient content. Farmers are masters at controlling variables, but controlling the weather is still beyond their capability.

Corn silage grown during a hot wet summer will have different levels of energy and nutrients than corn silage grown in a hot dry summer. Cool summers or summers with fewer sunny days, or wet weather at harvest time, or dry weather during silking, all have an impact on silage quality. This uncontrollable variability is both the bane and the blessing for the family owned dairy farm. On the one hand, adjusting dairy rations for optimal milk production is a constant challenge. On the other hand, the level of variability is so great that corporations find it too risky to undertake the vertical integration like in the pork and poultry industries.

The challenge facing a dairy farm’s nutritionist this time of year is that he or she is working with a feed source that is still undergoing a metamorphosis of sorts. In layman’s terms, the corn silage has not had enough time to fully “cook.” More technically, the process of fully fermenting a pile of say 10,000 tons of silage takes a full 3 to 4 months. Harvested in September, the bacteria in the silage have not fully completed their growth cycle which produces lactic and acetic acids, both natural preservatives. Until that time, the nutrient content of the pile is constantly changing. If there is one thing cows don’t like, it is change. They don’t like change in their daily routine and they especially don’t like change in their diet.

On a modern dairy farm, the nutritionist’s job is to take whatever the dairy farmer has for forage, analyze it for nutrient content and devise a ration of purchased feedstuffs and minerals that when mixed with the farm’s grown forages, will keep cows healthy and allow them to produce milk at their genetic potential. A typical corn silage analysis will provide information on the levels of ash, lactic acid, acetic acid, butyric acid, water, sugar, acid detergent fiber, neutral detergent fiber, total digestible nutrients, lignin, crude protein, digestible protein, crude fat, net energy and minerals. These and other nutrient levels are determined through wet chemistry, near infrared reflectance, and fermentation tests at laboratories throughout the U.S. The results of these tests are entered into computer models to help develop the precise rations that are fed to cows.

Current Conditions
In New York, the 2008 corn silage, although good, is turning out to be a lower quality than 2007’s crop. Although yields were excellent, producers will probably find it more difficult to make milk this coming year. Everyone is hoping that this year’s December slump will be temporary and that January’s forage tests will be bring better news to producers, nutritionists and most especially, cows.