Balancing dairy rations for rumen-protected amino acids is often an exercise in confusion. There are few hard and fast rules. Different ration formulation software programs give varying answers.
Some producers report gains in milk production; others see gains in components, particularly milk protein. Some see an increase in dry matter intake; others see an improvement in feed efficiency. It's enough to drive any rationally thinking producer to just forget about it.
That would be a mistake. With milk prices still in the doldrums and feed prices above the five-year average, improving rations is a win-win, say dairy nutritionists.
The reason? "The cost of feeding methionine and lysine is offset by feeding less rumen-undegraded protein,” says Chuck Schwab, the nation's leading amino acid expert. Schwab, professor emeritus at the University of New Hampshire, now consults with Adisseo.
"When amino acids are supplemented, you almost always make other changes to the diet and balance for rumen-undegraded protein,” he says. Supplementing the amino acids and lowering crude protein, Schwab says, can save up to 25¢/cow.
"Lowering protein in the ration without giving up milk production is especially helpful now,” says Rick Lundquist, a nutritionist who consults with large Southern dairies.
A 25¢/cow increase in income over feed costs yields a $65/cow to $75/cow gain, depending on herd average. On a 500-cow herd, that's an annual gain of $30,000 or more.
The science behind amino acid nutrition is still evolving, but the basics are firmly grounded. "Absorbed amino acids, not protein, are the cow's required nutrients,” Schwab says.
Amino acids are the building blocks for tissue and milk proteins. In dairy cattle, rumen microbes provide the bulk of protein and energy that are needed for maintenance, growth, milk production and reproduction. But in high-producing herds, particularly in early lactation, the rumen bugs simply can't meet all the cow's nutrient needs.
That's where rumen-bypass feeds come in. Typical legume protein sources such as alfalfa and animal byproducts are low in methionine.
"Methionine in milk and bacteria are 2.6% to 2.7% of crude protein; in soybean, blood, feather and meat meals, methionine is only 0.8% to 1.4% of crude protein,” Schwab says.
- May 2010