A new script unfolds when corn silage replaces some alfalfa hay

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click image to zoom In February, The Academy Awards recognized the best actors.

In concert with that, another group came out with the Razzies to recognize the worst actors.

It’s time to recognize some more actors. They aren’t household names, but important nonetheless. Their roles have taken on added significance in your lives — and the lives of your cows.

Because alfalfa hay has gotten so expensive — even scarce in some locations — many dairy farmers have adjusted their rations. Some are feeding more corn silage. Yet, there may be some unintended consequences with this kind of a switch if you do not pay enough attention to the fermentability of starch and fermentability of fiber in the ration. The “bad actors” inside a cow’s rumen could take on a more significant role if that were to occur.

High-priced hay

In recent months, many farmers have had to pay upwards of $300 per ton for quality hay.

“As a result of high prices and the smaller supplies of alfalfa hay, dairymen have started feeding less alfalfa hay in their dairy rations,” says hay market analyst Seth Hoyt. In 2010, producers in California fed their milk cows 11.15 pounds of hay per cow per day, on average, and that dropped to 8.6 pounds in the third quarter of 2011.

One dairy in Idaho, he said, was feeding 14 pounds of hay in its ration last summer, but now is at 7 pounds. Meanwhile, the dairy increased corn silage from 45 pounds to 65 pounds per cow per day.

Risk factors

Corn silage, which is moderate to high in starch and low to moderate in effective fiber, can create a different situation in the rumen than alfalfa hay, which is low in starch and high in effective fiber. Without proper adjustments, fermentation pathways can be altered and milkfat depressed.

According to Tom Jenkins, professor of animal and veterinary sciences at Clemson University, there are three risk factors when feeding higher amounts of corn silage:

• Lipid (or fat) content which sometimes can vary, but may be on the high side.

• Rate of starch digestibility.

• Yeast and mold.

Depending on which risk factors are present, producers may need to consider binders to deal with high yeast and mold, and they may need to consider backing off on other fat sources in the diets to deal with higher fat coming from silage or reducing other starch sources that have high rates of digestibility, Jenkins says.

Practical strategies

“It really depends on how you formulate your rations,” says Elliot Block, senior manager of technology at Arm & Hammer Animal Nutrition. When feeding more corn silage, it’s important to know the feeding values, including fermentability of starch and fermentability of fiber.

The problem occurs when people use generic values for corn silage rather than going out and testing their own feedstuffs.

It may be necessary, depending on test results, to balance the corn silage with other feed ingredients that are lower in starch, Block says.

Squelch the bad actors

Regardless, it is good know about the possible detrimental effects that can occur in the rumen if things aren’t handled properly. There are some “bad actors” out there that are ready to step in and take a leading role.

Bad actors can become more prominent when there is a reduction in rumen pH, a low level of neutral detergent fiber, and an increase in dietary starch.

Researchers are learning more about the biohydrogenation pathways within the rumen that lead to the formation of fatty acids.

It is becoming increasing clear that ration adjustments play a crucial role. Even harvest maturity of corn silage can affect the transformation of fatty acids in the rumen, according to article in the March 2012 edition of Journal of Dairy Science, written by Dutch scientists. Not surprisingly, they found that an increase in the starch-to-fiber ratio resulted in a decrease in milkfat content.

Research presented by Washington State University dairy scientist Joe Harrison at the American Dairy Science Association annual meeting in 2010 shows that potassium carbonate supplementation in the diet can help alleviate this problem. In experiments, an end-product of the biohydrogenation process — stearic acid — increased with increasing levels of potassium carbonate supplementation. Meanwhile, two fatty acids associated with milkfat depression — trans 10 C18:1 and trans 10 cis 12 CLA — decreased with potassium supplementation.

Bottom-line: Be aware of the big picture. Talk to your nutritionist about the possible detrimental effects on milkfat when the diet is tilted toward more corn silage and less alfalfa hay.

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