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.