By Rick Lundquist, Ph.D.
“Fat tests lowest in 20 years.” That was the headline on the Chicago Mercantile Exchange (CME) Daily Dairy Report for June 23, 2010. Fat tests averaged 3.68% in the first five months of 2010, which was the lowest in 20 years, and continue to decline seasonally, according to the report.
The low fat tests seem to be ubiquitous this year. In conversations and e-mail exchanges with nutritionists and dairy producers across the country, there appears to be an inordinate number of dairies that have been affected. These are dairies that typically run normal fat tests but for some reason have experienced unexplained difficulty this year with their butterfat. They’re in diverse areas like New England, the Southwest, California, Idaho, the Southeast and the Midwest.
These dairies feed totally different rations from each other and experience extremely different weather. There’s been no obvious common denominator. Some of the possible culprits that have been mentioned include immature, highly degradable corn and corn silage in the Midwest, increased use of distillers grains (DDG), and tallow that contains higher concentrations of unsaturated fatty acids because the fed cattle diets contain more DDG.
But these are not common to all of the dairies with fat test problems. The one “theory” that comes closest to a common cause is vomitoxin contamination of the 2009 corn crop and the byproducts from the corn (DDG, corn gluten feed). I’m not aware of any direct relationship between vomitoxin and butterfat, but I’m sure you could theorize an effect on the rumen microbes or absorption of nutrients in the gut. It will be interesting to see what happens to fat test on these dairies as we get into a new corn crop.
If you’re experiencing fat test problems, you might want to increase your potassium levels in your rations this summer. A study reported last week at the American Dairy Science Association annual meetings in Denver showed that potassium from potassium carbonate may shift rumen fermentation to favor higher fat tests. The results showed that increasing potassium in the diet increases rumen pH, but also may influence the biohydrogenation pathways that prevent milk fat depression.
Reference: T.C. Jenkins, E.Block, and J.H. Harrison. 2010. Shifts in fermentation and intermediates of biohydrogenation induced by potassium supplementation into continuous cultures of mixed ruminal microorganisms. J. Dairy Sci. 93, E-Suppl. P. 577.