Editor’s note: The following case was handled by Ueli Zaugg, dairy nutritionist from Fountain Hills, Ariz.
One summer, a dairy in Arizona experienced a drop in butterfat from about 3.5 percent to as low as 3.16 percent.
The farm was feeding barley with a fast degradability of the starch and also lots of green chop. The manure was sometimes looser than normal, which is not unusual with a lot of green chop in the diet. Metabolic disorders at freshening were minimal, and there were no increased foot problems. Breeding went well even during the summer.
Subclinical acidosis did not appear to be a problem.
Yet, conventional methods to solve the problem did not bring about any success. Adding oat hay or straw did not change the butterfat.
With the help of Bill Sanchez, of the Diamond V Corporation, herd nutritionist Ueli Zaugg found that taking a new look at fatty acids, especially the saturated fatty acids, could help turn the situation around. They started concentrating on the fatty acids in the ration, especially the unsaturated fatty acids (C18:1 and C18:2).
Sanchez recommended a drastic change in the ration with the potential loss of some milk, but an increase in butterfat. The dairyman agreed. The first step was lowering total fat in the diet. The TMR had some animal fat/vegetable blend in a molasses mix. The dairy changed to straight molasses, and dried distillers grains, bakery waste and cottonseed were drastically reduced.
Before the change, intake of the rumen unsaturated fatty acids was approximately 750 grams a day. After the change, it dropped to less than 650 grams a day. With the CPM model, it showed that the absorbed C18:1T as an intermediate of the biohydrogenation process in the rumen dropped from 77 grams to 54 grams. (The average dry matter intake for the high cows was 58 pounds.)
C18:1T served as an indicator, in this case, that the biohydrogenation pathways in the rumen had improved to the point where there was less outflow of harmful intermediates to the small intestine that could increase the risk of milkfat depression. .
There was an immediate effect on the cows. Production dropped, as predicted by the CPM model, by about 3 to 5 pounds. But the butterfat increased within a two-week period from 3.16 percent to 3.45 percent. Crude protein in the milk did not change much ― 3.16 percent to 3.19 percent.
During the following weeks, Zaugg fine-tuned the rations and the cows went back up in milk without losing any butterfat. The dairyman was pretty pleased. Not only did he receive a higher milk price, but the ration cost went down with feeding less fat.