Butterfat percent is low and jumping around quite a bit on many farms.

In indoor systems, the probable cause would be insufficient fibre in the diet, leading to rumen acidosis, but this is not the case when cows are out grazing. The symptom is associated with grazing low covers of lush and leafy grass that is low in fibre. But adding in extra fibre to the diet does not lead to a rise in milk fats.

This is because the issue is not caused by low rumen pH, but by the fatty acids generated when the rumen digests young leafy grass, and it is in the udder itself where milk fats drop.

There is no quick-fix.

Time seems to solve it, either grass quality changes or the rumen microbes adapt to the grass. In the meantime, keep the focus on hitting residuals.

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