Feed Ration Reformulation After a Forage Test
A 120-head dairy herd is fed a total mixed ration built on corn silage and alfalfa haylage. A new silage test comes back at 32 percent dry matter, 8.5 percent crude protein, and 38 percent neutral detergent fibre, with a very high lactic acid reading and a low pH of 3.8. The previous crop tested at 36 percent dry matter and 9.5 percent crude protein. The nutritionist's ration assumed the old values. Cows have dropped about 2 kg of milk per head per day over two weeks, and butterfat has slipped from 3.8 to 3.5 percent. Rumen fill looks adequate and there is no sign of clinical acidosis, but cud chewing appears reduced.
1. Interpret the forage test and connect the wet, acidic silage to the drop in milk and butterfat.
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The silage is wetter and lower in protein than the ration assumed, and the very low pH with high lactic acid indicates a strongly fermented, acidic feed. The ration was balanced on 36 percent dry matter and 9.5 percent protein, so feeding the actual silage delivers less protein and more water per kilogram of dry matter than intended, diluting nutrient intake. The high lactic acid load and low pH push the rumen toward a more acidic environment, which favours a shift in fermentation and can depress fibre digestion. Reduced cud chewing is a warning sign of subacute rumen acidosis even without clinical signs. Depressed fibre digestion lowers the acetate supply that supports milk fat, which explains the butterfat decline, and the overall energy and protein shortfall explains the milk drop.
2. Propose ration adjustments and a monitoring plan to confirm the fix.
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First, reformulate on the actual dry matter so the cows receive the intended protein and energy; the wetter silage means more fresh weight is needed per cow to deliver the same dry matter. Add a rumen buffer such as sodium bicarbonate to counter the acid load, and consider a direct-fed microbial or yeast to support fibre digestion. Raise the effective fibre in the ration, for example by increasing the alfalfa haylage or adding a coarse forage, so cud chewing and rumen pH recover. Top up protein to replace the shortfall from the lower silage protein. For monitoring, track individual cow dry matter intake, weigh the fresh weight of each ingredient daily, check rumen pH or milk fat and protein ratios weekly, and re-test the silage monthly since a wet, acidic face can shift. Confirm improvement by butterfat returning toward 3.8 percent and cud chewing normalising within two to three weeks.