Researchers at the University of Guelph recently tried to determine what happens to feed temperature, feed intake, feed sorting behavior and milk production of dairy cows when you add water to a total-mixed ration.

They fed diets with the same ingredient composition, but differed in dry matter concentration due to the addition of water. Researchers found that greater amounts of water added to the TMR resulted in higher increases in feed temperature in the hours after feed delivery, greater sorting against long particles, and decreased dry matter intake, thereby reducing the overall intake of starch and neutral detergent fiber. Milk production and composition were not affected by the addition of water to the TMR. But milk production efficiency did increase as the amount of water added to the TMR rose. The increases in feed temperature in the hours after feed delivery were enhanced by higher ambient temperatures. The scientists say this may be indicative of feed spoilage and thus may have contributed to the reduced DMI observed.

Overall, results suggest that the addition of water to high-moisture TMR (less than 60 percent DM) containing primarily haylage and silage forage sources will not always discourage cows from sorting, but rather may increase this behavior and limit the nutrient consumption of cows, particularly when ambient temperature is high.