How to produce milk with a normal milk fat percentage is a major problem for California dairymen during the period from May to October each year. There are indications that high temperatures (85°F and up) plus the feeding of large amounts of green chop forages, which reduce fiber intake, both depress the fat composition of milk. There are a few feedstuffs and additives which, when added to the ration, will partially counteract this seasonal depression in the percentage of fat in milk; however, cost and/or low palatability makes it impractical to use most of these in a commercial dairy operation. An additive that has been suggested as promising is dried whey—a by-product of the processing of butter and cheese. Dried whey product is highly palatable and, when fed at the rate of 10 per cent of the ration, has been successfully used to maintain a normal fat test under conditions of high temperature and low fiber rations. When dried whey product is incorporated into pelleted concentrates at this level, however, mechanical difficulties develop in the pelleting process. Reduction of the level to 5 per cent of the pelleted concentrate has overcome this problem but the effect on fat percentage at this level has not been tested.

Dr. M. R. Lambert of Foremost Foods Co. supplied the dried whey product and funds for extra milk testing. Herald Habenicht and the staff of the Loma Linda University Dairy assisted in conducting the trial.