Dried Whey-Fat Blend Product as a Feed for Lactating Dairy Cows

Twenty lactating Holstein cows were in a switchback design with three periods of 4 wk each to evaluate a dried whey-fat blend product. The whey-fat blend, consisting of a blend of acid whey and soybean oil, contained 8.5% crude protein and 22.2% ether extract. Diets consisted of ad libitum corn silage and alfalfa hay, plus concentrate mix with or without whey-fat blend product fed at 1 kg/3 kg milk produced. The whey-fat blend concentrate mix contained 30% dried whey-fat blend product in place of equal portions of corn and oats. Control and whey-fat blend diets averaged 17.2 and 15.6% crude protein, 2.6 and 6.1% ether extract, and 20.2 and 19.0% acid detergent fiber (percent of dry matter). Milk yield (24.6 and 24.7 kg/day) and milk protein (3.03 and 3.01%) were similar for control and whey-fat blend diets, but fat (3.18 and 2.86%) was less for cows fed the whey-fat blend product. Milk flavor was not affected by diet, although milk fat from cows fed whey-fat blend contained more unsaturated fatty acids. Ruminal concentrations of acetate decreased and butyrate increased, whereas concentration of propionate was unaffected in cows fed whey-fat blend. Dry matter intakes were similar for both diets. Whey-fat blend can be an acceptable feed for lactating cows but should be amounts smaller than fed in this experiment to avoid possible milk fat depression and problems with feed handling.