Holstein cows (n = 33) were assigned to one of three diets containing soybean meal, supplemental fat from extruded soybeans, or supplemental fat from Ca soaps of fatty acids. Total mixed diets containing (DM basis) 25% corn silage, 25% alfalfa hay, and 50% of the respective concentrate mixtures were fed wk 4 through 15 postpartum. Milk production (29.2, 32.4, and 31.8 kg/d) was higher for cows fed supplemental fat diets. Milk protein percentages (2.99, 2.93, and 2.81) were higher for cows fed the soybean meal diet and were higher with extruded soybeans than with Ca soaps of fatty acids. Milk fat percentages (3.20, 2.69, and 3.47) were higher for cows fed Ca soaps of fatty acids than for cows fed extruded soybeans. Milk fat from cows fed supplemental fat was more unsaturated than from those fed soybean meal and was most unsaturated from cows fed extruded soybeans. Dry matter intakes (17.8, 18.4, and 16.6 kg/d) were not significantly different among diets. Extruded soybeans and Ca soaps of fatty acids were equally effective in increasing milk production, but milk fat content was reduced, and the proportion of unsaturated fatty acids in milk fat was increased, with extruded soybeans.

Holstein calves were used wk 1 to 12 after birth to evaluate three sources of nonstructural carbohydrates that differed in ruminal degradability (corn, barley, and dried whey) with two sources of CP (normal and extruded soybean meal) that also differed in ruminal degradability. Nonstructural carbohydrates were most degradable in the dried whey diets and least degradable in the corn diets, and protein was more degradable in soybean meal than in extruded soybean meal. Pelleted diets were formulated to be isonitrogenous at 18% CP and contained (DM basis) 20% ground alfalfa hay, the respective carbohydrate and protein sources, vitamins, minerals, and antibiotic premix. All calves received 4.5 kg/d of milk during wk 1 to 4 and 2.3 kg/d during wk 5. The BW gains during wk 1 to 12 were higher (.80, .70, and .70 kg/d) for calves fed corn than for those fed barley and dried whey, respectively, and were slightly higher for calves fed extruded versus normal soybean meal (.76 and .71 kg/d). Corresponding DMI (1.47, 1.34, and 1.31 kg/d) were higher for calves fed corn than for those fed barley and dried whey and were higher for calves fed extruded versus normal soybean meal (1.43 and 1.32 kg/d). Trends in BW gains and feed intakes for wk 1 to 5 and 6 to 12 were similar. Feed to gain ratio was similar for all diets in all periods. The BW gains of calves tended to be greater when they were fed diets containing nonstructural carbohydrates and protein that was less ruminally degradable.

A study was conducted to evaluate the lactational response of high producing cows to diets supplemented with fat that contained additional ruminally degradable carbohydrate from a molasses plus fat product and dried whey. Forty Holstein cows were randomly assigned within lactation group to receive diets containing 2% tallow with or without molasses or dried whey wk 4 through 16 postpartum. Cows were fed 1) the control TMR of 25% corn silage, 25% alfalfa hay, and 50% concentrate mix, 2) the TMR containing fat, 3) the TMR containing molasses and fat, or 4) the TMR containing dried whey and fat. Production of milk and 3.5% FCM was increased by supplemental fat. Milk protein and fat percentages were not affected by supplemental fat with or without molasses or dried whey. The DMI and BW were similar for all diets. Production efficiency (3.5% FCM/DMI) was higher for cows fed supplemental fat diets, and cows fed tallow alone were more efficient than those fed tallow with molasses or dried whey. Tallow did not influence ruminal concentrations of various VFA. Molar percentage of butyrate was higher for cows fed the TMR containing molasses plus fat or dried whey plus fat than for cows fed the TMR containing fat. The TMR containing 2% tallow increased milk production, but no economic advantage was derived from inclusion of an additional ruminally fermentable carbohydrate as molasses or from dried whey with fat.

Thirty-six Holstein cows were assigned to one of three diets containing soybean meal (16% CP), added fat from extruded soybeans (16% CP), and added fat and protein from extruded soybeans plus soybean meal (18% CP) to determine whether feeding additional protein would prevent the depression in milk protein percentages usually experienced when cows are fed additional fat. Total mixed diets containing 25% corn silage, 25% alfalfa hay, and 50% of respective concentrate mixtures were fed individually wk 4 through 16 postpartum; pretreatment (wk 3 postpartum), milk production, and composition data were used as covariates. Milk production (33.0, 35.8, and 34.2 kg/d) was higher for cows fed added fat. Milk protein (2.92, 2.88, and 2.83%) and casein (2.16, 2.13, and 2.09%) tended to decrease for cows fed added fat and did not increase with higher dietary protein. Dry matter intakes (20.9, 20.7, and 19.8 kg/d) and BW were similar for all diets. Supplementing additional CP to a diet containing added fat did not prevent depression in milk protein percentage.

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