Effects of feeding increasing dietary concentrations of fat on the performance of lactating dairy cows

In experiment 1 treatments were: control, no fat; control, 3% calcium salts of long-chain fatty acids (Ca-LCFA); control, 6% Ca-LCFA; and control, 9% Ca-LCFA. Dry matter intake and production of milk, milk protein, and solids-not-fat (SNF) were not altered greatly by feeding up to 6% Ca-LCFA in the diet. Nutrient utilization was optimized when between 3 and 6% Ca-LCFA were added to the diet; however, calcium digestibility was linearly decreased by feeding Ca-LCFA. Ca-LCFA may be fed to supply up to 6% of the dietary dry matter (DM) without having deleterious effects on ruminal fermentation and nutrient utilization.In the second experiment treatments were: control, no fat; control, 6% extruded whole soybeans (EWSB); control, 12% EWSB; and control, 18% EWSB. Feeding EWSB increased DM and gross energy intakes and the production of milk and 4% fat-corrected milk (FCM) and did not alter significantly the percentages of milk protein, fat, and SNF. Ruminal pH and molar percentages of VFA were not altered significantly and there were only small decreases in apparent nutrient digestibilities when cows were fed EWSB. Utilization of energy and nitrogen were not altered greatly by feeding any amount of EWSB. Extruded whole soybeans can provide up to 18% of the total dietary DM fed to high-producing dairy cows during early lactation without having major negative impacts on performance.In the third experiment treatments were: control, no fat; control, 16% EWSB; control, 16% EWSB, 3% Ca-LCFA; and control, 16% EWSB, 6% Ca-LCFA. Dry matter intake, production of milk, 4% FCM, milk fat, milk CP, and milk SNF were not greatly altered by feeding 16% EWSB or 16% EWSB plus 3% Ca-LCFA in the diet, but production of milk and milk components were decreased when 16% EWSB and 6% Ca-LCFA were included in the diet. Intakes of gross energy and total tract apparent digestibilities were decreased by feeding 16% EWSB and 16% EWSB plus 6% Ca-LCFA in the diet but differences were small among the other treatments. Ca-LCFA can supply up to 3% of the dietary DM when fed in diets containing 16% EWSB without having deleterious effects on most variables measured in this study. (Abstract shortened with permission of author.)U of I OnlyETDs are only available to UIUC Users without author permissio