COMPARISON OF 3 METHODS FOR INCORPORATION OF LIQUID FAT INTO DIETS FOR LACTATING DAIRY-COWS

Two experiments were conducted to determine whether method of incorpor ation of tallow (iodine value = 57.7) into a TMR for lactating dairy c ows affected DMI, milk production or composition, ruminal characterist ics, or nutrient digestibilities. In Experiment 1, 8 Holstein and 8 Je rsey cows were fed diets containing 1) control, no fat; 2) fat (5% of DM) added first to the concentrate; 3) fat added first to the haylage; and 4) fat added as the last ingredient in the TMR. The DMI was lower when fat was added last to the TMR; DMI was decreased for Jerseys, bu t not Holsteins, when fat was added first to the concentrate. Milk pro duction was increased, and milk fat percentage decreased, by fat suppl ementation, but neither differed among application methods. Milk prote in percentage was decreased by fat supplementation but was decreased l ess when fat was added last to the TMR. Production of milk CP, true pr otein, and casein protein was greater when fat was first mixed with ha ylage or added last to the TMR. In Experiment 2, four Holstein cows wi th ruminal cannulas were fed the same diets. Ruminal fermentation char acteristics and apparent total tract digestibilities of DM, OM, CP, ND F, ADF, and ash were not different among diets. Digestibility of total fatty acids was decreased when fat was added first to haylage or last to the TMR. Incorporation method had relatively minor effects on vari ables.