Comparison of three methods for incorporation of liquid fat into diets for lactating dairy cows

Two experiments were conducted to determine whether method of incorporation of tallow (iodine value = 57.7) into a TMR for lactating dairy cows affected DMI, milk production or composition, ruminal characteristics, or nutrient digestibilities. In Experiment 1, 8 Holstein and 8 Jersey 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, but not Holsteins, when fat was added first to the concentrate. Milk production was increased, and milk fat percentage decreased, by fat supplementation, but neither differed among application methods. Milk protein percentage was decreased by fat supplementation but was decreased less when fat was added last to the TMR. Production of milk CP, true protein, and casein protein was greater when fat was first mixed with haylage or added last to the TMR. In Experiment 2, four Holstein cows with ruminal cannulas were fed the same diets. Ruminal fermentation characteristics and apparent total tract digestibilities of DM, OM, CP, NDF, 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 variables.