Replacing Barley with Protected Tallow in Ration of Lactating Holstein Cows

Twelve lactating Holstein cows were fed four rations containing 0, 5, 10, and 15% protected tallow in a switchback design. The grain allowance was decreased with each addition of tallow to make the diets isocaloric. Milk yields were not different among treatments. However, milk fat test and daily fat yield were increased with 15% protected tallow and tended to increase with 5 and 10%. High-fat diets (10 and 15%) depressed content of milk protein but did not affect daily protein production compared to control. Molar percentage of acetic acid was increased and propionic acid was depressed in ruminal fluid of cows fed 15% protected tallow compared to the control diet. Inclusion of protected tallow in the daily ration elevated cholesterol of blood serum with no effect on cholesterol in milk. Concentrations of stearic and oleic acids in milk were increased while other fatty acids (carbon 6 to 16) were decreased with the higher dietary concentrations of protected fat. Apparent digestibility of ration nutrients (dry matter, gross energy, crude protein, acid-detergent fiber, calcium, and magnesium) were not affected by the protected tallow, but digestion coefficients of ether and acid-solvent extract were increased with dietary tallow.