Caloric Value of Acetate and Propionate for Lactating Dairy Cows

Two mature Holstein cows with rumen fistulas were fed hay, corn silage, and concentrate in a fixed ratio (air-dry basis) of 5:15:20 and in quantity intended to minimize tissue energy change. Acetate (A) or propionate (P) or an equicaloric mixture (M) of A and P, prepared by partially neutralizing (pH 4.4) respective acids with NaOH, was diluted, and infused (19 liters daily) into the rumen continuously for 9 days to supply about 10g of ration metabolizable energy; dry feed allowance was reduced accordingly. A water (control) infusion preceded each of three series of treatments (A, M, and P randomly arranged), and all data were expressed as deviations from the series control. The experiment was a randomized complete block design with six cowseries combinations as blocks.