Production responses of dairy cows fed diets supplemented with ammonium salts of Iso C-4 and C-5 acids

A three-university study examined effects of ammonium salts of volatile fatty acids on dairy cows for a full lactation cycle. Objectives were a) to determine the most efficacious amount and ratio of two components, ammonium salts of C-5 acids and ammonium isobutyrate, and b) to compare responses of this optimum blend with the control in a response surface design. This design tested six blends of the two components defined by the center point and the five points of an equilateral pentagon from which response surfaces would be computed and a control. Each treatment consisted of 23 cows for a total of 161 multiparous Holstein cows. All cows were fed corn silage for ad libitum consumption, 1.8 kg of urea-mineral-vitamin-premix plus supplement based on corn grain and corn gluten meal according to milk production. Response surfaces, based on milk yield, defined an optimum blend composed of 61 g ammonium salts of C-5 acids plus 28 g ammonium isobutyrate per cow per day equivalent to 120 g aqueous blend (74% solids). The optimum blend was similar to the center point blend. Cows receiving the center point blend peaked higher and produced more milk, 4% fat-corrected milk, milk protein, and total solids than control cows. For the first trimester of lactation, milk yields for control and center point blend were 28.6 and 31.8 kg. The 305-day milk, 4% fat-corrected milk yields, and dry matter intakes (kg) were: control 20.5, 19.7, 17.3; center point blend 23.2, 21.6, 17.5. Increased milk production was associated with improved feed utilization. No effect on health or reproduction was observed.