Dietary Choline for the Lactating Cow: Possible Effects on Milk Fat Synthesis

Abstract

Two experiments with low forage diets tested effects of added dietary choline on milk fat synthesis. In Experiment 1, 18 Holstein cows were in a 12-wk trial. Choline (0, 1.5, and 3 g/kg) was added to the concentrate portion of a 70% concentrate, 30% corn silage diet (dry matter). Treatments were applied in a switchback design with 4-wk experimental periods. Highest choline increased milk fat by .34 percentage units and fat-corrected milk by 2kg per day over controls. Rumen pH and volatile fatty acids were similar among treatments. Free fatty acids of blood serum were reduced 3.0 mg/100ml by 3 g/kg choline. In Experiment 2 with four mature Holsteins, choline was added (0, 2, 4, and 6 g/kg concentrate) in 25% corn silage and 75% concentrate diets. Treatments were applied in a 4×4 Latin square design. Addition of 4 g/kg choline resulted in 3.7 kg/day and .77 percentage unit increases of fat-corrected milk and milk fat percent, respectively, whereas fat-corrected milk and milk fat percent at 6 g/kg were only slightly higher than controls. We hypothesized that choline aided transport of mobilized free fatty acids from adipose tissue through the liver to the mammary gland.