Acetate Dose-Dependently Stimulates Milk Fat Synthesis in Lactating Dairy Cows

Background: Acetate is a short-chain fatty acid (FA) that is especially important for cows because it is the major substrate for de novo FA synthesis. However, the effect of its supply on mammary lipid synthesis is not clear.

Objective: The objective of this experiment was to determine the effect of increasing acetate supply on milk fat synthesis in lactating dairy cows.

Methods: Six multiparous lactating Holstein cows were randomly assigned to treatments in a replicated design to investigate the effect of acetate supply on milk fat synthesis. Treatments were 0 (control), 5, 10, and 15 mol/d continuously infused into the rumen for 4 d. Rumen short-chain FAs, plasma hormones and metabolites, milk fat concentration, and milk FA profile were analyzed on day 4 of each treatment. Polynomial contrasts were used to test the linear and quadratic effects of increasing the substrate supply.

Results: This substrate increased milk fat yield quadratically (P < 0.01) by 7%, 16%, and 14% and increased milk fat concentration linearly (P < 0.001) by 6%, 9%, and 11% for 5, 10, and 15 mol/d, respectively, comparing with the control treatment. Increased milk fat yield predominantly was due to a linear increase in 16-carbon FAs (P < 0.001) and a quadratic increase in de novo synthesized FAs (

Conclusions: Increasing acetate supply to lactating cows increases milk fat synthesis, suggesting that nutritional strategies that increase ruminal acetate absorption would be expected to increase milk fat by increasing de novo FA synthesis.

Source: Natalie L Urrutia Kevin J Harvatine ,The  Journal of Nutrition, Volume 147, Issue 5, 1 May 2017, Pages 763–769