Effect of acetate absorption on the daily rhythm of milk synthesis and plasma hormones and metabolites in dairy cows

Document Type


Publication Date



American Dairy Science Association


Journal of Dairy Science




Suppl. 1






short-chain fatty acids, nutrient entrainment, peripheral clocks


Time of feeding and nutrient absorption alters the daily rhythm of milk synthesis, likely by entrainment of the circadian clock of the mammary gland. Acetate supplementation increases milk fat in lactating cows and acetate also entrains circadian clocks in murine and cell models. The objective was to investigate the effect of time of acetate absorption on the daily rhythm of milk synthesis and plasma hormones and metabolites in dairy cows. Ten ruminally cannulated Holstein cows (127 ± 25 DIM; ± SD) were arranged in a 3 × 3 Latin square. Treatments were ruminal infusion of 10 mol/d of acetate as sodium acetate either over 22 h/d (CON) or over 8 h/d from 0900 to 1700 h (AM) or 2100 to 0500 h (PM). Experimental periods were 14 d with a 7-d washout period in between. Cows were milked every 6 h during the last 7 d of each period to assess the daily pattern of milk synthesis. Blood samples were taken 6 times each period to represent every 4 h over the day and plasma glucose, insulin, BHB, BUN, nonesterified fatty acids, and acetate were measured. Data were analyzed by cosinor-based rhythmometry to test the fit of a cosine function with a period of 24 h and calculate the acrophase (time at peak) and amplitude (peak to mean) of the rhythm. A 12 h harmonic model was also tested for plasma metabolites and hormones. Notably, AM increased the amplitude of milk yield by 70% and advanced the phase by 2 h and PM only advanced the phase by 1 h (P < 0.05 for all) and did not change the amplitude when compared with CON. Milk 16 carbon fatty acids fit a 24 h rhythm for AM and CON only, where AM increased the amplitude by 118% and delayed the phase by 1.6 h when compared with CON (P < 0.05). Plasma acetate fit a 24 h rhythm for all treatments. When compared with CON, AM increased the amplitude of plasma acetate by 129%, PM decreased the amplitude by 28%, and both treatments result in a phase shift (P < 0.05 for all). The rhythm of other variables of secondary interest were also affected by treatment. In conclusion, the results support a role of the timing of acetate absorption in entraining the daily rhythm of milk synthesis.