Shifting Eating Time Alters Rumen Dynamics in Once-daily Fed Dairy Cows

Abstract

e objective was to establish e�怆ects of providing a total mixed ration (TMR) at either 0900 h or 2100 h on rumen fermentation and passage kinetics, and microbial protein biomass in lactating cows. Four multiparous and four primiparous Holstein cows were used in a cross- over design study with two 6-week periods, each with 3-week adaptation. Total urine was collected during a sampling week in each period to measure urinary excretion of purine derivatives to estimate microbial protein biomass. Rumen ammonia concentrations were lower in primiparous cows fed at 2100 h vs. 0900 h (10 vs. 11 mg/L, P<0.05). Rumen propionate was lower (26.5 vs. 28 mmol/L) and the acetate to propionate ratio was higher (2.1 vs. 1.9) in multiparous cow fed at 2100 h vs. 0900 h. Microbial protein estimates were not sgnficnty ��怆ected by eating time. Evening fed cows tended to realize a greater rumen volume than morning fed cows (107 vs. 90 L, P<0.01). �䀆erefore, feed delivery at 2100 h vs. 0900 h increased rumen volume and fermentation without sgnficnty ��怆ectng microbial protein synthesis.