605
Propionic Acid Decreased Meal Size and Feed Intake Compared with Glycerol when Infused Abomasally in Cows in the Postpartum Period
Our objective was to evaluate effects of propionic acid (P) and glycerol (G) on dry matter intake (DMI) and feeding behavior for cows in the immediate postpartum period. We hypothesized that propionic acid will decrease DMI and meal size compared to glycerol because of differences in their hepatic metabolism. Isoenergetic infusions of P or G were administered abomasally to eight ruminally cannulated multiparous Holstein cows (4.8 ± 2.3 DIM) in a double crossover design with four, 2-day infusion periods. Treatment sequences (P-G-P-G or G-P-G-P) were assigned alternately to cows based upon date of parturition. Treatments were propionic acid (99.5%, 1.00 M) and glycerol (99.7%, 0.92 M) infused at 483 ml/h, which provided 4.26 Mcal/d. Feeding behavior was recorded by a computerized data acquisition system. Data were averaged within period, and period means were analyzed by analysis of variance; the model included the random effect of cow, the fixed effects of period and treatment, and interactions between treatment and period and between treatment and cow. No difference was detected for the amount of each treatment infused (11.6 L/d). Propionic acid decreased DMI 16.7% compared with glycerol (12.5 vs. 15.0 kg/d, P = 0.04) by decreasing meal size (1.04 vs. 1.18 kg DM, P < 0.05). No interaction was observed between treatment and period indicating a sustained treatment effect over time. Propionic acid tended to increase the time between meals 35 min (114 vs. 79 min, P = 0.11) but did not affect meal frequency (12.3 meals per d; P = 0.48) compared with glycerol. Propionic acid decreased the hunger ratio (meal size to time since the previous meal) by 25% compared with glycerol (20.3 vs. 27.1 g/min, P = 0.05) as well as the satiety ratio (meal size to time until the next meal) by 27% compared with glycerol (24.6 vs. 33.6 g/min, P < 0.02). Consistent with our hypothesis, propionic acid decreased meal size and DMI compared with glycerol possibly because of differences in their metabolism in the liver.
Keywords: fresh cows, feed intake, hepatic metabolism