Effects of acetic acid or sodium acetate infused into the rumen or abomasum on feeding behavior and metabolic response of cows in the postpartum period

Abstract

Effects of continuous isomolar infusions of acetic acid (AcA) or sodium acetate (NAc) infused into the rumen (RU) or into the abomasum (AB) on feeding behavior, dry matter intake (DMI), and metabolic response of cows in the early postpartum period were evaluated. Six rumen-cannulated multiparous Holstein cows (11.8 ± 3.9 d in milk; mean ± SD) were utilized in a 6 × 6 Latin square design experiment balanced for carryover effects with a 2 × 3 factorial arrangement of treatments. Treatments were AcA and NAc, with sodium chloride (CON) as a control, infused at a rate of ˜0.75 mol/h (0.5 L/h) into the RU or AB for the first 8 h following feeding, with a rest day between infusion days. Treatment sequences were assigned randomly to cows. Feeding behavior was recorded by a computerized data acquisition system and blood was sampled at 0, 4, and 8 h relative to the start of infusion. We hypothesized that AcA is more hypophagic than NAc, and that infusion into the AB is more hypophagic than infusion into the RU. Dry matter intakes (DMI) for the CON treatments were similar at 6.2 kg/8 h for RU and 6.1 kg/8 h for AB, and the AcA and NAc treatments interacted with site of infusion to affect DMI. The NAc-RU treatment did not reduce DMI (7.0 kg/8 h), whereas AcA-RU (2.6 kg/8 h), AcA-AB (3.7 kg/8 h), and NAc-AB (4.0 kg/8 h) decreased DMI compared with CON. Following infusions of AcA compared with NAc, there was a residual effect on DMI for the remainder of the day, but treatments did not affect DMI during the rest day. Treatments increased plasma acetate and β-hydroxybutyrate concentrations over time (interaction) and decreased plasma insulin concentration compared with CON. Plasma glucose concentration decreased over time after AcA-AB infusion compared with other treatments and CON. Plasma nonesterified fatty acid concentration increased over time for AcA compared with NAc and CON, suggesting an increase in lipolysis to compensate the decrease in DMI. In contrast to the other treatments, NAc-RU did not decrease DMI compared with control but we cannot determine the reason for this from the data available from the current study.