Resumen
- We previously reported that propionic acid (P) reduced dry matter (DMI) and metabolizable energy intake compared with glycerol (G) when administered as isoenergetic infusions to the abomasum of cows in the postpartum (PP) period. Our objective in this experiment was to evaluate short term effects of P compared with G on hepatic acetyl CoA (AcCoA) content for PP cows. We hypothesized that P compared with G will decrease the AcCoA content in the liver within the time frame of a meal. Six ruminal cannulated cows in the PP period (15.2 ± 7.7 d PP) were used in a crossover design experiment to evaluate the effects of G and P pulse dosed to the abomasum on hepatic AcCoA content and plasma concentrations of metabolites and hormones. Cows were randomly allocated to treatment sequence (G P and P G) and each block was completed in 3 d with 2 collection days and a rest day between them. Two moles of P or G (2 mol/500mL, ≥ 99.5%) were dosed within 1 min to the abomasum 1 h before feeding. Liver tissue was biopsied and blood was collected immediately before dosing and at 30 and 60 min after dosing. Treatments interacted with time to affect AcCoA content (P < 0.01). At 30 min after dosing, P decreased AcCoA content by 34% while G increased AcCoA content by 32%, resulting in differences in AcCoA for P compared to G at 30 min (18.0 vs. 36.9 nM/g, P < 0.0001), which persisted at 60 min after dosing (21.9 vs. 32.8 nM/g, P < 0.01). Plasma BHBA concentration decreased and glucose concentration increased over time for both treatments (P < 0.001). While plasma NEFA concentration tended (P = 0.059) to be lower for P compared with G at 30 min, it was numerically higher by 60 min when hepatic AcCoA content was still lower. Therefore, the reduction of hepatic AcCoA content by P compared with G was likely because of oxidation in the tricarboxylic acid cycle. This is consistent with these treatment effects on DMI according to the Hepatic Oxidation Theory.