Abstract #M307

# M307
Effects of temporal supply of propionic acid on feeding behavior of cows in the postpartum period.
G. Maldini*1,2, M. S. Allen1, 1Michigan State University, East Lansing, MI, 2CAPES, Brasilia, DF, Brazil.

Appetite suppression during the postpartum (PP) period is likely caused by a signal related to hepatic oxidation of fuels. Faster absorption and hepatic uptake of propionate is expected to accelerate hepatic oxidation, stimulating satiety sooner, reducing meal size. However, if excessive propionate absorption from the rumen results in less efficient hepatic extraction of propionate, effects on meal size might diminish and hepatic oxidation following meals might be extended decreasing meal frequency. The objective of this study was to determine the temporal effects of propionic acid (PA) infused intraruminally at initiation of meals on feeding behavior. Eight ruminally-cannulated, multiparous cows in the PP period were utilized in a 4x4 Latin square design experiment. Cows were blocked by parturition and randomly assigned to treatment sequence within square. Treatments were infusion of 1.25 (HIGH) or 0.5 mol (LOW) of PA at initiation of meals over 5 min (FAST) or 15 min (SLOW). Infusions were triggered at each meal for 12 h. A 24-h recovery period was allowed between infusion days to reduce carry-over effects of treatment. HIGH decreased DMI compared with LOW (7.2 vs 11.2 kg/12 h, P = 0.001) by decreasing meal frequency (5.8 vs 7.5 meals/12 h; P = 0.02). HIGH decreased eating time (103 vs 127 min/12 h, P = 0.002) and reduced eating rate (52 vs 66 g/min; P < 0.01) compared with LOW but did not affect meal size (P = 0.38). FAST increased meal length compared with SLOW (28.2 vs 22.7 min; P = 0.05) but tended to decrease eating time (109 vs 122 min/12 h; P = 0.06) and did not affect meal size (P = 0.68) or meal frequency (P = 0.16). No interactions of treatments were detected for DMI or feeding behavior parameters (P > 0.32). Treatment effects on milk yield were not detected. The lack of effect of infusion rate on meal size, along with the reduction in DMI by HIGH compared with LOW by decreasing meal frequency rather than meal size, suggests that propionate flux to the liver might have exceeded the liver’s capacity for first-pass extraction of propionate from the blood, likely extending hepatic oxidation longer after meals for the higher propionate dose.

Key Words: liver metabolism, feed intake, oxidation of fuels