THE INFLUENCE OF SODIUM PROPIONATE ON BLOOD-GLUCOSE AND SERUM CORTISOL CONCENTRATIONS IN HEALTHY AND SPONTANEOUSLY KETOTIC LACTATING COWS

Changes in glycemia and serum cortisol concentrations after intravenous administration of sodium propionate solution (1.84 mol/L) were examined in lactating Holstein dairy cows. Propionate was given as a single dose after milking and feeding to a group of fifteen healthy cows and an equivalent group of fifteen cows showing clinical signs of ketosis between 7 and 14 days after calving. Although very large differences were found between individual animals for both parameters at each time interval, it was established that initial glucose concentrations and the glycemic response to propionate were considerably greater in the healthy cows than in those suffering from ketosis. Moreover, the ketotic cows exhibited a significantly lower cortisol response commencing from a lower base line. While initial glucose and cortisol concentrations were positively correlated (P < 0.01) in the whole group of cows, the size of integrated increments in glycemia and cortisol levels after propionate administration were not in correlation. However, as found in an earlier study, the animals could be subdivided into a group showing a high cortisol response to propionate (n = 14) and a group showing a low responses (< 100 nmol/L at 60 minutes; n = 16). Parameters concerning cortisol levels and glycemia were not associated in the high responders, indicating mutual independence of mechanisms controlling their values. In the low responders, ten of which were ketotic, there was a statistically significant correlation between the increment in glycemia and cortisol after propionate administration (r = 0.576; P <0.05). The results obtained indicate that conditions which lead to a low cortisol status may be a predisposing factor in the appearance of spontaneous ketosis in peripartal Holstein cows.