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 intravenou s administration of sodium propionate solution (1.84 mol/L) were exami ned 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 h ealthy cows than in those suffering from ketosis. Moreover, the ketoti c cows exhibited a significantly lower cortisol response commencing fr om a lower base line. While initial glucose and cortisol concentration s were positively correlated (P < 0.01) in the whole group of cows, th e size of integrated increments in glycemia and cortisol levels after propionate administration were not in correlation. However, as found i n an earlier study, the animals could be subdivided into a group showi ng a high cortisol response to propionate (n = 14) and a group showing a low responses (< 100 nmol/L at 60 minutes; n = 16). Parameters conc erning cortisol levels and glycemia were not associated in the high re sponders, indicating mutual independence of mechanisms controlling the ir values. In the low responders, ten of which were ketotic, there was a statistically significant correlation between the increment in glyc emia and cortisol after propionate administration (r = 0.576; P <0.05) . The results obtained indicate that conditions which lead to a low co rtisol status may be a predisposing factor in the appearance of sponta neous ketosis in peripartal Holstein cows.