PROFILES OF THE HORMONES SOMATOSTATIN, GASTRIN, CCK, PROLACTIN, GROWTH-HORMONE, OXYTOCIN AND CORTISOL .2. IN DAIRY-COWS THAT ARE MILKED DURING FOOD-DEPRIVATION

This study was performed to examine how the circulating levels and the milking-induced release of the gastrointestinal hormones somatostatin , gastrin and CCK, the pituitary hormones prolactin, oxytocin and GH a nd the adrenocortical hormone cortisol were influenced by two days of feed deprivation in dairy cows. The study was made on four dairy cows of the Swedish Red and White breed. On the second day of feed deprivat ion, the daily milk yield had decreased from 21.4 +/- 1.6 to 7.9 +/- 0 .3 kg. In feed-deprived cows the circulating levels of gastrin, CCK an d prolactin decreased, while the levels of GH and cortisol increased. In fed cows, milking-induced releases of prolactin and oxytocin were d etected. The milking-induced release of prolactin and oxytocin was sma ller in feed-deprived cows compared with fed cows, while the plasma le vel of somatostatin tended (p < 0.10) to decrease in connection with m ilking in feed-deprived cows. Additionally, a milking-related release of GH was discovered in cows subjected to fasting and simultaneously t he milking-induced release of cortisol tended (p < 0.10) to increase. It is suggested that the changed basal concentrations of hormones as w ell as changed milking-induced responses in feed-deprived cows, compar ed with fed cows, is a way by which dairy cows adapt their metabolism to the availability of energy.