EFFECTS OF LUTEOLYTIC DOSES OF PROSTAGLANDIN-F2-ALPHA AND CLOPROSTENOL ON CONCENTRATIONS OF PROGESTERONE, LUTEINIZING-HORMONE, FOLLICLE-STIMULATING-HORMONE, GLUCOSE, INSULIN, GROWTH-HORMONE, THYROXINE, PROLACTIN AND CORTISOL IN JUGULAR PLASMA OF LACTATING DAIRY-COWS

Three groups of five lactating dairy cows in the mid-luteal phases of oestrous cycles were given an injection (at time 0 h) of the naturally -occurring prostaglandin F-2 alpha (PGFe(2 alpha)) or cloprostenol (a synthetic analogue of PGE(2 alpha)) at doses recommended for inducing luteolysis, or injection vehicle. Concentrations of glucose and hormon es in jugular plasma were measured from 26 h before to 12 h after the injections and the significance (P<0.05) of the effects of the prostag landins on these concentrations was determined. Both prostaglandins in duced falls in progesterone concentration and rises in luteinizing hor mone concentration; neither influenced follicle-stimulating hormone. P GF(2 alpha) increased glucose concentration; neither prostaglandin inf luenced insulin concentration. Both prostaglandins increased growth ho rmone concentration and resulted in declining thyroxine concentration. PGF(2 alpha) increased prolactin and cortisol concentration. There we re, however, no significant differences between the effects of the two prostaglandins on any hormone (or glucose) concentration.