No abstract

No abstract

(fig. 7). 3. The cyclic changes in the milk ejection parameters caused by PGF 2 Πwere closely related to the plasma progesterone level (figs. 2, 3, 5, 6). The coefficients of correlation between the progesterone level and the -threshold dose : r = -0.809 ** (group AI, -volume of ejected milk : r = + 0.872 *** (group B), -deflection amplitude : r = + 0.805*!&dquo;!&dquo; (group B) were always significantly higher than the threshold of 0.001.Various hypotheses concerning the endocrine control of cyclic variations in milk letdown under the effect of PGF 2 Πare discussed.Introduction.

Summary. The (fig. 4).After D15, the increase in intramammary pressure progressively weakened and became 0 at D17 in the cyclic ewes, whereas in the pregnant animals there was a renewed increase in intramammary pressure until D20 ; this regressed progressively afterwards and disappeared towards D45. This transitory, renewed activity between D1 5 and D20 might be an indirect or direct result of the message delivered by the embryo to maintain the corpus luteum. Several hypotheses are discussed with a view to explaining this phenomenon.Introduction.

fig. 2).These responses were assumed to result from the release of luteal oxytocin and it is suggested that a single injection of 256 pg of Dinolytic on D20, together with milk ejection control using a teat probe, would be a rapid, little expensive method for the farmer (without risks of luteolysis) (trial 2 and fig. 3) to distinguish between pregnant and non pregnant cows.Introduction.