OXYTOCIN RELEASE AND MILK EJECTION PARAMETERS DURING MILKING OF DAIRYEWES IN AND OUT OF NATURAL SEASON OF LACTATION

Two groups of 40 milking Lacaune ewes were monitored during their natu ral (spring) and off-season (autumn) lactation. Serial samples collect ed before, during and after milkings were used to study oxytocin relea se in relation to milk flow patterns recorded during milking. Overall, oxytocin release was significant in 92.5% of the ewes but only 56% of them exhibited clear alveolar milk ejection. Oxytocin is essential fo r milk ejection but no correlation between oxytocin ejection and milk fraction volumes of milking was detected. Baseline oxytocin and proges terone concentrations and the proportion of cisternal milk were signif icantly higher in autumn than in spring. It was concluded that clear a lveolar emission of milk during milk flow recordings are not reliable indicators of milk ejection efficiency in high producing animals with large cisternal volumes. Likewise, the amount of oxytocin released dur ing milking cannot be used to select the animals best adapted to machi ne milking or the best producers. Nevertheless, this study suggests th at luteal oxytocin has a major role in milk transfer between milkings. (C) 1998 Elsevier Science B.V.