Assessment of Prolactin and Quantitative Milk Production After Induction of Lactation in Barren Jennies (Equus asinus): A Pilot Study

The secretion of circulating prolactin levels in response to sulpiride treatment was evaluated in eight mature cyclic barren jennies divided into two groups on the basis of different treatments. The experimental group A was submitted to the sulpiride treat- ment twice a day for nine consecutive days, up to 14 days after ovulation, and the control group B was submitted to the equivalent saline placebo administration. Milking was started at 8 days after ovulation, at 3 days after the beginning of sulpiride treat- ment, to 28 days after ovulation, and performed five times per day between 09:00 AM and 11:00 PM by hand; the oxytocin treatment was performed (5 IU/head per intra- muscular injection) 5 minutes before milking, to facilitate the udder contraction. Blood samples were collected in baseline conditions (the day before the onset of the treat- ments) from day 0, during all treatment periods, until day 28 after ovulation, from the jugular vein from the each subject, twice a day, at 08:00 AM and at 08:00 PM. Both pluriparous experimental (P < .0005) and control (P < .005) jennies and nulliparous experimental (P < .005) and control (P < .0005) jennies showed higher morning prolactin (PRL) concentrations than afternoon values. Nulliparous experimental jennies showed higher morning (P < .0001) and afternoon (P < .0001) PRL values than nullip- arous control jennies. Significant and negative correlation between PRL concentrations and milk production (r 1⁄4 0.67) was observed only in experimental pluriparous jennies. The present pilot study demonstrates the PRL profiles during and after induction of lactation in barren pluriparous and nulliparous Ragusana jennies.