THE EFFICACY OF MILK EJECTION INDUCED BY LUTEAL OXYTOCIN AS A METHOD OF EARLY PREGNANCY DIAGNOSTICS IN COWS

The aim of this research was to determine the accuracy and reliability of early diagnosis of pregnancy in cows using PGF2_ analogue. Namely in the case of corpus luteum (CL) presence, the release of luteal oxytocin is induced by intravenous administration of a non luteolytic dose of PGF2_. The research was performed in 30 lactating cows, 18-22 days after insemination, and three hours prior to evening milking. A teat cannula is placed in the left fore-teat. When the cisternal milk flow ceased, Dinoprost (256 _g Dinolytic) was injected in the v. jugularis. If CL was present, the alveolar milk flow (559.4±83.7 mL) started 189±18 s later and early pregnancy could be presumed. If CL was no longer functional, the milk flow did not start again and the cow was considered not pregnant. Seventeen out of 30 cows were confirmed pregnant 35 days after insemination by ultrasound and 13 were found not pregnant. The accuracy of positive results is 100% and is identical to that obtained by ELISA of milk progesterone used as a reference method. The accuracy of negative results was lower (46.1% vs. 84.6%) (p<0.05), because seven out of 13 non pregnant cows has responded to the milk ejection test. In spite of this disadvantage, the test approved as being inexpensive, rapid, and easy to interpret and is therefore very applicable, especially under field conditions. It can be applied i.e. 20 days after insemination. Progesterone rapid test from milk or by milk ejection test can be used with similar accuracy.