The effect of exogenous oxytocin on milkability and milk composition in ewes differed in milk flow pattern

Abstract

During milking routine in sheep, the cluster is attached without pre-stimulation and milk ejection occurred (or not) as a consequence of liner movement on teat. The goal was to describe the importance of milk ejection before cluster attachment on milk flow patterns, milk composition and other parameters of milkability of ewes with two different physiological responses to usual milking (ewes with one emission of milk, i.e. expected no milk ejection (1P) and ewes with two emissions of milk i.e. expected milk ejection (2P)). On the base of three pre-experimental consecutive milkings, 22 adult lactating dairy ewes of two breeds Tsigaj (n=11) and Improved Valachian (n=11) were selected from the herd of experimental farm of APRC Nitra for this study. The animals were divided into two groups (first group 1P – ewes, and second group 2P – ewes). Ewes were regularly milked two times a day. Milk flow data were recorded during two evening milkings with 48h in between. During the first measurement the half of the animals in each group was treated by 5UI i.m. of oxytocin (OT) and the second half by physiological saline (SA) 60s before the cluster attachment. The application of OT and SA in both groups was changed in cross-over design during the second evening milking. Milk flow kinetics were recorded individually using an electronic jar with 2-wire compact magnetostrictive level. The OT treatment caused shortening of the milking time, increasing of peak milk flow rate and milk yield in thirty seconds in both groups. There were not any changes in milk composition in 2P ewes between SA and OT treatment. In 1P ewes, there was significantly increased total milk yield, machine milk yield, peak flow rate, milk yield in thirty and in 60s in OT treatment. Moreover, the increased fat yield was recorded in 1P group after OT treatment only. In conclusion, milk ejection occurrence before cluster attachment influences differently the milkability and milk composition in ewes differed in milk flow patterns during usual milking. Thus milk ejection is crucial in our breed for milk yield and composition recording.