Diurnal Rhythm of Plasma Oxytocin Concentration in Lactating Buffalo Cows

Abstract

The aim of this study was analyze the diurnal rhythm of plasma oxytocin (OT) concentration in lactating buffalo cows during autumn and spring. Data were obtained from 10 females in May (autumn) and 10 females in September (spring) at 3-h intervals for 3 consecutive days. Cosinor and spectral analyses showed that, in autumn, 30-40% of the animals showed a significant 24-h rhythm of plasma OT concentration, whereas in spring the animals did not present a diurnal rhythm of plasma OT concentration. The majority of the acrophases for OT in autumn occurred at early morning and morning while in spring it was distributed along the day. Our study shows that diurnal rhythm of plasma OT concentration was more evident in some animals in the autumn that in the spring, what may suggest that photoperiod among others factors can influence in this response.