Variation of Physiological and Behavioural Parameters during the Oestrous Cycle in Mares

Abstract

The behaviour of oestrous mares is well-known in horse breeding. However, alterations in their physiological and behavioural indices during the whole oestrous cycle are scarcely known. The objective of the study was to analyse changes in cardiac activity variables, rectal and superficial temperatures, behaviour towards humans and conspecifics, and the time of standing and locomotor activity in mares during their oestrous cycle. Fifteen adult mares in oestrus were examined in the morning and evening (six successive days) and in dioestrus (five days—once every third day). The oscillation of physiological and behavioural variables accompanies changes in mares’ sexual behaviour. Most physiological variables studied in oestrus indicate the elevated activity of the adrenergic nervous system and, opposite to that, both behaviour towards humans and conspecifics and the time of standing relate to a relaxed state. The end of oestrus, manifested by a rapid decrease in most of the physiological variables studied, is followed by changes of behavioural variables at the beginning of dioestrus. The time of locomotor activity arises at the end of oestrus. The outcomes may contribute to the knowledge of, among others, mare owners who evaluate the oestrus by mares’ sexual behaviours without regarding other rhythmically changing variables.

Follicular Dynamics and Pregnancy Rates during Foal Heat in Colombian Paso Fino Mares Bred under Permanent Grazing

“…In contrast, physiological variables decreased at the end of estrus, indicating a decrease in sympathetic activity [ 25 ]. In addition, in a study in which the authors evaluated metabolites related to stress and inflammation in the serum of mares during the perinatal period, the authors concluded that under normal perinatal conditions where mares suffer no disturbances in health during pregnancy, foaling, and lactation, there could be improved and reproductive performance [ 43 ]. In our study, these factors are likewise reduced in free-ranging and permanent grazing systems.…”

“…Studies also reported lower pregnancy rates if mares were bred at the foal heat compared to the second postpartum heat [ 19 , 20 ]. The results of these reports could be related to stressful conditions [ 43 ], impaired uterine involution, or uterine infection.…”