Factors influencing the oestrus cycle of Arab mares

This work aims to study the factors of variation of the oestrous cycle of Arab thoroughbred mares under the conditions of northern Tunisia. The duration of the oestrous and of the oestrus cycle of 182 mares naturally bred (NB, n=152) and undergoing artificial insemination (Al, n=30) were monitored daily from February to May during 2017 breeding campaign. The reproductive status of mares, their parity and the rank of the oestrous cycle were studied in function of the duration of the oestrous cycle and the oestrus. Results showed that the duration of the oestrous cycle was longer in maiden mares than in the lactating and in the barren ones (p<0.05). Moreover, this parameter was shorter starting from the 4th cycle for the mares conducted in NB (p<0.05), and longer during the 3rd cycle in Al mares (p<0.05). In addition, the duration of oestrus was shorter in older mares (p<0.05). It is interesting to notice that the oestrous cycle and oestrus durations decrease as the breeding season progresses (p<0.05). This work establishes, in conclusion, that the durations of the oestrous cycle and the oestrus in the Arab thoroughbred mares raised in northern Tunisia did not vary in the same way depending on the factors studied. Only reproductive status, cycle rank and the month of the breeding season affect the length of the oestrous cycle. In contrast, oestrus duration was affected only by the age of the mare and the month of the breeding season.