Characteristics of follicular dynamics and reproductive hormone profiles during oestrous cycles of jennies over an entire year

Abstract

Although donkeys have been domesticated for over 6,000 years, limited information is available concerning their reproductive physiology, especially under intensive rearing conditions. The aims of this experiment were to study follicular dynamics and reproductive hormone variation in jennies during the inter‐ovulatory interval in different seasons. A total of 12 continuous cycles of six Dezhou Black (DB) donkey jennies were examined in four different seasons. The diameters of the six largest follicles of each jenny were measured daily by ultrasonography, and blood samples were collected at fixed times for reproductive hormone assays. The results demonstrated that most jennies displayed regular oestrous cycles in all seasons. The follicular dynamics were similar in Spring, Summer and Winter, while the jennies had longer oestrous cycles with delayed follicular deviation and dominant selection in Autumn. At least two follicular waves were observed in each oestrous cycle, throughout the study, but two jennies presented oestrous cycles with three follicular waves in the Autumn. The numbers of follicular waves were consistent with the numbers of FSH surges. Oestrous characteristics of the jennies in a large herd were also analysed. The results showed that the rates of regular oestrous cycles were 83.1% (265/319), 89.6% (215/240), 80.2% (235/293) and 77.1% (178/231), with 26.4% (70/265), 19.5% (42/215), 22.1% (52/235) and 23.0% (41/178) double ovulation rates in Spring, Summer, Autumn and Winter, respectively. The results presented may be useful for donkey farms in the design of breeding strategies.

Follicular dynamics during the non‐reproductive season in Miranda jennies

“…The observation of an anoestrous period in 5/12 jennies was in contrast with Li et al. (2021) results, who did not detect periods of anoestrus in Dezhou Black jennies, in a more homogenous population in terms of body conditions and age. The jennies used by our group presented significant BCS and age variations, factors known to affect anoestrous presentation (Quaresma et al, 2015).…”

“…The four-wave cycles, albeit uncommon, were a novel finding, and its observation was limited to the autumn. The incidence of more waves in this period was also reported byLi et al (2021).…”

“…In the present study, the only sex steroid hormone measured with the number of FSH surges within an IOI (Li et al, 2021), as observed in mares (Ginther, 1993). Nevertheless, in this study, we did not observe differences in the number of waves detected between autumn transition, winter anoestrous or spring transition.…”

“…Li et al (2021) described the predominance of the two-wave pattern in jennies' oestrous cycle, as it was observed byGastal et al (1999) in ponies andOj et al (2000) in mares. Our results also point to a predominant two-wave pattern (70%), but the prevalence of the three-wave cycles reached 24.6%.…”

“…(2003) in posterior studies of mares’ oestrous cycle and women menstrual cycle respectively. An adaptation of this non‐identity method of identifying follicular waves was recently used for jennies (Li et al., 2021). Briefly, the method involved measuring and sorting all follicles larger than 5 mm, in descending order of diameter, for each jenny on each day of measurements.…”