Characterization of the estrous cycle of Asinina de Miranda jennies (Equus asinus)

Abstract

This study aims to characterize the estrous cycle of Asinina de Miranda jennies in the breeding season, on the basis of data collected from serial ultrasonographic examination and serum progesterone determinations in 14 females during a total of 33 cycles. The length of the interovulatory interval was 23.8 ± 0.55 days, the diestrus and estrus lasting 17.9 ± 0.46 days and 6.65 ± 0.30 days, respectively. Age and body condition score (BCS) affected the length of the interovulatory intervals; BCS also influenced the diestrus length and the time in heat after ovulation (P > 0.05). The incidence of single, double, and triple ovulations was 57.58%, 36.36%, and 6.06%, respectively. Multiple ovulations affected neither the length of the interovulatory interval nor the individual cycle stages (P > 0.05) but lengthened the interval from the beginning of estrus to the last ovulation (P = 0.01). When combined with age, higher BCS affected the ovulation rate (P = 0.001). Deviation of the dominant follicle occurred around Day 8.7 (Day 0 = ovulation) when both single and multiple ovulations were considered. The dominant follicle was larger at divergence in single ovulators (19.18 ± 0.97 mm) compared with that in multiple ovulators (18.05 ± 1.16 mm). The overall maximum follicular diameter before ovulation was smaller in multiple ovulatory cycles than that in single ovulatory cycles (37.2 ± 0.83 mm vs. 40.2 ± 1.41 mm, respectively; P = 0.03). The daily growth rate of dominant follicles was independent of the ovulation rate (P > 0.05) for the intervals before and after the estrus onset. The dominant follicle size and the follicle growth rates were independent of BCS (P > 0.05). Data collected in this study revealed resemblances between Mirandese and other Iberian and Brazilian breeds with regard to estrous cycle characteristics.

Reproductive Patterns in the Non‐Breeding Season in Asinina de Miranda Jennies

“…For progesterone (P4) measurements, blood samples were collected and processed as previously described by Quaresma and Payan-Carreira (2015). In short, the samples were obtained by venipuncture of the jugular into serum-gel tubes (S-Monovette Ò ; Sarstedt, Nümbrecht, Germany).…”

The Potential for New Donkey Farming Systems to Supply the Growing Demand for Hides

“…In recent years, information on donkey reproduction has improved due to an increased interest in donkey breeding, mainly in Europe and the Americas. Nevertheless, compared to Animals 2020, 10, 718 4 of 22 horses and other domesticated animals, knowledge about the reproductive physiology of donkeys and donkey breeding management is still very limited [34][35][36][37][38][39][40]. In addition, intensive donkey farming is a relatively recent development, mainly for the production of donkey dairy products in Europe and for donkey hides but also meat and dairy in China [23,34,[41][42][43][44][45].…”

“…It is likely that conception rates in a (less controlled) large-scale farming system will be lower. On the other hand, in the literature, conception rates are often defined by the oestrous cycle, which is approximately 25 days for most donkey breeds studied [39]. The model defines the conception rate on a monthly basis.…”

“…Multiple ovulations are common in donkeys. The percentage of multiple ovulations reported are between 5 and 70 percent [39]. Yang et al [56] find that depending on the season, 16 to 34 percent of Dezhou black donkey jennies experience double ovulation.…”

“…Donkeys enter puberty between 1 and 2 years of age [36,51]. In many research studies, the youngest breeding animals included are two or three years of age [34,35,38,39,[53][54][55][56]. The oldest animals in the non-Chinese studies are often between fifteen and twenty years but, for the two Chinese research studies, the oldest jennies were seven and ten years [54,56].…”