Abstract
The present study was conducted to detect the ovarian activities of mares using ultrasonography in relation to the different seasons of the year under Egyptian environmental conditions. This study was carried out on 465 clinically healthy and non-lactating mares. The animals were cyclic and showed signs of estrus regularly. The experimental period was extended from January 2014 to December 2016. All mares were examined with ultrasonography for determination of the reproductive status of each mare specially the degree of activity of the two ovaries monthly. The degree of ovarian activity was either inactive or active according to size of follicles. The results were illustrated that the highest ovarian activity of mares was extended from March till July. On contrary, during November, December and January mares were had higher percentages of smooth ovaries than other months throughout the year. In relation to the season, the highest ovarian activity was reached late spring and early summer while, the least ovarian activity was in late autumn and early winter with minimal ovarian activity in winter season. Ovarian activity in mare was found all over the year with the highest ovarian activity in spring and summer and the lowest ovarian activity in autumn and winter. It was concluded that under Egyptian conditions, most mares have the ability to show continue cycling activity throughout the year, however, photoperiod play an important role in the intensity of ovarian activity and reproductive cycle.
Highlights
The mare is seasonally polyestrus, with estrus cycles beginning in mid to late winter and continue throughout the early fall (Colquhoun et al, 1987; Ginther, 1992 and Williams et al, 2012)
Mares that had the highest percent of large follicles were recorded during spring while the highest percent of small follicles were observed in mares with inactive ovaries during winter, where there were almost no large follicles (Table 2)
Trans-rectal ultrasonography is a good tool for determination of ovarian activity in mare
Summary
The mare is seasonally polyestrus, with estrus cycles beginning in mid to late winter and continue throughout the early fall (Colquhoun et al, 1987; Ginther, 1992 and Williams et al, 2012). Mares exhibit estrus behavior during the anovulatory period and this is probably due to the release of estrogenic steroids from the adrenal cortex (Sharon and Crowell-Davis, 2007). Some mares would show behavioral signs of estrus, throughout the year, that may be accompanied by ovulation (Hafez and Hafez, 2000; Nie, 2007). There are many factors that influence estrus cycle in mares such as season, age, Assiut Vet. Med. The present study was conducted to detect the ovarian activities of mare using ultrasonography in relation to the different seasons of the year
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