Effects of age on follicle and hormone dynamics during the oestrous cycle in mares

Abstract

The effects of age (young: 5-6 years; intermediate: 10-14 years; old: > or =18 years) on follicle and hormone dynamics during an interovulatory interval (IOI; n = 46) and on preovulatory oocytes and concentrations of follicular fluid factors (n = 44) were studied in mares. Old mares were not approaching senescence, as indicated by regular lengths of the IOI (19-27 days) during the period May-October. The IOI was 1 day longer (P < 0.05) in the old group than in the two younger groups and was associated with a slower (P < 0.05) growth rate of the ovulatory follicle. The old group had diminished follicle activity, as indicated by significantly smaller and fewer follicles. Concentrations of FSH did not differ among age groups, except that the maximum concentration was greater (P < 0.05) in the old group. Concentrations of LH were greater (age x day interaction; P < 0.03) in the young group throughout the ovulatory LH surge and may have played a role in a shorter (P < 0.05) interval from maximum diameter of the preovulatory follicle to ovulation. Maximum circulating concentrations of oestradiol during the preovulatory surge were greatest (P < 0.05) in the young group. No effects of age were detected on oocyte morphology. Concentrations of ovarian steroids in preovulatory follicular fluid were not affected by the age of the mares, but concentrations of free insulin-like growth factor-1 were greater (P < 0.05) in the old group. The results indicate the importance of considering the potential confounding effects of age in experimental protocols and for considering age in the development of theriogenology programmes.

Abnormal Reproductive Patterns in Przewalski's Mares Are Associated with a Loss in Gene Diversity1

“…Interestingly, elevated urinary estrogen excretion persisted until after the second ovulation. There are many factors that could be responsible for double ovulations in mares, including increased sensitivity to gonadotropins, genetics, age, and season [10,11,29]. In the present study, both mares were older than 15 yr, and this finding provides incentive for further exploring the relationship between age and ovarian function.…”

The effect of mare's age on multiple ovulation rate, embryo recovery, post-transfer pregnancy rate, and interovulatory interval in a commercial embryo transfer program in Argentina

“…As the interval from PGF treatment becomes longer, the MO rate increases. This effect appears to be due to an increase in the LH concentration after PGF-induced luteolysis (Ginther et al, 2008b).…”

Influence of the month of the year in the hematological profile in carthusian broodmares

“…A second consideration could be the physical activity performed by the animals during the study period. Sexual activity in horses occurs mainly in spring and summer, decreasing in later summer and autum, and ceasing completely in winter [24]. Further, the mares could have also had greater physical activity because they stayed longer in the pasture.…”