Role of ovarian failure in reproductive senescence in aged red deer (Cervus elaphus) hinds

Physiological and endocrine factors associated with reproductive senescence were assessed in a group of 19 ageing red deer kinds. Reproductive success , defined as the percentage of hinds weaning a calf successfully, decreased gradually from 89% at 6-7 years of age to 50% at 17 years, and subsequentl y decreased markedly; only one hind reared a calf at 19-20 years of age. Wh en the 12 surviving hinds were approaching 21 years of age, they were compa red with ten mature 7-year-old females over the onset of the breeding seaso n. All hinds were subsequently killed, the reproductive tracts were recover ed and antral (greater than or equal to 2 mm in diameter) and preantral fol licle populations were determined by dissection (n = 7 hinds per age group) or stereological analysis (n = 2 ovaries per age group), respectively. Cyc lical ovarian activity (plasma progesterone) was evident in fewer aged hind s compared with mature hinds (3/12 versus 10/10, P < 0.001) and mean plasma LH concentrations were higher in aged animals than in mature animals (0.57 +/- 0.05 and 0.20 +/- 0.05 ng ml(-1), P < 0.001). Mean uterine (44.2 +/- 4 .5 and 75.4 +/- 4.2 g; P < 0.001) and ovarian masses (0.88 +/- 0.11 and 1.5 2 +/- 0.12 g; P < 0.001) were lower in the aged hinds, which also had fewer antral follicles than did mature hinds (0.89 +/- 0.35 and 23.5 +/- 4.5 fol licles per hind, respectively; P < 0.001). Only one primordial follicle was observed in one of the ovaries of the aged hinds, compared with 7000-21000 in the ovaries of mature kinds. The high gonadotrophin concentrations, pau city of primordial and antral follicles and failure of ovulation indicate c ollectively that waning reproductive performance after 17 years of age is p rimarily due to ovarian failure.