Seasonal effects on fertility and ovarian follicular growth and maturationin camels (Camelus dromedarius)

Camels are said to be seasonal breeders, but the extent to which season int erferes with food supply to affect ovarian function is not fully documented . Hence, the three aims of this study were: (1) to define the breeding seas on of camels maintained in semi-arid conditions in southern Morocco; (2) to relate the proportion of females with active ovaries (i.e., with follicles > 5 mm), with ovulatory (11-17 mm) or cystic (> 18 mm) follicles to age an d body conditions score; (3) to study the consequences of the interactions between age and body conditions score on the proportion of females ovulatin g and conceiving; and (4) to compare follicular maturation, using in vitro steroidogenesis by intact follicles as a marker during the transition into the breeding season (October) and peak breeding season (March). There was a clear breeding season in the two flocks studied, since over 80-90% of the matings occurred during the period from mid-November to mid-April. Collecti on of ovaries at slaughter (n = 238) demonstrated a significant seasonal ef fect on the proportion of females with active ovaries (increasing from 73.5 % in October-December to 89% in January-May), but no changes in the proport ion of females with ovulatory follicles. Lean females (BCS < 2.5) had a del ayed initiation of ovarian function in October-December. In addition, the p roportion of females with cystic follicles was also affected by season (pea king during April-May). Neither age nor body condition modulated the freque ncy of cysts. Finally, the proportion of females conceiving increased stead ily as season progressed (peaking at 57% in April-May). Body condition scor e did not affect this proportion, but young females (less than or equal to 5 years old) had a low ability to conceive. Morphological features of large follicles were unaffected by season. Ovulatory follicles contained around 10(7) granulosa and theca cells. In vitro testosterone output by intact fol licles was unrelated to follicle size and season. In vitro oestradiol outpu t increased with increasing follicle size and was larger in follicles obtai ned during peak breeding season than at its initiation. This may indicate t hat early breeding season follicles display a low aromatase activity in the ir granulosa cells. Whether the low oestradiol output of early breeding sea son follicles is resulting in the low fertility observed at this period rem ains to be determined. (C) 1999 Elsevier Science B.V. All rights reserved.