Preantral follicular development in Massese lambs born during two seasons of the year

The aim of this work was to evaluate the influence of season of birth on the development of the preantral follicular population in Massese lambs. The ovaries of 30 lambs (15–30 days old) were collected at a local slaughterhouse from May to June (M–J) (n = 15) and from October to November (O–N) (n = 15). The research was conducted in Tuscany (Italy), a region characterized by a Mediterranean climate, with a nutritional and photoperiodic peak in the spring (March–June) and a decrease during summer–autumn (August–November). The lamb ovaries were submitted to quantitative and qualitative hystological analyses. Results in the M–J group showed an increase of primary follicles (P < 0.05), and a lower number of primordial populations, compared to the O–N (P < 0.05) group. In the O–N group, qualitative analysis showed a significant (P < 0.05) reduction in follicle size, oocyte size and number of granulosa cells, in the primary and secondary follicle classes, when compared to the M–J group. It was concluded that the autumn season of birth negatively affected the preantral follicular population in Massese lambs. © 2004 Elsevier B.V. All rights reserved