This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Caillol, M. Articles by Rossano, B. Search for Related Content PubMed Articles by Caillol, M. Articles by Rossano, B.

Influence of season of birth on onset of gonadotrophic and ovarian functions in young doe hares (Lepus europaeus)

Summary. The pituitary and ovarian responses to a monthly i.v. injection of 5 pg luteinizing-hormone-releasing hormone (LHRH) were studied in three groups of young doe hares, born in January–February (group I), in April (group II) or at the end of the breeding season (August–September, group III). The LHRH injection was always followed by a release of LH and progesterone, which did not differ among the three groups at 3 months of age. The pituitary and ovarian responses to LHRH increased gradually from the age of 3 months in groups I and III and from the age of 9 months in group II. One female of the ten born in January–February ovulated and reached puberty in June, at the age of 4 months, but with a weak pituitary response. The females born in April displayed a seasonally delayed puberty, at 9 months of age (two of five females ovulated in the next January). Four of the five females born at the end of the breeding season ovulated after LHRH when 5 months old (in February), with a full pituitary–ovarian response. The low pituitary response of group I in June–August, even if 10–20% of females ovulated after LHRH, suggests a need for a period of short days. Then, the most favourable conditions for the hare to reach puberty would be a period of short decreasing daylengths during the fall, followed by increasing daylengths after the winter solstice.

Keywords: brown hare; season of birth; puberty; LHRH; LH; progesterone; ovulation