Impact of birth season on puberty in female and male kids of Shami goat in North Sinai, Egypt [electronic resource].

Includes reference.

This study was carried out to determine the effect of season of birth on puberty in female and male Shami kids. Three groups of each sex born in winter, spring and autumn were observed. During these seasons, both males and females were weaned at 90 days old and offered ad libitum berseem (Trifolium alexandrinum) hay plus 100g/ headl day of concentrate feed mixture (14 % protein). In female kids, the onset of ovarian activity was detected by plasma progesterone (P4) concentration determined once a week from 3 to 6 months of age then twice weekly until the onset of puberty. The results showed that, season of birth had significant (P< 0.01) effect on the age at first ovulation (puberty). Ovarian activity commenced at significant earlier age (201 ±23.1 days) in spring born female kids compared with either winter (264±56.9 days) or autumn (344±65.1 days) born female kids. However, there was no fluctuation in the level of P4 except a small rise (low peak) observed a few days before the onset of puberty. The P4 remained at the basal level of 0.24 ng/ml till the day of estrus and then increased gradually to the peak level of 6.4 - 8.7 ng/ml at day 10-11 of the cycle, which persisted for the next 4-5 days and then declined to the basal level at the end of the estrous cycle (day 20). Sings of estrous behaviour were observed on the day of estrus. In male kids, the onset of puberty was individually recorded by observing the ability of the male kids to mount and copulate the induced estrus goat does. The presence of immobile spermatozoa in the ejaculate was obtained by an artificial vagina after one week of the first mount. The results showed that, season of birth had significant (P< 0.01) effect on the age at the first mounting. The pUberty age of male kids born in spring (111±3.0 days) and autumn (112±5.0 days) was attained significantly (P < 0.01) earlier than those born in winter (131±4.0 days).

Summary in Arabic.

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