The pituitary and testicular responses to GnRH challenge between 4 and 14 months of age in thoroughbred colts born in spring and autumn.
Anim Reprod Sci
; 88(3-4): 287-98, 2005 Sep.
Article
em En
| MEDLINE
| ID: mdl-16143218
ABSTRACT
Gonadotropin releasing-hormone analogue (buserelin) challenges were carried out every 8 weeks from 4 to 14 months of age on thoroughbred colts born in the spring (n = 6) or autumn (n = 5) to define the onset of puberty. In all colts, luteinizing hormone (LH) secretion followed a seasonal pattern, with high baseline and maximal concentrations in the spring and summer and low concentrations in the winter. Testosterone concentrations were undetectable before spring and, thus, autumn-born colts were younger than spring-born colts when a testosterone response to buserelin was first observed. Mean weights of the autumn-born colts were 300 kg (282-327 kg) at the time of the first detectable testosterone response in the following spring (October). Spring-born colts had reached this weight in the winter (May and June, before day length had increased) but did not exhibit a significant testosterone response until the spring at a mean weight of 352 kg (327-403 kg). It is proposed that colts must achieve a threshold body weight concurrently with stimulatory photoperiod for onset of puberty to occur.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Hipófise
/
Estações do Ano
/
Testículo
/
Envelhecimento
/
Busserrelina
/
Cavalos
Limite:
Animals
Idioma:
En
Revista:
Anim Reprod Sci
Ano de publicação:
2005
Tipo de documento:
Article
País de afiliação:
Nova Zelândia