A. Sechman et al., EFFECT OF CGNRH-I ON THE PLASMA THYROID-HORMONES LEVEL IN THE DOMESTIC HEN DURING GROWTH SAND SEXUAL-MATURATION, Archiv fur Geflugelkunde, 62(4), 1998, pp. 183-187
The effect of chicken GnRH-I on plasma level of thyroid hormones (T-4
and T-3) was investigated in chicken during last phase of sexual matur
ation and the initial period of egg-laying. Synthetic cGnRH-I Tvas inj
ected at 15 week of pullers age at doses 35 mu g/bird or 20 mu g/bird
for 3 or 5 consecutive days, respectively. The injections were carried
out at 09:00 hr every day. Blood samples were collected at 16, 18, 20
and 22 week of age, and T-4 and T-3 were measured by RIA methods. Dur
ing sexual maturation in chicken a gradual decrease in plasma T-4 and
T-3 concentrations was observed during sexual maturation in chickens.
Both doses of cGnRH-I advanced the onset of egg-laying by few days, in
creased the initial eggs production, and significantly decreased T-4 a
nd T-3 plasma levels at 16, 18 and 20, and 16 and 20 week of age, resp
ectively. Results obtained demonstrate that cGnRH-I injected at 15 wee
k of chicken age nor. only advanced sexual maturation but also affecte
d concentration of blood thyroid hormones. It may be concluded that in
jections of cGnRH-I to immature chicken modify the activity of the hyp
othalamo-pituitary-thyroid axis.