endocrine response of hybrid rabbits of different ages and under two environmental temperature conditions

The trial was carried out on 44 hybrid male rabbits in order to study the plasma levels of testosterone (T), dihydrotestosterone (DHT), cortisol (C), triiodothyronine (T3) and thyroxine (T4) in relation to age (71 vs 85 days) and environmental temperature (20 vs 27°C). Age didnotaffect T, DHT, T + DHT. Only T/DHT resulted lower (P <0.01) for older rabbits. The 71 and 85 day-old rabbits showed similar levels of C, T3, T4 and T4/T3. The different thermal levels did not influence T, DHT, T + DHT, T/DHT and C. The rabbits reared at 27°C showed similar values of T3 and T4 but a higher (P <0.05) T4IT3 ratio in comparison with those kept at 20°C. Digestible energy intake/metabolic weight appeared to influence (P <0.01) T3 positively and T4/T3 negatively.