Plasma corticosterone concentrations in growing chickens fed diets formulated to promote different rates of growth

Seasonal temperature and its influence on plasma corticosterone, triiodothyronine, thyroxine, plasma protein and packed cell volume in mature male chickens

1. The relationship between seasonal changes in environmental temperature and hematological parameters was investigated in mature, single comb white leghorn (SCWL) male chickens. 2. Samples of blood plasma, obtained monthly from two groups of birds over two separate 12 month periods, were analysed for corticosterone (CT), 3,5,3'-triiodothyronine (T3), thyroxine (T4), plasma protein (PP), and packed cell volume (PCV). 3. Statistical analyses revealed that blood plasma concentrations of T3 were significantly correlated negatively with monthly dry-bulb temperatures. 4. There were no consistent or significant relationships between monthly dry-bulb temperature and CT, T4, PP or PCV over the two 12 month periods. 5. The results of this study indicate that blood plasma concentrations of T3 are influenced by season of year in mature, male domestic fowl.