The main objective of this study was to elucidate the effect of short- term exposure of Japanese quail eggs to acute high incubation temperature on embryonic development and on the ability of post- hatched chicks to cope with subsequent heat stress conditions during the growing period. A total of 998 Japanese quail eggs were divided into two groups, the first group (470 eggs) was maintained at the recommended incubation temperature (37.5 ˚C), while the second group (528 eggs) was exposed to 39.5 ˚C for two hours at days 3, 7 and 13 of embryogenesis. After hatching, chicks from each incubation temperature were randomly assigned to four dietary treatments, a control, a high-energy (+150 kcal ME/kg diet more than the recommended level); a high-lysine (10% more than in the control diet) and a vitamin C supplemented diet. During the experimental period all of the quail were fed ad libitum and they received similar hygienic and managerial conditions. The rearing temperature was 32±2 ˚C during the entire experimental period. Pre-hatching exposure of eggs to 39.5 ˚C did not significantly affect the post-hatching body weight and weight gain during the growing period. While, vitamin C or high-energy diet increased it. Body temperature, respiration rate (RR) and the relative weights of the thymus, spleen and bursa of Fabricius were not significantly affected by the pre-hatching temperature or the post-hatching dietary treatments. However, the high-energy and vitamin C diets caused obvious decreases in RR at 4 weeks of age. Pre-hatching heat treatments caused a slight increase in the plasma triiodothyronine (T3) and plasma thyroxine (T4) concentrations, however, was significantly decreased by both the pre- hatching temperature and post- hatching dietary treatments at 6 weeks of age. Based on the above results, it was concluded that pre-hatching exposure of quail eggs to high temperature and post-hatching feeding of a high-energy or vitamin C supplemented diet can be recommended for alleviating the deleterious effects of heat stress during the growing period. Manuscript profile

An experiment was conducted to investigate the effect of thyroid gland activity modulation (Hyper or hypothyroidism) on energy utilization in broiler chickens. Two hundred and forty one-day-old Cobb broiler chicks were distributed into three dietary metabolizable energy (ME) treatment groups (80 chicks each). The control group (E0) was fed basal diet (3150 kcal/kg diet), the second group (E1) was fed low ME diet (3000, kcal/kg diet) with different thyroidal treatments and the third group (E2) was fed very low ME diet (2850 kcal/kg diet) with thyroidal treatments. Thyroidal treatments were applied at the beginning of the 2nd week, where (T0) was a control treatment; two hyperthyroidism groups induced by administration of Eltroxin (T1) or calcium iodide (T2), and hypothyroidism group induced by carbimazole administration (T3). Results showed that plasma thyroidal hormones (T3, T4) concentrations and their ratio T3 / T4 showed considerable changes related to thyroidal treatments. Plasma glucagon (G) level was significantly increased while insulin (I) level and I / G ratio were significantly decreased as affected by lowenergy diets. Carbimazole administration group had the lowest plasma insulin level and I / G ratio compared to other treatments. Moreover, calcium iodide significantly increased adenosine triphosphate (ATP), Total adenylate(TA) and phosphatepotential(PP) while carbimazole significantly decreased adenosine diphosphate (ADP) and adenosine monophosphate (AMP). Histological examination of thyroid gland sections reflect the beneficial use of calcium iodide (CaI) as a safe additive without hazards effect on thyroid gland histology. Results suggested that calcium iodide could be used to maximize the utilization of lowenergy diets, via its modulating action of thyroid gland activity. Manuscript profile