الفهرس 
Effect of heat stress on productive performanceOnly 14 pages are availabe for public view
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Abstract
The aim of this study was to overcome the deleterious effects of heat stress on productive and reproductive performance of growing and laying Japanese quail by using some dietary additives, such as organic chromium; organic zinc and mannan oligosaccharides (MOS) alone or with other feed additives. All quail chicks were fed ad libitum on a basal growing diet during the first week of age. After that, a number of 750 quail chicks were assigned randomly and equally to ten dietary treatment groups. After 8 weeks of age, 25 birds -#102;-#114;-#111;-#109; each group were taken randomly and continued on their treatments to study the effects of treatments on egg production and egg quality. The first group was received a basal diet without any supplement and saved as control group. The second and third groups were fed the basal diets supplied by organic chromium (600 mg or 1200 mg of chromium yeast), the forth and fifth groups were fed the basal diets supplied by organic zinc (20 mg or 40 mg of Bio-plex zinc), the sixth group was fed the basal diet supplemented with 1 g/kg of MOS. The other groups (-#102;-#114;-#111;-#109; seventh to tenth) were similar to groups -#102;-#114;-#111;-#109; second to fifth, but MOS was added to these diets by 1 g/kg. br Data were collected to determine the effect of different treatments on productive and reproductive performance, blood constituents and humoral immune response against SRBCs. br The results showed that live body weight, body weight gain and feed consumption were improved as response to adding the low level of organic chromium or the prebiotic (MOS) or their combination. Feed conversion was numerically improved in all treatment groups. Egg production and hatchability percentages were significantly improved especially in laying quails that fed Zn-supplemented diets, a similar trend was also obtained for chromium and MOS diets and their combination. Egg weight, egg mass and exterior and interior egg quality traits were insignificantly influenced by different treatments. Humoral immune response of growing quails against SRBCs challenge was significantly improved in quails that fed Zn or MOS supplemented diets or their combinations. Plasma total proteins, albumin and globulin of growing quails were significantly influenced by different treatments, but in laying period, plasma total protein did not significantly affected. Plasma total lipids and plasma cholesterol levels of growing quails were significantly decreased for Cr or MOS diets or their combination. Liver enzymes activity (AST, ALT) and thyroid hormone (T3) levels were significantly increased by dietary treatments, especially with zinc and chromium. br It could be concluded -#102;-#114;-#111;-#109; the present study that, dietary supplementation with chromium yeast (600 mg or 1200 mg/kg diet), low level (20 mg/kg diet) of organic zinc, MOS with a level of 1 g/kg diet or a combination of these additives may be used as alternatives to pharmacological growth promoters, for enhancing productive and reproductive performance of growing and laying quails.