Abstract
This experiment was conducted to evaluate the effects of in ovo injection of nano-selenium (Nano-Se) and nano-zinc oxide (Nano-ZnO) and high eggshell temperature (EST) during late incubation on blood parameters of broiler hatchlings. A total of 750 fertile eggs, were weighed and randomly distributed among 5 treatment groups on each of 5 replicate tray levels. The injection was performed on 17 d of incubation. Treatments included of: 1) Eggs not injected and incubated at normal EST (control); 2) Eggs not injected and incubated at high EST; 3) Eggs injected NaCl solution and incubated at high EST (sham); 4) Eggs injected NaCl solution containing 40 µg Nano-Se and incubated at high EST; 5) Eggs injected NaCl solution containing 500 µg Nano-ZnO and incubated at high EST. EST of 37.8ºC (normal) or 38.9ºC (high) was applied from d 19 to 21 of incubation. In ovo injection of Nano-Se and Nano-ZnO significantly increased activity of GSH-Px and SOD and total protein, but decreased the levels of corticosterone, cortisol, T4 and T3 at high EST. Injection of Nano-Se and Nano-ZnO had a significant role in alleviating the negative effects of high temperature incubation and heat stress by increased antioxidant activity and reduced oxidative stress.
Highlights
Temperature is a critical factor affecting embryonic development and growth
The objective of this study was to evaluate the effect of in ovo injection of Nano-Se and Nano-ZnO on antioxidant status, thyroid and glucocorticoid hormones, and some blood metabolites in broiler hatchlings exposed to high eggshell temperature (EST) during late incubation
The high EST during late embryogenesis significantly reduced the activity of GSH-Px (p = 0.003) and superoxide dismutase (SOD) (p = 0.006) compared to the control
Summary
Temperature is a critical factor affecting embryonic development and growth. Numerous studies have investigated the effects of different incubation temperatures on improving thermotolerance and its consequences (Al-Zhgoul et al, 2013; Morita et al, 2016; Piestun, Halevy, & Yahav, 2009). High incubation temperature results in changes in hormonal and metabolic regulations of chick embryos. Thyroid hormones and glucocorticoids are implicated in the acclimatory response to heat stress. Thyroid hormones play a major role in the embryonic growth as well as maturation of the organs during late incubation (Christensen et al, 2005). High temperature cause more stress during late incubation; with the onset of pulmonary respiration after internal pipping in the chick embryo, the presence of reactive oxygen species (ROS) and oxidative stress is higher (Moran Junior, 2007), while natural antioxidant reserves have not reached an adequate level for innate protection (Yigit, Panda, & Cherian, 2014). High temperature cause more stress during late incubation; with the onset of pulmonary respiration after internal pipping in the chick embryo, the presence of reactive oxygen species (ROS) and oxidative stress is higher (Moran Junior, 2007), while natural antioxidant reserves have not reached an adequate level for innate protection (Yigit, Panda, & Cherian, 2014). Sahin, Sahin, Kucuk, Hayirli, and Prasad (2009) reported that activity of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) is reduced in poultry under heat stress conditions, increasing the need for vitamins and minerals
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