Effects of selenium supplementation on the oxidative state of acute heat stress‐exposed quails

This study aimed to evaluate the effect of heat stress (HS) and selenium supplementation on markers of stress, meat quality and gene expression. For this, meat quails of 42 days of age were fed a diet that either met [0.33 mg/kg, nutritional demand for selenium (SS)] or did not meet [0.11 mg/kg, selenium deficient (SD)] the nutritional demands for selenium during the 7 days of evaluation. In addition, the animals were kept at either a thermal comfort temperature (25 °C) or exposed to HS (38 °C for 24 h). Glutathione synthetase (GSS), glutathione reductase (GSR) and uncoupling protein (UCP) gene expression were influenced by the interaction between temperature and diet. Animals subjected to HS and fed the SS diet exhibited the highest GSS and GSR gene expression. In terms of UCP gene expression, the lowest values were observed in HS animals on the SD diet. Glutathione peroxidase 7 (GPX7) gene expression, body temperature (BT) and creatine kinase (CK) activity were influenced by both selenium supplementation and HS. Aspartate aminotransferase (AST), alanine aminotransferase (ALT) activity and creatinine content all were influenced by the diet/environment interaction. The highest AST activity, ALT activity and creatinine levels were observed in animals that were both on the SD diet and exposed to HS. HS animals also exhibited an increased heterophil/lymphocyte ratio and lower triiodothyronine (T3) hormone levels than birds that remained at the comfortable temperature. Animals subjected to HS and fed with selenium supplemented diet showed better results regarding gene expression and, thus, better results for the activities of enzymes used as stress markers, which could be due to the higher antioxidant capacity provided by the action of the studied genes.     

Comparison of growth curve parameters of organs and body components in meat- (Coturnix coturnix coturnix) and laying-type (Coturnix coturnix japonica) quail show interactions between gender and genotype

1. The objective of this study was to estimate growth parameters of carcass components (wing, thighs and drumsticks, back and breast) and organs (heart, liver, gizzard and gut) in males and females of one meat-type quail strain (Coturnix coturnix coturnix) and two laying strains (Coturnix coturnix japonica) designated either yellow or red.

2. A total of 1350 quail from 1 to 42 d old were distributed in a completely randomised design, with 5 replicates of each strain. The carcass component weights and body organs were analysed weekly and evaluated using the Gompertz function; growth rates were evaluated through derivative equations.

3. The meat-type strain presented the highest growth rates in carcass components and organs. Across strains, females showed the highest weight of internal organs at maturity compared to males.

4. Females had greater growth potential in breast, wings and back than males for both yellow and red laying quail.

     

Levels of supplementation of inorganic selenium and vitamin E for meat quail aged 0 to 14 and 14 to 35 days

Two experiments were carried out to determine the levels of supplementation of inorganic selenium (Se) and vitamin E (VE ) in diets of quails aged 0–14 and 14–35 days old. A completely randomized design was used in a factorial design (Se = 0.1125; 0.2250; 0.3375 and 0.4500 mg kg^?1 diet^?1 × VE  = 10; 23; 36 and 49 IU  kg^?1 diet^?1). In experiment 1, quail (n  = 2,400) were aged 0–14 days and were divided into 16 treatments, with three replicates of 50 birds. In experiment 2, quail (n  = 1,680) were aged 14–35 days and were divided into the same treatments, with three replicates of 35 birds. At age 0–14 days, the levels of VE did not affect performance (p  > .05); however, the feed conversion (FC ) was influenced by a quadratic effect (p  = .0515), according to the level of Se, with a higher level estimated at 0.29 mg Se kg^?1 diet^?1. At age 14–35 days, there was a linear effect with interaction (Se × VE ), for FC (p  = .0150) and weight gain (WG ; p  = .0266). FC (Se, p  = .0048 and VE , p  = .0019) and WG (Se, p  = .0049 and VE , p  = .0068) improved linearly with increasing levels of Se and VE . The feed intake (FI ) decreased linearly (p  = .0582) as a function of VE . The carcass yield showed a quadratic effect (p  = .0056) on the levels of VE , with a higher yield estimation of 27.24 IU VE /kg of diet. It can be concluded that the optimum level of supplementation at age 0–14 days was 0.29 mg Se kg^?1 diet^?1 and 10 IU VE  kg^?1 diet^?1 and at age 14–35 days, it was 0.4500 mg Se kg^?1 diet^?1 and 49 IU of VE  kg^?1 diet^?1.     

Models for predicting protein requirements for meat quail

Three experiments were carried out to determine the crude protein requirements for maintenance (CPm) and weight gain (CPg) of meat quail and to develop protein‐requirement prediction models. Experiment 1 was conducted to determine CPm by the nitrogen‐balance technique. The regression of nitrogen balance on nitrogen intake revealed a CPm requirement of 2.94 g/kg^0.75/day. Experiment 2 was aimed at determining CPm by the comparative‐slaughter technique. Retained nitrogen (RN) and nitrogen intake (NI) were quantified considering the metabolic weight of the birds. The linear regression of RN on NI provided a CPm estimate of 6.63 g/kg^0.75/day. Experiment 3 was conducted to determine CPg. The regression of body nitrogen from the carcasses on fasted body weight revealed CPg estimates of 407.68 (0–7 days), 501.76 (8–14 days), 470.40 (0–14 days), 517.44 (15–21 days), 627.20 (22–28 days), 423.36 (29–35 days), and 517.44 mg/g (15–35 days). The protein‐requirement prediction models developed for meat quail aged 0–7, 8–14, 0–14, 15–21, 22–28, 29–35, and 15–35 days were CP = 2.94.W^0.75 + 0.408.G; CP = 2.94.W^0.75 + 0.502.G; CP = 2.94.W^0.75 + 0.470.G; CP = 2.94.W^0.75 + 0,517.G; CP = 2.94.W^0.75 + 0.627.G; CP = 2.94.W^0.75 + 0.423.G; CP = 2.94.W^0.75 + 0.517.G, respectively, where: W^0.75 =  metabolic weight (kg), and G =  daily weight gain (g).