Effects of free and dipeptide forms of methionine supplementation on oxidative metabolism of broilers under high temperature.

Our previous studies have shown that methionine supplementation could help to attenuate the effects of heat stress on the metabolism of broiler chickens. Here we investigated for the first time the effects of methionine supplementation in the form of DL-methionyl-DL-methionine on broilers subjected to heat stress during the growth phase. Broilers were divided into two groups; one group was reared under thermoneutral conditions and the other under continuous heat stress (30 ±â€¯1 °C, 60% relative humidity). Both groups were subdivided into three dietary treatments: a methionine-deficient (MD) diet, a diet supplemented with free methionine (DL-M), and a diet supplemented with methionine dipeptide (DL-MM). Broilers raised under chronic heat stress had lower feed intake and weight gain than broilers raised under thermoneutral conditions (P < 0.05). There were no differences in animal performance between methionine-supplemented diets (DL-M and DL-MM). Heat-stressed birds had significantly higher heterophil/lymphocyte (H/L) ratio than thermoneutral birds. Under heat stress, broilers fed DL-M and DL-MM diets had lower H/L ratio than birds fed the MD diet. Higher concentrations of carbonylated proteins and lower concentration of reduced glutathione were observed in broilers raised under heat stress. In comparing heat-stressed broilers, we found that birds fed the DL-M diet had lower concentrations of thiobarbituric acid-reactive substances and carbonylated proteins than those fed the MD diet (P < 0.05). Higher expression of glutathione peroxidase (GPX) and glutathione synthetase (GSS) genes was observed in heat-stressed broilers (P < 0.05). Under heat stress, the MD diet increased GPX expression compared with other diets. Under thermoneutral conditions, the DL-M diet resulted in the highest GSS expression. There was a negative correlation between DNA methylation and GPX and GSS expression. Our results showed that supplementation of broiler diets with free methionine or methionine dipeptide may help attenuate the effects of heat stress through enhanced activation of genes related to the glutathione antioxidant system. Methionine effects were found for gene regulation, gene expression, and post-translational processing.

Lippia gracilis Schauer essential oil as a growth promoter for Japanese quail.

The use of antibiotics as performance enhancers in animal feeding is declining, so Lippia gracilis Schauer essential oil (LGSEO) could be used as a potential substitute for the conventionally used growth promoters. The LGSEO contains components such as carvacrol and thymol, which kill and/or control pathogenic bacteria, increase population of beneficial organisms, act against oxidative processes and onto nutrient digestibility and absorption. The aim of this study was to investigate the action and the effects of LGSEO as a growth promoter in the diet of Japanese quail by examining their productive performance, intestinal microbiology, blood biochemical parameters, hepatic thiobarbituric acid reactive substances (TBARS) content and intestinal gene expression. A total of 252 two-day-old quail (Coturnix coturnix japonica) were assigned to 3 treatments in 7 replicates, using 12 birds per experimental unit. The treatments consisted of a basal diet, basal diet + LGSEO at 400 mg/kg of diet and basal diet + chemical antimicrobial (bacitracin methylene disalicylate) at 500 mg/kg of diet. The experimental period was 34 days. The highest feed intake (P < 0.01) was found in the group receiving the conventional antimicrobial, whereas the best feed conversion (P < 0.01) was shown by the animals receiving LGSEO. Escherichia coli growth was restricted in the quail receiving the growth promoters. Salmonella spp. growth was controlled by the treatment containing the conventional antimicrobial. There was no difference between the treatments (P > 0.05) for the concentration of aspartate aminotransferase and alanine aminotransferase enzymes in the blood or hepatic TBARS content. Birds receiving negative-control treatment exhibited a higher expression of sodium-glucose cotransporter (SGLT1), while those receiving the treatment with essential oil showed lower catalase (CAT) and glutathione peroxidase (GPX7) expressions compared to the conventional antimicrobial and control groups, respectively. Lippia gracilis Schauer essential oil is a powerful performance enhancer for Japanese quail by virtue of its abilities to improve their intestinal environment, balance the microbial population and reduce energy expenditure for oxidative processes.