Interactive effects of dietary amino acid density and environmental temperature on growth performance and expression of selected amino acid transporters, water channels, and stress-related transcripts.

Exposure to heat stress (HS) is one of the challenges facing the broiler industry worldwide. Various nutritional strategies have been suggested, such as altering dietary concentrations of some nutrients. Thus, we evaluated feeding different amino acid (AA) densities on live performance, Pectoralis (P.) muscles, and expression of selected AA transporters, water channels, and stress-related transcripts in a fast-growing broiler strain. Ross 308 chicks (n = 576) were randomly assigned to 4 dietary treatments (24 reps, 6 chicks per rep), differing in AA density (110, 100, 90, and 80% of a breeder's AA specifications). During 24 to 36 days of age, half of the birds were kept at a thermoneutral (TN) temperature of 20°C, whereas the other half were subjected to HS at 32° C for 8 h daily, making the treatment design a 4 × 2. The results revealed no interaction between housing temperature and AA density on growth performance or P. muscles weights. Feeding 80% AAs depressed BWG, FCR, and P. muscles at 36 d (P < 0.001). There was an interaction (P < 0.001) between AA density and temperature on the expression of all examined genes. Reducing the AA density beyond 100% upregulated the expression of AA transporter (CAT1, B0AT, b0,+AT, SNAT1, LAT1), HSP70, HSP90, glucocorticoid receptor (GR), and AQP3 in the TN birds' jejunum. Whereas in the HS birds, inconsistent expressions were observed in the jejunum, of which CAT1, B0AT, and LAT1 were markedly downregulated as AA density was reduced. In P. major of TN birds, reducing AA density resulted in upregulating the expression of all AA transporters, HSP70, GR, and AQP1, while downregulating HSP90 and AQP9. In contrast, AA reduction markedly downregulated CAT1, B0AT, and LAT1 in the P. major of HS birds. These findings indicate that the dietary AA level alters the expression of various genes involved in AA uptake, protein folding, and water transport. The magnitude of alteration is also dependent on the housing temperature. Furthermore, the results highlight the importance of adequate AA nutrition for fast-growing chickens under HS.

Effects of cerium oxide supplementation to laying hen diets on performance, egg quality, some antioxidant enzymes in serum and lipid oxidation in egg yolk.

This study was conducted to determine the effects of dietary cerium oxide levels (0, 100, 200, 300 or 400 mg/kg) on the laying performance, egg quality, some blood serum parameters and egg lipid peroxidation of laying hen. In total, one hundred and twenty 22-week-old brown Lohman LSL laying hens were randomly assigned to five groups equally (n = 24). Each treatment was replicated six times. Dietary supplementation of cerium oxide had no significant effect on feed intake and egg weight. The addition of cerium oxide to the laying hens' feed improved feed conversion ratio and increased (p < 0.05) egg production. Quality criteria of egg for except shell breaking strength were not affected by supplementing cerium oxide. In particular, supplementation of 200 and 300 mg/kg cerium oxide to the laying hens feed led to a significant (p < 0. 01) increase in egg shell breaking strength. Calcium and phosphorus concentration of serum increased significantly (p < 0.05) with supplementation of 100 mg/kg cerium oxide to laying hen diets. It was also observed that serum superoxide dismutase (SOD) activity and malondialdehyde (MDA) concentration decreased significantly with supplementation of cerium oxide in diets. Inclusion of cerium oxide resulted in a significant reduction in thiobarbituric acid reactive substance (TBARS) values in egg yolk in this study. It can be concluded that the addition of cerium oxide had positive effects on egg production, feed conversion ratio and egg shelf life. Based on the results of this study, it could be advised to supplement laying hens feed with cerium oxide as feed additives.