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 short term exposure of eggs to magnetic field before incubation on hatchability and post-hatch performance of meat chickens.

The effects of exposing meat-type breeder eggs to magnetic field (MF) before incubation on hatchability traits (percents of hatchability and hatchability failures of eggs), chick weight at hatch, and post-hatch performance (weight gain, feed intake, and feed conversion ratio (FCR)) from 1 to 39 d of age were investigated. Eggs from a Ross flock at 38 weeks of age were exposed to MF of 18 Gauss (1.8 mT) at 50 Hz for 0, 15, 30, 45, 60, and 75 min (MF0, MF15, MF30, MF45, MF60, and MF75) before incubation. Exposing eggs to MF did not influence hatchability of eggs and chick weight at hatch. However, chickens of MF60 and MF75 treatments had lower weight gain and feed intake than those of the non-exposed treatment at 39 d of age. MF exposure of eggs did not influence FCR of chickens between 1 and 21 d of age, but tended to increase FCR, albeit non-significantly, between 22 and 39 d of age. It is concluded that exposing meat-type breeder eggs to MF of 18 Gauss (1.8 mT) at 50 Hz for up to 75 min did not influence hatchability traits and chick weight at hatch. However, MF exposure of eggs for 60 and 75 min reduced body weight gain and feed intake of chickens over the 39-d experimental period.