Heat shock proteins as a key defense mechanism in poultry production under heat stress conditions

Over the past years, the poultry industry has been assigned to greater production performance but has become highly sensitive to environmental changes. The average world temperature has recently risen and is predicted to continue rising. In open-sided houses, poultry species confront high outside temperatures, which cause heat stress (HS) problems. Cellular responses are vital in poultry, as they may lead to identifying confirmed HS biomarkers. Heat shock proteins (HSP) are highly preserved protein families that play a significant role in cell function and cytoprotection against various stressors, including HS. The optimal response in which the cell survives the HS elevates HSP levels that prevent cellular proteins from damage caused by HS. The HSP have chaperonic action to ensure that stress-denatured proteins are folded, unfolded, and refolded. The HSP70 and HSP90 are the primary HSP in poultry with a defensive function during HS. HSP70 was the optimal biological marker for assessing HS among the HSP studied. The current review attempts to ascertain the value of HSP as a heat stress defense mechanism in poultry.

125 Supplementing extra dietary DL-methionine mitigates effects of higher stocking density on growth performance, meat quality, and health status of broiler chicks

This study was to determine if 30% extra supplemental DL-methionine could improve growth performance, meat quality, and health status of broilers stocked at a high density. A total of 560 day-old male Cornish cockerel chicks were divided into 4 treatment groups: 2 stocking densities (2.9 and 3.8 kg/ft2) and 2 supplementations of DL-methionine (grower: 2.90 or 3.77 g/kg and finisher: 2.60 or 3.38 g/kg). Chicks were fed the same corn-soybean meal-based starter diet and then experimental diets (grower: 6.4 g SAA/kg, finisher: 5.9 g SAA/kg, n = 10 pens/treatment). Growth performance and mortality were recorded, and blood and tissue samples (3 chicks/pen) were collected at the end of each period. Data were analyzed by two-way ANOVA. High stocking density decreased (P < 0.05) BW and (or) ADG of growers and finishers. Both high stocking density and methionine decreased (P < 0.05) ADFI and the high methionine improved (P < 0.05) feed use efficiency of chicks during the grower-finisher period. Neither treatment affected feather coverage, mortality, incidences of diseases, or dressing percentage. The high methionine improved (P < 0.05) meat to bone ratio of thigh, and exerted mixed effects (P < 0.05) on texture of breast and thigh. Dietary methionine and stocking density showed no major effects on tissue lipid profiles, but moderate effects (P < 0.05) on plasma concentrations of total cholesterol and(or) triglycerides of chicks. Fatty acid profiles in the liver and breast of chicks were unaffected by either treatment. The two treatments enhanced (P < 0.05) tibial maximum breaking strength (15–20%) and plasma alkaline phosphatase activity of growers. In conclusion, the high stocking density affected growth performance, meat quality, and health status of broilers. Supplementing 30% extra dietary methionine seemed to mitigate some of those effects. (Supported in part by Evonik Nutrition & Care GmbH, Germany)

128 Additional dietary DL-methionine affects tissue redox and inflammation status of broiler chicks in response to high stocking density

We determined if 30% extra supplemental DL-methionine affected oxidative and inflammatory responses of broilers stocked at a high density. A total of 560 day-old male Cornish cockerel chicks were divided into 4 groups: 2 stocking densities (2.9 and 3.8 kg/ft2) and 2 methionine supplementations (grower: 2.90 or 3.77 g/kg and finisher: 2.60 or 3.38 g/kg). Chicks were fed the same corn-soy starter diet and then respective experimental diets (grower: 6.4 g SAA/kg, finisher: 5.9 g SAA/kg, n = 10 pens/treatment). Blood and tissues (3 chicks/pen) were sampled at the end of each period. Data were analyzed by two-way ANOVA. The high density elevated (P < 0.05) glutathione concentration in the plasma, breast, and thigh of growers, but decreased (P < 0.05) it in the liver of growers and thigh of finishers. The high methionine elevated (P < 0.05) glutathione concentration in the thigh at both ages. There were interactions (P < 0.05) between dietary methionine and stocking density on activities of antioxidant enzymes including GST in 2 or more tissues at both ages and GPX and SOD in the thigh of growers. Hepatic expression of inflammation-related gene IL-6 was decreased (P < 0.05) by the high density, while heat shock protein genes HSP70 and HSP90 were decreased (P < 0.05) by the high methionine. Expression of stress-related genes TNFα and JNK was decreased (P < 0.05) by a combined high methionine and density treatment. The high methionine decreased (P < 0.05) finisher thigh and breast malondialdehyde concentrations and grower plasma glucose concentrations. Neither the density nor the methionine supplementation affected concentrations of plasma ferric reducing ability, serum amyloid A, and corticosterone or hepatic protein carbonyl. In conclusion, the high stocking density showed bilateral effects on the redox and inflammatory responses of broilers. Supplemental extra methionine modulated some of those effects.