The aim of this study was to investigate the effect of heat stress (HS) on digestibility of protein and fat and the expression of nutrient transporters in broilers. Forty-eight male Cobb500 chicks were used in this study. At day 14, birds were randomly divided into two groups and kept under either constant normal temperature (25 °C) or high temperature (35 °C) in individual cages. Five birds per treatment at 1 and 12 days post-treatment were euthanized, and Pectoralis major (P. major) and ileum were sampled for gene expression analysis. At day 33, ileal contents were collected and used for digestibility analysis. The total consumption and retention of protein and fat were significantly lower in the HS group compared to the control group. Meanwhile, the retention of crude protein per BWG was significantly higher in the HS group compared to the control group. In P. major and ileum tissues at day 1, transporters FATP1 and SGLT1 were down-regulated in the HS group. Meanwhile, FABP1 and PepT1 were down-regulated only in the ileum of the HS group. The converse was shown in P. major. The nutrient transporter FABP1 at day 12 post-HS was down-regulated in the P. major and ileum, but GLUT1 and PepT2 were down-regulated only in the ileum, and PepT1 was down-regulated only in the P. major compared with the control group. These changes in nutrient transporters suggest that high ambient temperature might change the ileum and P. major lipids, glucose, and oligopeptide transporters.
The present study was conducted to investigate the effect of heat stress (HS) on performance, digestibility, and molecular transporters of amino acids in broilers. Cobb 500 chicks were raised from hatch till 13 d in floor pens. At d 14, 48 birds were randomly and equally divided between a control group (25°C) and a HS treatment group (35°C). Birds in both treatment classes were individually caged and fed ad libitum on a diet containing 18.7% CP and 3,560 Kcal ME/Kg. Five birds per treatment at one and 12 d post treatment were euthanized and the Pectoralis major (P. major) and ileum were sampled for gene expression analysis. At d 33, ileal contents were collected and used for digestibility analysis. Broilers under HS had reduced growth and feed intake compared to controls. Although the apparent ileal digestibility (AID) was consistently higher for all amino acids in the HS group, it was not significant except for hydroxylysine. The amino acid consumption and retention were significantly lower in the HS group when compared to the control group. Meanwhile, the retention of amino acids per BWG was higher in the HS group when compared to the control group except for hydroxylysine and ornithine. The dynamics of amino acid transporters in the P. major and ileum was influenced by HS. In P. major and ileum tissues at d one, transporters SNAT1, SNAT2, SNAT7, TAT1, and b0,+AT, were down-regulated in the HS group. Meanwhile, LAT4 and B0AT were down-regulated only in the P. major in the treatment group. The amino acid transporters B0AT and SNAT7 at d 12 post HS were down-regulated in the P. major and ileum, but SNAT2 was down-regulated only in the ileum and TAT1 was down-regulated only in the P. major compared with the control group. These changes in amino acid transporters may explain the reduced growth in meat type chickens under heat stress.
Heat stress is one of the most challenging environmental stresses affecting domestic animal production, particularly commercial poultry, subsequently causing severe yearly economic losses. Heat stress, a major source of oxidative stress, stimulates mitochondrial oxidative stress and cell dysfunction, leading to cell damage and apoptosis. Cell survival under stress conditions needs urgent response mechanisms and the consequent effective reinitiation of cell functions following stress mitigation. Exposure of cells to heat-stress conditions induces molecules that are ready for mediating cell death and survival signals, and for supporting the cell’s tolerance and/or recovery from damage. Heat-shock proteins (HSPs) confer cell protection against heat stress via different mechanisms, including developing thermotolerance, modulating apoptotic and antiapoptotic signaling pathways, and regulating cellular redox conditions. These functions mainly depend on the capacity of HSPs to work as molecular chaperones and to inhibit the aggregation of non-native and misfolded proteins. This review sheds light on the key factors in heat-shock responses for protection against cell damage induced by heat stress in chicken.
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