Chronic Heat Exposure Alters Protein Turnover of Three Different Skeletal Muscles in Finishing Broiler Chickens Fed 20 or 25% Protein Diets

Abstract

Heat-exposed chickens exhibit a lower growth rate and a depressed protein retention which may result from an alteration in protein metabolism. A high-protein diet seems to be beneficial under hot conditions because it tends to improve growth. Effects of high ambient temperature (32 vs. 22°C) and dietary crude protein (25 vs. 20%) on muscle protein turnover were investigated in finishing broiler chickens. At 5-6 wk of age, protein synthesis was measured in vivo in the Pectoralis major, Sartorius and Gastrocnemius muscles (flooding dose of [ 3 H]-phenylalanine). Protein breakdown was determined in the same muscles as the difference between protein synthesis and deposition. Chronic heat stress markedly reduced protein synthesis, irrespective of muscle type (P Ͻ 0.05). This was mainly related to the lower capacity for protein synthesis (muscle RNA/Protein) (P Ͻ 0.01). Chronic heat exposure also decreased protein breakdown in the P. major and Sartorius; this effect was not observed in the Gastrocnemius. Protein synthesis was more affected than breakdown, leading to reduced protein deposition, at least in the P. major and Gastrocnemius muscles. Increasing dietary protein content had no significant impact on muscle protein turnover. Particularly at 32°C, the high-protein diet did not significantly modify either protein synthesis, ribosomal capacity or translational efficiency. However, it favored muscle protein deposition, which was probably related to reduced proteolysis. In conclusion, we showed that chronic heat exposure decreased muscle protein deposition, mainly by reducing protein synthesis. Under these conditions, the impaired protein synthesis was not restored by a 5% higher protein intake. J.

Dietas de baixa proteína no desempenho de frangos criados em diferentes temperaturas

“…Cheng et al (1999) relataram que diminuir a proteína bruta da dieta pode melhorar o desempenho das aves criadas em ambiente quente. No entanto, Alleman & Leclercq (1997) e Temim et al (2000) demonstraram que esse procedimento acentuou os efeitos prejudiciais do estresse por calor sobre o desempenho dos frangos de corte.…”

The Effects of Different Amount of Protein and Vitamin e Supplementation in Rations on Lipid and Antioxidant Metabolism of Broilers Exposed to Heat Stress

“…Various nutritional strategies have been suggested to overcome the negative impact of heat stress in broilers. Especially recent researches have focused on dietary protein levels, and one other favorite way is adding antioxidants to the ration (Temim et al, 2000a;Temim et al, 2000b;Gonzalez-Esquerra & Leeson, 2006;Syafwan et al, 2011). Therefore, we have focused on; how antioxidants system affected from protein level and vitamin content, which has to be, organized to resolve or to minimize the negative effects of stress.…”

“…Temim et al (2000a) carried out a research that animals fed with diets containing 19% and 24% protein, at 22 o C and 32 o C. In this study, Temim et al (2000a) found that heat stress adversely affects the conversion metabolism of proteins to the muscles, and increasing protein percentage of the diet partially prevented this negative effect.…”

The Strategic Application of Electrolyte Balance to Minimize Heat Stress in Broilers

“…; Temim et al, 2000b;Faria Filho, 2003) These findings are associated with the different metabolism of each specific tissue: the breast present glycolytic metabolism, whereas the leg muscles present oxidative metabolism (Ain Baziz et al, 1996). The broilers exposed to heat stress on day 36 presented higher carcass fat content between 22 and 46 days of age compared with the broilers submitted to heat stress on day 25 and with those not exposed to heat stress.…”