Abstract
This study was conducted to determine the effect of hot environment and dietary crude protein level (CP) on performance, carcass characteristics, meat visual quality, muscle chemical composition and malondialdehyde (MDA) concentration of tissues in broilers. Two hundred and sixteen 21-d old Arbor Acre broilers were used in a 4×3 factorial arrangement and randomly reared in 4 environmental chambers and fed on 3 diets with different CP levels for 3 weeks. The results showed: (1) when air temperature (AT) rose to 33°C, average daily feed intake, average daily gain, carcass weight, right breast meat weight, left thigh and drumstick meat weight decreased (p<0.05) and feed conversion rate decreased (p<0.05), but the ratio of carcass to live weight and of left thigh and drumstick meat weight to carcass weight increased (p<0.05). (2) There were significant differences in pH and shear force in breast meat, and shear force, L* and a* in thigh meat (p<0.01 or 0.05) among hot environments. Dietary CP level tended to affect breast meat pH and pH and L* of thigh meat (p<0.06 or 0.09). Compared to the normal temperature (22°C), low temperature (15°C) and hot humid (AT 33°C, relative humidity (RH) 80%) treatments significantly (p<0.05) decreased the tenderness of thigh meat. L* and a* value in thigh meat under high temperature treatments, regardless of RH, were higher (p<0.05) than those under normal temperature. (3) Protein content in breast and thigh meat of broilers fed under high temperature (33°C) was lower (p<0.05) than that under 22°C, but fat content had an adverse change. High temperature (33°C) increased the moisture of breast meat significantly (p<0.05). Protein content in breast meat increased significantly (p<0.05), in which fat content had an adverse change (p<0.05), when the dietary protein rose. (4) MDA concentration in liver and breast meat under hot humid (AT 33°C, RH 80%) treatment increased markedly (p<0.05). (5) High humidity could sharpen the bad effect of high temperature on performance, carcass yield and choice cuts, crude protein and moisture content in breast meat. It was concluded that a hot environment could affect the performance and meat quality of broiler chicks more significantly
Highlights
High environmental temperature is one of major concerns for broiler producers in many countries of the world, especially in the hot and humid tropics
Dietary protein had no significant effect on average daily feed intake (ADFI), average daily gain (ADG) and feed conversion ratio (FCR) (p>0.05) except that increasing crude protein level (CP) level had a trend to depress FCR during the first week of the trial (p = 0.06)
In accordance with the previous reports, the result of the present study indicated that the growth performance was decreased by heat exposure
Summary
High environmental temperature is one of major concerns for broiler producers in many countries of the world, especially in the hot and humid tropics. Many studies have been conducted to investigate the effect of thermal environment and dietary nutrient level on the growth performance of broilers. Since the broiler have no sweat glands and are fully covered with feathers, the thermoregulations are challenged under hot weather. The reduced feed intake, body weight gain and feed conversion.
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