Does excess dietary protein improve growth performance and carcass characteristics in heat-exposed chickens?

The effects of two environmental temperatures (22 and 32 C, constant) and five dietary protein contents (10 to 33% CP) were investigated in 4- to 6-wk-old broiler chickens. High ambient temperature reduced growth rate, feed efficiency, and breast muscle proportion and increased abdominal fat proportion. Irrespective of ambient temperature, increasing dietary protein content improved growth performance and carcass characteristics. At 32 C, there was a greater heterogeneity of the data, and bird responses were lower than at 22 C. We concluded that under conditions of chronic heat exposure, diets containing the highest protein levels, 28% and 33% compared with 20% CP, slightly improved chick performance. However, the effect was low and, in our experimental conditions, modifying dietary protein supply (variations in the total quantity of protein) is not sufficient to help broilers to withstand hot conditions.