Effects of temperature treatments on the energy and nitrogen metabolism of fed chickens

1. Calorimetric measurements were made for 5 d on individual broiler chickens (1 kg) fed ad libitum and acclimated or unacclimated to six temperatures from 2 to 35 °C (constant), or alternated between these temperatures and 22 °G (alternated). For the four treatments, heat production was related to temperatures and the resultant curves were significantly different.

2. Food intake, heat production and maintenance energy requirement all increased linearly with decreasing temperature. Metabolisability of the diet was only 13.8 kJ/g at 35 °C, compared with a mean value for all treatments of 14.1 kJ/g.

3. Energy retention and nitrogen (N) retention (g/d, or % dietary N) were maximal at 22 and 16 °C, however the amount of energy deposited as protein remained relatively constant below 30 °C.

4. Net availability of metabolisable energy was calculated in two ways: by calculating the increase in heat production of fed birds above their starvation values giving a mean value of 0.82; this was similar to the mean regression coefficient which included starvation data, and related ME intake and energy retention; but without these data availabilities ranged from 0.45 at 35 °C to 1.0 in the cold.

5. Acclimation or alternating of temperature had very few significant effects, however there were temperature x acclimation effects on N retention and heat production. Similarly alternating temperature significantly increased food intake and heat production at high temperatures, but decreased metabolisability of the diet to 13.7 kJ/g at 35 °C from an overall mean of 14.1 kJ/g.