Changes in free amino acid concentrations in the blood, brain and muscle of heat-exposed chicks.

An experiment was conducted to analyse the changes in free amino acid concentrations in the blood, brain and muscle of chicks in response to 15 or 30 min exposure to high ambient temperature (HT). Food intake and body weight were not affected, while rectal temperature was significantly increased by short-term HT exposure. Several free amino acid concentrations increased in the blood, brain and muscle even with short-term HT, whereas levels of a few amino acids declined significantly. As well as the nonessential amino acids, essential amino acids also significantly increased with exposure to HT. 3-Methylhistidine, a marker of proteolysis, significantly declined in the muscle of HT chicks, implying a reduction of protein breakdown under HT. These results indicate that alteration of protein metabolism may occur in chicks even with short-term heat exposure.