Factors affecting broiler processing parameters and plasma corticosterone.

Abstract

Two experiments were conducted to determine the influence of broiler strain, sex, and age on resting plasma corticosterone levels and the latter's relationship to various broiler production and processing parameters. In Experiment 1, strain and sex differences in 58-day farm weight (FWT), dressed carcass weight (DC), yield (Y), abdominal fat (AF), abdominal fat expressed as a percentage of DC (PAF), and plasma corticosterone (C) measures were assessed in five commercial broiler strains fed a lower [3086 kcal metabolizable energy (ME)/kg] versus higher (3306 kcal ME/kg) energy ration. The higher energy diet was formulated and used to produce excess abdominal fat. In Experiment 2, the effect of broiler age (4, 6, and 8 weeks) on resting plasma C was determined. Results of Experiment 1 indicated that although strain significantly influenced AF, and although feeding the higher energy diet significantly elevated FWT, DC, Y, AF, and PAF, strain and dietary energy effects on plasma C were nil. However, a significant strain X dietary energy interaction on plasma C levels was observed. Likewise, although female broilers had greater PAF measures than male birds, sex did not influence resting plasma C values. Plasma C was not correlated to AF measures. Experiment 2 results showed plasma C at 6 (3.3 ng/ml) and 8 weeks (2.9 ng/ml) was significantly depressed from the 4-week (4.9 ng/ml) sampling. Thus, future studies involving adrenal functioning in broilers should take into consideration the influence bird age might have on interpretation of results.