Threonine Requirement in Female Broilers Affected by Age and Dietary Amino Acid Levels.

Abstract

The reported threonine requirement for the maximum performance of broilers ranges widely. To clarify the reasons of these wide ranges, two experiments were conducted using female Arbor Acres strain broilers. In Experiment 1, to elucidate the effect of age on the threonine requirement, six feeds containing graded concentrations of dietary threonine from 0.70 to 0.90% were supplied to the broilers at four growing stages from 5 to 15, 15 to 25, 25 to 35 and 35 to 45 days of age. In Experiment 2, to confirm the effect of age and amino acid levels on the threonine requirement, the feeds containing two levels of amino acids, 90 and 100% of the NRC requirement, with six graded concentrations of threonine were supplied to the broilers at 8 to 18 and 28 to 35 days of age. At the end of each experiment, the body weight gain and feed consumption were recorded. The dietary threonine requirement expressed as a percentage of diet and crude protein level for the maximum body weight gain and feed efficiency decreased with age and had a tendency to increase with increasing dietary amino acid levels. The amount of threonine per kg body weight gain increased with age, but the effect by increasing dietary amino acid levels was not clear.