Abstract
Genetic improvements in laying hens have increased egg productivity without increasing feed intake. Greater hen productivity may warrant increased amino acid needs. However, amino acid needs of commercial layers, beyond methionine and lysine, are poorly understood.This study was conducted to evaluate threonine responses on egg production traits in ISA-Babcock hens after peak production. Treatments consisted of five levels of digestible threonine (0.43, 0.47, 0.49, 0.52, and 0.57% of diet) administered at 62-72 or 70-80 wk of age. The lowest level of digestible threonine (0.43% of diet) represents 100% of the 1994 NRC recommendations and a threonine:lysine ratio of 0.62. Egg production, egg weight, feed intake, and feed conversion were measured during both time periods.Egg production (P<.011), egg weight (P<.012), and feed conversion (P<.004) improved as threonine was increased above the 1994 NRC suggested threonine recommendation. Increasing dietary threonine increased threonine intake (P<.001). A threonine:lysine ratio of 0.68 appears adequate for normal egg production traits of post-peak hens.
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