Cyst(e)ine imbalance and its effect on methionine precursor utilization in chicks

Area of Science:

• Animal Nutrition
• Poultry Science
• Amino Acid Metabolism

Background:

• Methionine is an essential amino acid for poultry growth.
• DL-methionine (DL-M) and DL-hydroxy-methionine (OH-M) are common supplements.
• Dietary cystine can spare methionine, but excess may have adverse effects.

Purpose of the Study:

• To compare the bioefficacy of DL-M and OH-M in chick growth bioassays.
• To investigate the impact of varying cystine levels on methionine source utilization.
• To assess the effects of excess dietary cystine on feed intake and growth.

Main Methods:

• Five chick growth bioassays (9- or 12-d) using purified and corn-peanut meal diets.
• Diets were formulated to be deficient in methionine.
• Graded supplementation of DL-M and isosulfurous levels of OH-M were administered.
• Slope-ratio assays and multiple linear regression were used for bioefficacy estimation.

Main Results:

• OH-M showed a bioefficacy of 78.1% relative to DL-M when cystine was not limiting.
• In methionine and cystine-deficient diets, DL-M and OH-M showed similar efficacy.
• Excess dietary cystine (0.10%) depressed feed intake and growth, negatively impacting OH-M utilization.

Conclusions:

• The bioefficacy of OH-M relative to DL-M is influenced by dietary cystine levels.
• Excess cystine in methionine-deficient diets can be detrimental to chick performance and OH-M efficacy.
• Careful formulation considering both methionine and cystine is crucial for optimal poultry nutrition.