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Nitrogen metabolism in genetically fat and lean chickens
P A Geraert1, M G MacLeod, M Larbier
1Station de Recherches Avicoles, Institut National de la Recherche Agronmique, Monnaie, France.
Poultry Science
|November 1, 1990
Summary
Genetically lean chickens (LL) exhibit superior protein retention efficiency compared to fat chickens (FL), regardless of dietary protein levels. This difference is linked to reduced amino acid degradation in LL birds, impacting growth and fattening rates.
Area of Science:
- Animal Science
- Poultry Nutrition
- Genetics
Background:
- Genetically fat (FL) and lean (LL) chicken lines exhibit distinct growth and body composition traits.
- Understanding nutrient utilization differences is crucial for optimizing poultry production.
Purpose of the Study:
- To investigate the impact of dietary protein content and early growth rate on growth, nitrogen retention, energy metabolism, and amino acid catabolism in FL and LL chickens.
- To identify genetic and nutritional factors influencing energy partitioning and protein efficiency.
Main Methods:
- Two experiments varying dietary protein levels (131–251 g/kg) and assessing growth parameters from 4 to 7 weeks of age.
- Measurement of nitrogen retention, energy metabolism (metabolizability, basal metabolic rate, diet-induced thermogenesis), and amino acid catabolism (uric acid excretion).
Main Results:
- No significant differences in energy utilization (metabolizability or expenditure) were found between FL and LL lines.
- LL chickens demonstrated higher protein retention efficiency than FL chickens.
- FL chickens exhibited increased dietary amino acid degradation, indicated by higher uric acid excretion, correlating with lower protein retention efficiency.
Conclusions:
- Energy utilization is similar between FL and LL chickens; differences lie in energy partitioning towards lipid vs. protein deposition.
- Lean chickens (LL) are more efficient at retaining protein, likely due to reduced amino acid degradation.
- Selection for growth rate influences fattening rates and nitrogen metabolism, with fast-growing birds being fatter and showing greater metabolic differences.