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Why are young broiler chickens fatter than layer-strain chicks?
H D Griffin1, D Windsor, C Goddard
1Department of Cellular and Molecular Biology, AFRC Institute of Animal Physiology and Genetics Research, Roslin, Midlothian, U.K.
Summary
Broiler chicks deposit more abdominal fat than layer chicks due to higher very low-density lipoprotein uptake and minimal triglyceride turnover in their adipose tissue. This impacts overall fat deposition rates in poultry.
Area of Science:
- Poultry nutrition and metabolism
- Lipid metabolism in avian species
- Comparative physiology of fat deposition
Background:
- Broiler chickens are selectively bred for rapid growth and meat yield, often leading to increased fat deposition.
- Layer chickens are bred for egg production, with different metabolic priorities compared to broilers.
- Understanding the mechanisms of fat deposition is crucial for optimizing poultry production and health.
Purpose of the Study:
- To compare the incorporation of very low-density lipoproteins (VLDL) into abdominal fat pads of broiler and layer chicks.
- To investigate the turnover rate of adipose tissue triglycerides in both broiler and layer chicks.
- To elucidate the physiological differences contributing to varying fat deposition rates in these two types of poultry.
Main Methods:
- Intravenous injection of 14C-labelled very low-density lipoproteins (VLDL) into 5-week-old broiler and layer chicks.
- Quantification of VLDL incorporation into abdominal fat pads.
- Measurement of [14C]palmitate turnover in adipose tissue using half-life (t1/2) determination.
- Assessment of adipose tissue triglyceride turnover rates.
Main Results:
- Abdominal fat pads of broiler and layer chicks incorporated 6.0% and 3.9% of injected 14C-VLDL, respectively.
- VLDL flux accounted for approximately 65-70% of fat deposition in broilers, significantly higher than in layers.
- [14C]Palmitate in layer chick adipose tissue had a half-life of 2-3 days, indicating active turnover.
- No significant turnover of adipose tissue triglycerides was observed in broiler chicks.
Conclusions:
- Higher VLDL incorporation and minimal triglyceride turnover in broiler adipose tissue contribute significantly to their greater fatness.
- The rapid turnover of triglycerides in layer chicks suggests a metabolic adaptation for energy utilization rather than storage.
- These findings highlight key differences in lipid metabolism that influence fat deposition in broiler versus layer chickens.