Energy metabolism of groups of broiler breeders in open‐circuit respiration chambers

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Abstract
1. Energy metabolism of broiler breeders housed in groups was measured in large open‐circuit respiration chambers. 2. The design, function and calibration of the chambers are described. Each of the three chambers has a capacity for 24 pullets or adult layers, or 16 adult broiler breeders. Control of ventilation rate is by calibrated choked‐flow nozzles. 3. Before experiments were started the system was assessed by CO2 infusion and recovery and ethanol combustion studies. Percentage CO2 recoveries were greater than 98 of infused and the mean (± SD) quotient of CO2 produced to O2 consumed from the combusion of ethanol was 0–67 (±0.02). 4. Forty‐eight broiler breeder hens in lay were placed in the respiration chambers (16 per chamber) and fed at different rates from around maintenance to about twice this value. 5. The energy required for maintenance (MEm)was 365 kJ/kg W 0.75 d and the efficiency of utilisation of metabolisable energy (ME) for production (kp ) was 0.70. Starvation heat production was about 350 kJ/kg W0.75 d and was shown to affect the derived values of the energetic parameters when included in the relationship between retained energy and metabolisable energy intake. Published results were recalculated and found to support this.

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