Image Number 8 for United States Patent #6449896. A method of
determining the weight of animals and the development of plants
in a controlled environment. The method includes measuring the
increase in CO.sub.2 production over a test period. CO.sub.2
production is a measure of the metabolic rate and this is
related to weight of animals and development of crops which can
often be determined by weight. There is illustrated a poultry
rearing house having vents, lights and an air heater. CO.sub.2
sensors are connected to a CO.sub.2 controller and in turn to a
central controller. To test the increase in CO.sub.2 production
over time, the birds are settled into a passive state with no
feed and the lights turned off. The level of CO.sub.2 produced
is measured. The vents are closed. After a time, the rate of
Co.sub.2 produced is measured and the increase calculated.