Abstract
1. Metabolic rate was determined once a week in pullets from commercial flocks of the local White Leghorn strain from the age of 1 d to 13 weeks.
2. The equations relating minimal resting metabolic rate and body weight were: for body weights of 40 to 163 g Y ‐ 1–83 W 0.986, and for 163 to 1 200 g Y = 11.64 W 0.623, where Y = O2 consumption (ml/bird h) and W = body weight (g).
3. The relationship between lower critical temperature (Td) and age may be described by two equations: for pullets of 1 to 21 d of age Y = 35 ‐ 0.286 X, and for 21 to 70 d of age Y = 63.3 X‐ 0.254, where Y = T d(°C) and X = age (d).
4. Td related to body weight is also described by two equations: for body weights of 40 to 163 g Y = ’42 ‐ 1.18 W0.480 , and for 163 to 800 g r = 42 ‐ 3.60 W0.260
5. These equations could be used to calculate the Td on a day‐to‐day basis related to age or body weight.