Production Traits of Leghorn Pullets in Controlled Temperatures

Production traits, including sexual maturity, egg production, egg weight, shell strength, body weight, and feeding efficiency were studied with four strains of Leghorn pullets exposed to temperatures of 10°, 23°, and 36°C. The effect of abruptly changing these temperatures at 4-week intervals and of diurnally cyclic temperatures was investigated in avian bioclimatic chambers. The experiments started when birds were 20 weeks of age, and continued for 24 weeks. Abrupt changes to a temperature of 36°C. resulted in mortality, and susceptibility to heat-stroke increased with age. Egg production was highest in the low temperature for the control groups of birds, whereas feed efficiency tended to be best in the high or cyclic temperature groups. With the petite strain, egg production and feed efficiency were best in the medium temperature. Shifting the birds at intervals of 4 weeks tended to lower the overall egg production. When pullets were shifted from 22° to 34°C. they consistently lost weight, which was regained when the birds were shifted from 34° to 10°C. Egg weight and shell thickness was greatest in the low-temperature group. The percentage of blood spots was very high in two of the strains tested, and tended to be reduced at high temperature. Length of the toe nails varied directly with ambient temperature.