Development of thermoregulation in the kitten

In normal kittens thermoregulation developed over the first 45 days of age. This maturational sequence went from a mean rectal temperature (T_B) of 37.0°C at 5 days of age to adult levels (38.2 ± 0.2°C) at about 7 weeks of age. Up until about 14 days of age the predominant response to being removed from the nesting box and placed at an ambient temperature of 23 to 25°C was a decrease in T_B of about 0.02°C/min. In response to stronger thermal challenges (i.e., short periods at + 60°C or ? 15°C) all kittens showed, from the first day of life, the ability to detect and move along a thermal gradient as reflected in an approach to warmth and an avoidance of cool. At ?15°C the kittens showed a decrease in T_B of about 0.2°C/min at 10 days decreasing to about 0.1°C/min at 40 days of age. After 45 days of age shivering as well as piloerection appeared immediately with cold onset and for short periods (i.e. less than 2 hours) at this temperature combined behavioral and physiological regulation sufficed to maintain the temperature at approximately 37.5°C. In response to heating the kittens showed a mean T_B increase of about +0.05°C/min at 10 days decreasing to +0.02°C/min at 45 days of age, at which time panting was also fully developed. These data demonstrate that the development of normal thermoregulation in the cat follows a time course of up to seven weeks.