Metabolic changes in thoroughbred and pony foals during the first 24 h post partum

Metabolic rates, rectal temperatures and respiratory quotients (RQ) were determined during the first 24 h post partum in Thoroughbred and pony foals and in relation to environmental temperature. Both breeds had high metabolic rates (greater than 200 W/m2) during the first hour post partum when they were wet and shivering; by 4 to 24 h values were fairly steady at about 153 and 105 W/m2 for Thoroughbred and pony foals, respectively. At birth, rectal temperature was lower in Thoroughbred foals than in pony foals; values increased during the first hour, and then decreased. At 24 h of age, both breeds had a rectal temperature of 38.4 degrees C. RQ values were high (greater than 0.9) at birth in both breeds, declining to about 0.82 by 4 to 24 h of age. At similar environmental temperatures, the metabolic rates per unit area of Thoroughbred foals were higher than those of pony foals at all ages. The results indicate that breed differences may exist between the thermal responses of newborn Thoroughbred and pony foals.