ENERGY METABOLISM AND THERMOREGULATION IN THE NEWBORN CALF; VARIATIONS DURING THE FIRST DAY OF LIFE AND DIFFERENCES BETWEEN BREEDS

Abstract

Rectal temperature (RT) and heat production (HP) of 10 Holstein–Friesian (HF), 10 Salers (S) and 7 Charolais (CH) calves held in a 10 °C environment were measured continuously during the first day of life. Rectal, skin and haircoat temperature, as well as haircoat weight, were determined in 31 other calves (11 HF, 11 S and 9 CH). Basal metabolism was measured in 18 other newborn calves (9 HF and 9 CH). Heat production decreased curvilinearly and reached a plateau 15 h after birth, when the haircoat was dry. Charolais and Salers calves could maintain their RT in spite of an HP 15 to 10% lower than that of HF calves. This difference could be explained neither by the lower physical activity of CH and S calves nor by better haircoat insulation. It seemed to result mainly from a lower metabolic rate of beef calves, according to the 13% lower basal metabolism of CH calves. These latter were also handicapped by slight acidosis, reduced physical activity, and delayed immunoglobulin absorption, which may contribute to their higher early postnatal mortality and morbidity. Key words: Calf, newborn, breed, energy metabolism, thermoregulation