CONTRIBUTION OF COLOSTRAL FAT TO THERMOGENESIS AND GLUCOSE-HOMEOSTASIS IN THE NEWBORN PIG

This study was designed to determine the effects of colostral fat on energy metabolism, fat oxidation and glucose homeostasis in newborn pigs maintained during the first 29h of life at thermal neutrality (34-degrees-C) or in the cold (21-degrees-C). Piglets were intragastric fed normal colostrum (NFC,6% fat) or colostrum deprived of fat (LFC,<1% fat). A total of 21 meals of 15 to 18g colostrum/kg birthweight was given at 65- to 70-min intervals. Feeding NFC resulted in a higher amount of retained fat with the highest value being obtained in the 34-degrees-C group (P<0.01). Fat oxidation represented 47% of the absorbed fat in NFC-fed piglets at 34-degrees-C; it was 4.5 fold higher in piglets fed NFC than in those fed LFC (P<0.01), and 1.8 fold higher at 21-degrees-C than at 34-degrees-C (P<0.01). At both temperatures, feeding LFC resulted in a lower energy balance (P<0.01), whereas nitrogen balance was not affected by temperature and colostrum treatments. At 29 hours of age, rectal temperature was the lowest in piglets fed LFC at 21-degrees-C (P<0.05). Postnatal enhancement of fat metabolism in relation to environmental and nutritional conditions was evidenced at the tissue level through an adaptation of lipoprotein lipase and cytochrome oxidase activities, especially in the red rhomboideus muscle and the liver. Liver glycogen mobilization rate was higher at 21-degrees than at 34-degrees-C (130 vs 107 mg/h, P<0.01), and for LFC-fed piglets than for those fed NFC (135 vs 103 mg/h, P<0.01). Muscle glycogen concentration was only dependent on temperature. At 29 h of age, NFC-fed piglets maintained normal blood glucose concentrations at both temperatures, whereas despite a lower plasma insulin/glucagon molar ratio (P<0.05) appropriate for gluconeogenesis, those fed LFC exhibited lower values (P<0.05) approaching the hypoglycaemic threshold at 21-degrees-C. At 29 h of age plasma glucagon was higher at 21-degrees-C (P<0.01). The results obtained at the animal and tissue levels indicate the efficiency of colostral fat for fat oxidation and suggest the close relationship between fat utilization and glucose homeostasis during the first 29 h of life.