In order to investigate the fasting metabolism of goats, the present experiment was carried out using a castrated male and two tracheostomized female Japanese Saanen goats, weighing 26-35 kg. The total length of fast was consecutive seven days, and feces and urine were daily collected for the determination of nitrogen excretion. On the 5th, 6th and 7th days of fasting, expired gas was collected for oxygen and carbon dioxide analysis. In two goats, the jugular blood was sampled for measurement of plasma total amino acid concentration on the final day of fasting. From the data of oxygen consumption and nitrogen excretion in the urine, the amount of body protein decomposed and heat production were calculated. The following results are obtained.
1. The body weight rapidly decreased during the first few days of fasting, and then the decrease became slow and the rate of decrease in body weight seemed to be almost constant. The degree of decrease in body weight was almost parallel to the excretion of feces and body materials.
2. The fecal nitrogen excretion was 0.4-0.8 g per day on the 7th day of fasting, and this amount might be considered to be metabolic fecal nitrogen.
3. In calculating the heat production of goats, LUSK's and BENEDICT's methods coincided comparatively well in results The difference in yalue between these inethods waslto2per cent.
4. The heat production from protein decomposition was 12.6-20.4% of the total heat production on the 5th to 7th day of fasting.
5. The heat production per 50kg body weight of a goat was 1036.67Cal. per day in fasting conditin when it was calculated based on the body surface area. When it was calculated based on the metabolic body size, the heat production was 1090.09Cal. per day per 50kg body weight of a goat.
6. The concentration of plasma total amino acid was 121.2 and 145.4μm/100 ml, and the ratio of essential to non-essential plasma amino acid concentrations was 0.85 and 0.72 in goats B and C, respectively, on the 7th day of fasting.