The heatincrement in fasting sheep of acetic acid partially neutralized with sodium hydroxide.

In previous work Armstrong & Blaxter (1957) found that when acetic acid was given to fasting sheep as the sole source of energy it was inefficiently utilized in the sparing of body tissues from oxidation. Five experiments gave a mean heat increment of 40.9 kcal/Ioo kcal of acid metabolized, a value which greatly exceeded the heat increments found when propionic or n-butyric acids were given. A noticeable feature of the experiments with acetic acid was the marked acidosis that developed when the acid was administered, and it was suggested that the high increments of heat might be associated with accumulation of acid. Respiration-chamber experiments by Mollgaard & Thorbek (1941) with milking cows given A.I.V. silage were cited in this regard, for they showed that severe acidosis due to mineral acid increased the heat increment and that neutralization of the acid reduced it. This paper describes three experiments in which fasting sheep were given acetic acid partially neutralized with sodium hydroxide in an attempt to prevent acidosis ; the results are compared with those previously reported when acetic-acid solutions were given. A brief account of some of the findings has been published (Armstrong, Blaxter & Graham, 1958).