The Short-Chain Fatty Acids of the Peripheral Blood of Goats

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Abstract
Considerable attention recently has been focused on the metabolism of short- chain fatty acids in ruminants. Volatile fatty acids now are known to be a major product of rumen bacterial fermentation (2, 4, 18). The acids thus pro- duced evidently are absorbed directly from the rumen into the blood stream. Reid (22) and MeClymont (15) have identified and measured acetic, butyric and propionic acids in the peripheral blood of sheep and cows. They reported as much as 10 mg. of volatile fatty acid per 100 ml. of blood; the majority of the acid was acetic. The blood of non-ruminants appears to contain less volatile acid (13, 17) ; Reid (21) found levels in dog blood as low as 1.4 rag. The possible significance of these short-chain acids in the blood of ruminants has been suggested by several reports. Isotopic acetate has been employed by Popjak et at. (3, 19) to demonstrate that the mammary gland utilizes acetate to synthesize longer chain fatty acids. Manometric study (5, 6) of mammary tissue slices has revealed that under certain conditions ruminant tissue utilizes acetate more actively than non-ruminant tissue. Tyznik and Allen (24) recently have observed that the low fat content of milk produced by cows on a low- roughage ration could be increased by supplemental feeding of acetate. The presence of these acids seems even more significant when one considers that the carbohydrate level of adult ruminant blood is somewhat lower than that of other mammals. However, the young ruminant is unusual in this respect, for at birth the glucose value may be as high as 115 rag. per 100 ml. of blood (1, 10). As the age of the animal increases, the blood glucose decreases until it reaches the adult range of 40 to 60 rag. per 100 ml. MeCandless and Dye (12) have considered this change in blood glucose to be concurrent with the develop- ment of the rumen. In this study the possibility that fatty acid levels in the blood may also reflect rumen development has been considered. The observations of lV(cCandless and Dye have been confirmed and extended.
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