J. Alan Murray 155 



for maintenance. Hence these differences. But, it may be asked, 

 is it seriously proposed that the starch equivalent for maintenance 

 should be reckoned by one formula and that for fattening by another? 

 If so, the starch equivalent system will scarcely survive the shock, 

 for it would be equally necessary to have another formula for milk 

 production and still another for work. Kellner's system is fundamentally 

 a mere convention. It does not establish a true "quantitative relation- 

 ship between the amount of food and the amount of fat, work or milk 

 it may be expected to produce." Its general applicability to these 

 problems rests essentially upon uniformity of the method, and if this 

 is undermined its more important advantages are destroyed. 



The factor 1-25 is presumably based on the relative amounts of 

 heat evolved from protein and starch when these substances are oxidised 

 in the animal's body, whereas the factor 0-94 is based upon the relative 

 amounts of fat formed from them. This point appears to have been 

 appreciated by Kellner and to have been allowed for by him as shown 

 below. 



It is generally agreed that the total thermic energy of the digestible 

 matter of the food is available for maintenance. It is, apparently, 

 for this reason that Wood and Yule make no correction for the "value"' 

 of the food. Such correction is, however, the very essence of Kellner's 

 system, and if it be not made the mimbers should not be called "starch 

 equivalents." The formula given by Wood and Yule is a reversion 

 to the system of Wolfi and his colleagues and predecessors. It differs 

 from what was formerly called "total digestible nutrients" only in 

 respect of the factor (1-25 instead of 1-0) applied to the protein; and 

 so far as the foods commonly used for maintenance rations are con- 

 cerned this difference is insignificant. The author suggests that if 

 such reversion is to be countenanced it would be well to revert to the 

 old-fashioned or some other name. Endless confusion must result if 

 the term "starch equivalent" be promiscuously applied to essentially 

 different things. 



This at once becomes evident when we turn to consideration of the 

 requirements of the animals. The specious similarity between Kellner's^ 

 estimate of 6 lb. and that of Wood and Yule of 6-35 lb. of starch 

 equivalent per day for maintenance of a 1000 lb. ox is deceptive. The 

 latter, according to the formula given, includes the whole of the thermic 

 energy of the digestible matter of the food; the former corresponds 

 to the dynamic portion only. In order to make this quite plain Kellner 



' The Scientific Feeding of Animals, p. 392. 



