766 TRANSACTIONS OF SECTION M. 
of digestible protein, ceases to have any direct influence on increase in live- 
weight. 
We may fairly conclude, then, that about two pounds of protein per 
1,000 pounds live-weight per day is sufficient for a fattening ox. This amount 
is repeatedly exceeded in most of the districts where beef production is a 
staple industry, the idea being te produce farmyard manure rich in nitrogen. 
The economy of this method of augmenting the fertility of the land is very 
doubtful. The question is one of those for the solution of which a combina- 
tion of accurate experiment and modern accountancy is required. Protein 
is the most expensive constituent of an animal’s dietary. If the scientific 
investigator, from a study of the quantitative composition of the proteins of 
the common farm foods, and the economist, from careful dissection of farm 
accounts, can fix an authoritative standard for the amounts of protein required 
per 1,000 pounds live-weight per day for various types of animals, a great step 
will have been made towards making mutton and beef production profitable 
apart from corn-growing. 
For many years it has been recognised that an animal requires not only 
so much protein per day, but a certain quota of energy, and many attempts 
have been made to express this fact in intelligibie terms. Most of them 
have taken as basis the expression of the value of all the constituents of the 
diet in terms of starch, the sum of all the values being called the starch 
equivalent. This term is used by various writers in so many different senses 
that confusion has often arisen, and this has militated against its general 
acceptance. Perhaps the most usual sense in which the term is used is that 
in which it means the sum of the digestible protein multiplied by a factor 
(usually 1.94) plus the digestible fat multiplied by a factor (usually 2.3), 
plus the digestible carbohydrates. This, however, gives misleading values 
which are too high in concentrated foods and too low in bulky foods, the 
discrepancy being due to the larger proportion of the energy of the bulky 
foods which is used up in the much greater work of digestion which they 
require. Kellner and his school have devised a method which measures the 
starch equivalent by experiment, a much more satisfactory and practical 
method than any system which depends purely on calculation. 
An animal or a number of animals are kept on a maintenance diet so that 
their weight remains constant. To this diet is added a known weight of 
starch, and the increase in weight observed. The animal or animals are then 
placed again on the same maintenance diet for some time, and then a known 
weight of the food to be tested is added, and the increase in weight again 
observed. The data thus obtained indicate that so many pounds of starch 
produce as much increase in live-weight as so many pounds of the food under 
experiment, from which it is easy to calculate how many pounds of starch 
are actually required to produce as much increase in live-weight as 100 pounds 
of the food under experiment. The starch equivalent thus found expresses 
an experimentally determined fact which is of immediate practical value in 
arranging a dietary, its value, however, depending on the accuracy with 
which it has been determined. Kellner and his colleagues have thus deter- 
mined the starch equivalents of all the commonly used foods. Their values 
for concentrated foods, and other foods commonly used in Germany, have been 
determined with considerable accuracy, and with the method which has also 
been devised for defining the relation between the experimentally determined 
equivalent and the equivalent calculated from the analysis by means of a 
formula, they form by far the most reliable basis for arranging a feeding 
ration including such kinds of foods. 
But roots, which form the staple of the diet of fattening animals in Great 
Britain, are not used on the same scale in Germany, and Kellner’s starch 
equivalents for roots have not been determined with sufficient accuracy or 
under suitable conditions to warrant their use for arranging diets under our 
conditions. 
This, and the fact that the term starch equivalent is so widely misunderstood, 
is no doubt the reason why the Kellner equivalent has not been more generally 
accepted in Great Britain. An advance will be made in the practice of feeding 
as soon as the starch equivalent of roots has been accurately determined under 
our conditions, when the Kellner equivalents will no doubt come into general use. 
