FAT FORMATION FROM CARBOHYDRATES 153 



ents and the body fat is produced chiefly through cell activity from carbo- 

 hydrates and proteids. 



According to Rubner, 87 per cent of the digested fat in carnivora is 

 deposited in the tissues. In herbivora, in which more extensive bacterial 

 changes occur in the digestive tract, the amount is less (Kellner). For 

 oil emulsions it is 64.4 per cent, for the fats contained in roughages 

 47.4 per cent, for the fats in the grains and the seeds of the legumes 

 and their by-products 52.6 per cent. Kellner is of the opinion that the 

 last percentage would be applicable to the total fat content of the usual 

 feed mixtures. 



Under ordinar}^ conditions the main source of the body fat in our farm 

 animals is to be found in the carbohydrates. Fat formation from the 

 carbohydrates is not affected by the nutrient ratio, even within wide 

 limits (1:2.4 to 1:14). According to Kellner, 1 kg. of digested starch 

 can form 248 gm. (56.4 per cent of its total calories), crude fiber 253 

 gm. (57.0 per cent), cane sugar 188 gm. (46.2 per cent), body fat in 

 the mature ox. The rest is used up in the work of assimilation and in 

 the fermentation and decomposition processes of the stomach and intes- 

 tine. In this respect swine utilize the digestible carbohydrates, fats and 

 albuminous substances to the extent of 20 to 25 per cent more than 

 ruminants (no decomposition in the fore stomachs). 



The pentosans are hardly inferior to the carbohydrates as fat pro- 

 ducers. On the other hand, the organic acids take no part in fat forma- 

 tion. With reference to conditions obtaining in the secretion of milk, 

 see chapter on feeding dairy animals. 



While all three of the principal nutrients are concerned in the forma- 

 tion of fat, fcsh is formed by the proteids exclusively. 



A material increase of body protein (excepting nitrogenous products 

 in the form of milk, wool and fetal structures) does not take place in 

 mature animals. But such an increase is very great in suckling calves. 

 According to Soxhlet, the latter utilize on an average 72 per cent of the 

 digestible proteins in milk in the building of fleshy tissue. As age ad- 

 vances this percentage gradually decreases until it practically reaches 

 the zero mark in mature animals. In the latter the muscle fibers no 

 longer increase in number, and an increase in their size is possible in a 

 limited way only. Accordingly, this question does not concern us in 

 the fattening of mature animals in an average condition of flesh. In such 

 animals the chief end sought is fat production. 



Above everything else, the carbohydrates of the feed and the gly- 

 cogen stored up in the body tissues are the chief sources of muscular 

 energy. Proteins or albumen are required merely to the extent that 

 they are necessary for repairing the wasted muscle substance, which 

 is the same at rest as it is during or after exercise. The body fat is not 

 utilized in the production of muscular energy until the supply of carbo- 

 hydrates becomes insufifcient. The organized proteids are drawn upon 

 only in case both carbohydrates and fat fail to supply the demand. In 



