i9i i.] Starch Equivalents of Feeding Stuffs. 725 



body and its organs, respiration, &c, are continually using 

 up energy, which is stored in the body as some component 

 part of it. To repair this waste, food must be given, and if 

 a sufficient quantity is fed to counterbalance the losses 

 exactly, then the animal is said to be on a maintenance diet, 

 and its body weight would neither increase nor decrease. 

 Any food given beyond maintenance requirements is used 

 for production purposes, the three chief ways of which are 

 manifested either in the formation of body tissue (fat) or 

 milk, or in the performance of mechanical work. A diet 

 which contains more nutrient material than the animal 

 requires for maintenance purposes is a production diet. We 

 are indebted to Continental investigators, and particularly 

 to Kellner, for our knowledge of the fact that the value of 

 the digested nutrients depends upon the food in which they 

 are contained. Experimental evidence has been amply 

 furnished in support of this view, and the conclusions are 

 now generally accepted. 



Much of the difference in the availability of the various 

 feeding stuffs is directly connected with the amount of crude 

 fibre which they contain, for it is well known that this mate- 

 rial is difficult of mastication and digestion in the state in 

 which it is found in old grass, hay, straw, husks of cereal 

 grains, &c. When the crude fibre is freed from the hard 

 incrusting materials which accompany it in the case of coarse 

 fodders, it has been found to have a high feeding value; in 

 fact, it is then equivalent to starch. It is the difficulty of 

 making the fibre fit for assimilation which withdraws so much 

 energy from the body as to make that which comes from the 

 food of little total gain ; in other words, the net increase of 

 energy in the body is slight. An illustration of this point 

 would be furnished by comparing the animal body, regarded 

 as a store of energy, with a reservoir of water into which 

 water was being pumped from another and lower source, 

 say a stream, by means of a ram pump. If the water 

 used by the pump in forcing the supply to the reservoir 

 were large in proportion to that which entered the reservoir 

 owing to the resistance which the pump had to overcome, 

 then the case could be compared with a feeding stuff of low 

 availability. When, on the contrary, much of the water of 



