186 SWINE 



wurzels, turnips, etc. Adding meal to such a ration im- 

 proves it still further. Feeds like these which contain 

 from 85 to 90 per cent of water, carry with them more 

 water than the ordinary pig can use to the best advan- 

 tage. If these are cooked, and part of this water driven 

 out, the ration will be more nearly balanced. 



CHANGES IN RATIONS. 



Effect on Coefficient of Digestibility. — Some of the 

 most recent experimental data show that a pig is very 

 subject to changes in his ration. The last digestion and 

 metabolism experiment conducted by the writer seems to 

 show that a pig, when fed a certain ration for a consider- 

 able length of time, will digest this more thoroughly after 

 a few weeks than at first. That is, the coefficient of di- 

 gestibility gradually rises; consequently if the pig is to 

 produce the best results from a given ration, he must be 

 fed this for a long enough time to become used to it. 



Effect on Protein Metabolism. — Aside from the effect 

 on digestibility, as previously noted, when the factor of 

 waste is once established it has a tendency to continue 

 at that rate indefinitely, and is very difficult to eliminate 

 or even to reduce. In order to change from a ration that 

 is high in protein to one that is low in protein, four weeks' 

 time should be consumed. If the time during which such 

 a change is made is too short, the pig, on account of the 

 tenacity with which the factor of waste is maintained, 

 will metabolize and excrete more than is received in its 

 ration. This will result in a breaking down of the protein 

 tissue of the body, and in loss of vitality; possibly also 

 in loss in live weight. At any rate the pig will make 

 smaller gains under such conditions. 



In the case of breeding animals the loss of vitality un- 



