COMPARISON OF FOODS. 113 



3. Influence of proportion of Water. The feeding 

 value of roots, and of other foods rich in water, is often 

 diminished by the fact that a part of the heat they pro- 

 duce in the body is consumed in raising the water they 

 s apply to the temperature of the animal, and of vaporis- 

 ing a part of it as perspiration. With sheep the normal 

 proportion of water to dry food is about 2:1; with 

 horses 2 3 : 1 ; with cattle about 4:1. An excess of 

 water produces a waste of food. 



A sheep feeding on turnips in winter in the open field, 

 consuming, say, 20 Ibs. of roots per day, will receive in 

 its food about 1 8 Ibs. of water, of which 14 Ibs. is beyond 

 that necessary for nutrition. This 14 Ibs. of water has 

 to be raised from near the freezing point to the tempera- 

 ture of the animal body, a rise of at least 60 Fahr. To 

 warm the water to this extent will require the combus- 

 tion of about 51 grams of carbo-hydrates, (reckoned as 

 starch,) equal to about 8 per cent, of the total food con- 

 sumed. The actual waste of food will however greatly 

 exceed this, as a part of the extra water will be exhaled 

 as vapour in the breath and perspiration, and to vaporise 

 1 Ib. of water at the temperature of the animal body 

 requires the combustion of 64 grams of starch. 



The consumption of an excess of water will also some- 

 what increase the amount of albuminoids oxidised in the 

 animal body, and thus occasion a waste of the nitrogenous 

 part of the food. 



The economy of supplying sheep on roots or green 

 fodder with dry food in addition, is obvious from the facts 

 just stated ; by so doing the quantity of water consumed 

 by the animal is diminished, and its proportion in the diet 

 brought more nearly to a normal ratio. 



