INFLUENCE OF PROPOETION OF WATER 165 



powers of digestion are unequal. Thus the same 

 meadow hay supplied by Wolff to sheep and horses 

 had for the former an albuminoid ratio of 1 : 9'1, and 

 for the latter a ratio of 1 : 6*7. The horse, as we have 

 Been, digests the nitrogenous constituents of hay nearly 

 as well as the sheep, but fails in digesting some of the 

 non-nitrogenous constituents. Hay is thus a more 

 nitrogenous food for horses than for sheep. 



The advantage of employing a fixed albuminoid ratio 

 in any diet is less than has been generally supposed, 

 the same effect being often produced by diets varying 

 within pretty wide limits. The proportion of albu- 

 minoids most suitable for various diets will come under 

 consideration in the next chapter. 



(4) Influence of Proportion of Water. — The nutri- 

 tive value of a food to the animal is affected by 

 the quantity of water with which it is associated. All 

 the water in the food or drink has to be raised to the 

 temperature of the animal body, while a part is 

 exhaled as vapour in the breath and perspiration, and 

 in this process of vaporisation a very considerable 

 further amount of heat is consumed. Kellner found 

 that for 100 of water consumed by oxen in a stable as 

 food and drink, 46'3 appeared as an average in the 

 faeces, 29'2 in the urine, while 24*5 was vaporised. 

 The quantity of water required by an animal depends 

 partly on the kind of food supplied; fibrous foods, as 

 straw and hay, require considerably more water than 

 corn. The oxen in the stable consumed about 4 of 

 water to 1 of dry matter when fed on straw and hay, 

 and only 3 to 1 when starchy and oily foods were given. 

 Foods rich in albuminoids increase the demand for 

 water, as more urea has to be removed from the system. 



