102 SCIENTIFIC FEEDING OF ANIMALS 



Another factor must also be considered, and it is 

 that green plants lose a certain amount of nitrogen- 

 free substance by respiration when dried in the air ; 

 at the same time there is a change of protein into 

 amides or similar substances whose nutritive value 

 is not that of protein (p. 65). It is very doubtful 

 then if the water of vegetation has any of the effect 

 ascribed to it. 



When drinking-water is taken into the body it 

 has to be raised to the temperature of the blood, 

 and that requires more or less heat according to 

 the temperature of the water. Under some condi- 

 tions food may have to be split up to supply the 

 heat necessary to warm the water, and so there is 

 less available for production. Well-fed animals, 

 ruminants for instance, generally produce more 

 heat than they require ; and in this case the intro- 

 duction of cold water, especially if given in small 

 quantities, as is done where the animal can help 

 itself, occasions no increased food metabolism. 

 Where animals are getting only a maintenance 

 ration, the consumption of cold water may cause 

 an increased use of nutrients for the production of 

 heat. Pigs, which quickly lose heat owing to 

 their thin covering of hair, may have to utilise some 

 of their food material for the production of heat, 

 if they are given a lot of cold, wet food. The 

 custom of giving pigs and cows a portion of the food 

 in warm drinks is quite sound, and drinking-water 



