PRINCIPLES THAT GOVERN FEEDING 187 



slightly increase the quantity of milk by protecting some 

 of the nitrogenous substance of the food from oxidation 

 and increasing the amount available for the formation of 

 cells in the milk glands. 



7. The nutritive ratio for the food of milch cows is 

 comparatively narrow. The explanation is first, that pro- 

 tein is necessary for the production of dry substance in the 

 milk; and second, that within certain limits the percentage 

 of the dry substance will be increased with an increase of 

 the nitrogenous substance in the food. 



8. Sheep require relatively more fodder than larger an- 

 imals and fodder with a relatively narrower nutritive ratio, 

 both for maintenance at rest and in fattening. They can 

 bear a more concentrated food than cattle and the food 

 should be less watery. For the production of wool only, it 

 is only necessary to keep the animals in good condition, 

 hence an excess of nitrogenous food would be waste when 

 wool is the sole or even principal object sought. 



9. Swine eat much more food relatively than other an- 

 imals, especially during the early stages of growth and fat- 

 tening, and they increase in weight correspondingly. But 

 in both respects their ability to increase in relative weight 

 diminishes with advancing age and with advancement in the 

 fattening period. 



10. Horses that work severely call for not only a pro- 

 portionate increase in the amount of the food, but they also 

 require food with a greater proportion of nitrogenous 

 constituents. 



Notwithstanding the valuable assistance which these 

 tables render to the feeder in choosing and balancing ra- 

 tions suitable to the needs of the animals fed, the fact re- 

 mains, that rations balanced from the standpoint of chem- 

 ical analysis are only to be considered as approximate rather 

 than as absolute guides. The following influences among 

 others may lead to variations in the results from feeding 

 rations so balanced : ( I ) The inherent and cultivated appe- 

 tites of animals to take the same food vary greatly and 



