138 Bulletin 154. 



the wastes of the animal machinery and build up new growth in 

 case of growing animals, or for the production of milk, wool, etc. 



Compounding of Rations. 



Nutritive ratio. — Since the protein on the one hand and the 

 carbohydrates and fat on the other, serve, in the main, different 

 purposes in the animal economy, it becomes evident that the 

 relative amounts of these nutritients in the food are important. 

 This relation is expressedas the " nutritive ratio," which means 

 the relation of digestible protein to digestible carbohydrates and 

 fat — the fat having been multiplied by 2)4^ before adding to the 

 carbohydrates, as explained above. The nutritive ratio is found 

 by dividing the carbohydrates, plus 2^ times the fat, by the pro- 

 tein. In the accompanying table. No. II, the sum of the carbo- 

 hydrates and fat, thus obtained, is given in the third column, 

 which divided by the protein as given in the second column gives 

 the second term of the nutritive ratio in the fifth column. 



A feeding stuff having a large proportion of carbohydrates and 

 fat as compared to protein is said to have a ' ' wide ' ' nutritive 

 ratio, while one having a small proportion of carbohydrates and 

 fat as compared to protein has a " narrow " ratio. While these 

 terms are relative, it may be said that a ratio greater than 1:6 is 

 wide, while one less than i :5 is narrow. The composition of feed- 

 ing stuffs, that is the proportion in which the different nutrients 

 occur, is determined by chemical analysis, but the amount of each 

 nutrient that is actually digestible has been determined by care- 

 ful experiments with living animals. Only the digestible nutri- 

 ents are considered in the tables given in this publication. 



Feeding Standards. — The amount of nutrients required and 

 the proportions in which each should be given, varies with the 

 kind of animal and the purpose for which it is kept : whether it 

 is growing, being fattened, doing work, or producing milk or 

 wool. Thus an ox at rest requires less food and the various 

 nutrients in different proportions than an ox at work ; a cow 

 producing milk requires more food and the nutrients differently 

 balanced than one not producing. 



Various investigators have condensed the results of many 

 experiments and much practical experience into what are called 



