254 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



hydrates and fats to considerable extent, but their peculiar work must 

 all be done by themselves. Such is the concurrent testimony of a vast 

 amount of experimenting. 



Again, of the whole ration consumed only a portion is digested and 

 used to supply the animal's wants ; the rest is voided as excrement, and 

 valuable only for manure. It is important, then, that as much should 

 be digested as i^ossible. The value of the food will depend upon the 

 amount the animal digests from it. 



Economy in feeding requires, then, that the greatest amount of food 

 be digested, and that this digested material contain sufficient albumi- 

 noids. 



An excessive proportion of albuminoids is, however, uneconomical. 

 The albuminoids are the costliest i)arts of the foods. No more should 

 be used than necessary. 



Proper proportions of digestible albuminoids, carbohydrates, and fats 

 in the food are the chief requisites of economical feeding. 



Digestion of foods hy animals, as tested hy Uuropean experiments. 



316. The digestibility of different foods and food mixtures by dif- 

 erent animals under varying circumstances has been tested by a very 

 large number of experiments in the German experiment stations. The 

 method consists in feeding animals with rations of known amount and 

 composition, carefully collecting, weighing, and analyzing the excre- 

 ments, the undigested portion, and subtracting the latter from the 

 former. The following examples will serve for illustration : 



In the stables of the station at Weende, under the direction of Pro- 

 fessor Henneberg, two full-grown oxen were fed during one period of 

 about two weeks with oat straw, during another period with bean straw, 

 a third with clover hay, a fourth with meadow hay, and so on. Duiing 

 some of these periods a small amount of bean meal was added. The 

 ration was at all times such as to keep the animals in fair and uniform 

 condition. Careful weighings and analyses were made of fodder and 

 excrement, that is to say, of the total and the undigested material, and 

 from these the digestibility of the food was calculated. For instance, 

 in one of the experiments of this series the ox consumed daily 1G.9 

 iwunds of meadow hay, or what is called here "English grasses." 



