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Concentrated Feeding-stuffs. [June, 



indispensable function in animal nutrition, may be neglected 

 in arranging diets for mature animals, as it is usually present 

 in sufficient quantity in all foods. This constituent of food 

 is of more importance in arranging diets for young, growing 

 animals. It is then especially important that the ration shall 

 supply suitable quantities of lime and phosphoric acid, since 

 these ingredients enter so largely into the composition of the 

 bones. The supply should be ample, but in the case of 

 phosphoric acid not very excessive. 



The mineral matter of foods should not include more than 

 a very small proportion of sand, as this is indicative of dirt. 

 It is impossible in practice to ensure that foods shall be 

 absolutely free from contamination of this character, but 

 there can rarely be any valid excuse for the presence of more 

 than, say, one or two per cent, of sand in a food. 



Digestibility of Foods. 

 It is usually not difficult to get an analysis of a food stating 

 the proportions of albuminoids, oils, and carbohydrates 

 present. Such an analysis, however, gives no information 

 as to the digestibility of each ingredient, and yet it is only 

 the digestible portions that can be regarded strictly as food. 

 Except in the case of albuminoids, this information cannot 

 be obtained in the laboratory, but recourse must be had to 

 actual trials with animals. For the purposes of the valuation 

 of foods, however, it will be sufficiently precise to take the 

 average digestibility as tabulated on p. 225. A table giving 

 the percentages of digestible constituents in average samples 

 of the commoner feeding-stuffs will be found in Leaflet No. 79, 

 p. 2. 



Productive Value of the Digestible Matter of Foods. 

 One further consideration requires to be taken into account 

 before a reliable estimate of the value of the food to the animal 

 can be secured. The materials digested by the animal from 

 a foodstuff cannot be applied solely and entirely to productive 

 purposes such as the production of milk, meat, or work. Even 

 the most easily digested foodstuff requires to be masticated 

 and forced along the alimentary tract, and in other ways 

 causes extra labour to the animal. The supply of the energy 

 required for this labour is a first charge upon the nutrients 



