59° 



Journal of Agruitltiire. [8 Oct., 1907. 



The Essential Qualities of Food. 



Each food must be suited to the species of animal and e\-en to the 

 individual. It must have the proper digestibility and palatableness and 

 have the amounts of ballast, etc., to which the species, through myriads 

 of generations, has been accustomed. I'he essential constituents enume- 

 rated above must be present and in the proper ratios to suit the animal's 

 needs. In most, if not all, of the domestic animals, variety in the food 

 leads to better results than if one ration be too exclusively relied on. 



If food be insufficient in quantity the animal has to draw on its 

 own fat and flesh which are actually digested in the body by the ferments 

 they contain, and sent into the blood-stream to make good the deficiency. 

 An animal when completely starved loses nearly all its fat, a great por- 

 tion of its muscle and spleen, a small portion of its heart substance, 

 but hardlv anv of its nervous matter. During violent exertion an animal 

 rarelv eats enough fuel food ; it draws on its supply of fat and glycogen 

 (the latter present in the liver and muscles) and makes good the loss in 

 these bodies during the rest which it ought to have after the exertion 

 is over. Underfeeding with any of the above-named essentials- will 

 injure the animal, the most common instance being underfeeding with 

 protein in the case of the ruminants. 



Overfeeding when it exceeds what the animal can retain as fat and 

 flesh, causes digestive disturbances. Excess of protein (an error Avhich 

 rarely occurs with ruminants) leads to- putrefactive changes in the bowel 

 by which poisonous products are produced and absorbed, causing muscular 

 weakness and loss of fat. 



Food Required for Growth. 



A voung animal requires protein, salts, and fuel food, in excess of 

 its repair and energy needs. The milk of each animal suits the needs 

 of the young of that species. Thus comparing cows' milk and human 

 milk, we find in cows' a larger amount of lime salts to suit the quick 

 bone-growth of the calf, whilst in human milk we find a larger amount 

 of lipoid to suit the quick brain-growth of the human infant. Protein 

 in excess of the repair amount is needed for the building of muscle and 

 gland ; fuel food for the formation of fat ; lime and phosphorus for bone; 

 lipoid for nerve, etc. 



Proteins and carbohvdrates can be transformed and laid on as fat 

 in a fattening animal. In a pregnant animal the -growth of the voung 

 in utero has to be considered. An animal with rapidlv growing wool 

 requires more protein. An animal recovering from fever or starvation 

 requires fuel food and protein in excess. 



Constituents of .Some Foods. 



To give here an extensive list of food-stuffs with their chemical content 

 would be impossible. To obtain such information special treatises on 

 the subject should be consulted. A few food-stuffs may however 

 be given as types ; the values, which are expressed in percentages, to be 

 taken as approximate only. 



It must be understood that a chemical analysis only gives the per- 

 centage amounts of each constituent in a particular food and gives 

 little or no indication how much of each can be actuallv absorbed bv 

 the animal. This is particularly the case with proteins and fibrous residue ; 

 a fraction of the latter being digested and a fraction of the former 



