THE FARMER'S MAGAZINE. 



25 



So far from being easily understood, the Nutrition 

 of Animals is, perhaps, the most complicated 

 department which exists in agricultural science; 

 one in which inquirers as to " the why and where- 

 fore" are, as yet, only gropmg their way ; requiring 

 to be much further investigated before practice and 

 science can be considered as fully united. A suf- 

 ficient amount of research, however, has been made 

 into this subject to enable us to understand the 

 rationale of our business, and, in some degree, to 

 prevent that waste which must arise from the indis- 

 criminate use of those substances which we employ 

 as the food of animals, without reference to their 

 fitness for the purpose which we intend them to 

 serve, and also the nature of those agencies which 

 exert an influence, whether favourable or the re- 

 verse, on the full development of the nutritive powers 

 of those substances. 



In building up the structure of an an'mal, it is 

 necessary to bear in mind that the elements of 

 which the food is composed are of two different 

 classes ; first, those containing nitrogen, which 

 enters into the composition of bones, hair, horn, 

 wool, skin, blood, and muscle or flesh; ani, secondly, 

 those in which nitrogen does not exist, and which 

 are destined to support respiration and animal heat, 

 and also to produce fat. 



All the elements which produce the flesh and fat 

 of animals are found to be gathered together in 

 their food, and ready to be converted to their several 

 uses without undergoing any material change. In 

 vegetable bodies we have vegetable albumen, glu- 

 ten, and casein, which are identical with flesh, the 

 curd of milk, and the blood. The phosphates, 

 common salt, &c., which exist largely in the bones, 

 muscles, blood, and milk of animals, exist also in 

 plants; whilst the starch, gum, sugar, and oils 

 which constitute fat, and are the elements of respi- 

 ration, are likewise found, ready formed, in vegeta- 

 bles. The proportions, however, in which these 

 exist vary in different classes of plants, and hence 



the different results which we experience from the 

 use of different kinds of food. Growing animals 

 require a different dietary from those which are fat- 

 tening for the butcher, in order to effect the results 

 which we are desirous of producing. Thus, in the 

 former, we wish to build up the bony structure, 

 and to insure a full muscular development ; whilst 

 in the case of the animal preparing for the butcher, 

 we must draw largely not only on the flesh- 

 producing elements of food, but also on the non- 

 nitrogenous or fat-forming classes. There must, 

 however, at all times be a proper mixture of the 

 elements of nutrition and of respiration, otherwise 

 there will be a failure. If an animal is fed 

 exclusively on one description of food, one, for 

 example, which contains merely the elements of 

 nutrition — that is to say, if the food only produces 

 flesh— the animal so fed would gradually sink and 

 die, in consequence of the absence of those 

 elements which are necessary for maintaining the 

 temperature of the body and the production of fat. 

 In like manner, an animal cannot exist on non- 

 nitrogenized food, such as starch, gum, or sugar, 

 which consists merely of the elements of respira- 

 tion, without any of the flesh-forming principles. 



The following table exhibits the elements— first, 

 of nutrition, as existing in plants, and in the flesh, 

 blood, skin, wool, hair, and horn of animals ; and, 

 next, the elements of fat and respiration. The 

 similarity which exists in the composition of the 

 substances in each class shows the close affinity 

 they bear to each other. In the composition of fat, 

 indeed, there is a considerable difference in some 

 respects from that of starch, gum, and sugar ; the 

 cause of which is, that whilst the three last-named 

 substances— starch, gum, and sugar— do promote 

 the production of fat, it is only when in excess that 

 they do so, their primary operation being to 

 support respiration and animal heat. They all 

 agree, however, in not containing nitrogen : — 



The composition of bones is nearly identical with 

 that of skin, &c. 



One of the most common practical errors which 

 we meet with, in the care of animals, is the total 



absence of, or insufficient shelter allowed to them. 

 It is an error, because it involves a waste of food. 

 This will be seen when we consider what respiration 

 implies, and the effects which it produces. 



