31 



SOME MORE RECENT ASPECTS OF ANIMAL NUTRITION. 



The Composition of Proteins. 



Early investigators in animal nutrition believed that all proteins, in so far as their 

 utilization in the animal was concerned, were alike. More recently, chemists and 

 physiologists have discovered that this is not the case, but that different proteins are 

 made up of complex nitrogenous material which in the process of digestion is broken 

 up into simpler forms known as amino acids, and that these acids vary in kind, depend- 

 ing upon the proteins from which they are derived. It is from these simpler compounds 

 or acids that the animal builds up living tissue, and it is entirely possible that a ration 

 fulfilling all the requirements of a feeding standard may lack some needed acid or 

 acids not present in the proteins of the ration, with the result that the protein in the 

 particular ration proves unsatisfactory for growth. More study will be necessary 

 before definite ad\ice can be given. 



Vitamines. 



It has also been discovered possible to formulate rations which, while they supply 

 sufficient protein and energy, do not promote the normal functions of growth and 

 reproduction on account of the lack of small amounts of certain substances known as 

 vitamines. To the lack of vitamines in the diet are also attributed certain diseases, 

 such as beriberi of tropical countries. 



From the standpoint of animal nutrition it is only necessary to understand that the 

 essential vitamines are to be found both in milk and in the leaves of plants, and only 

 when the animal's diet is very abnormal is the vitamine content likely to prove de- 

 ficient. By feeding very young stock, with more or less milk and fine hay, and the 

 older animals with haj^, pasture grass and grain mixtures, little trouble is likely to be 

 experienced from lack of vitamines. Fresh green material is rich in vitamines. 



Ash Requirements of Milch Cows. 



It has been demonstrated that calcium and phosphorus, particularly the former, 

 are sometimes deficient in rations, and that cows giving a large flow of milk find it 

 impossible to assimilate sufficient mineral matter from the daily ration. Of the feed- 

 ing stuffs commonly used the legume hays, such as clover or alfalfa, beet pulp and 

 pasture grass, are comparatively rich in calcium, and if fed in liberal quantities will 

 usually supply sufficient calcium to fulfill the necessary requirements. The feeding 

 of such inorganic materials as bone meal and calcium chloride does not seem to 

 prove effective in supplying the ash deficienc3^ 



It is not believed that the' newer knowledge thus far secured affects seriously the 

 underlying principles relating to the chemical or energy requirements of animals, but 

 that this knowledge simply supplements such standards. With these facts in mind 

 it may be well to repeat that all proteins are not alike in value, and that a definite 

 amount of one may have a higher degree of efficiency than another; hence certain 



