MAINTENANCE OF FARM ANIMALS 63 



equilibrium. Contrary to the observations of some of the earlier inves- 

 tigators, no ill effects followed this small supply of protein. Wintering 

 cattle on feeds poor in crude protein straw, inferior hay, corn stover, 

 etc. as practiced by many farmers, confirms this finding. 



In general, it is not wise to supply only the theoretical minimum of 

 protein to animals for extended periods for the following reasons: As 

 we have seen (81, 85), it is essential to make some allowance for the 

 difference in composition of feeding stuffs and the varying capacities of 

 animals to digest and utilize the nutrients in the ration. Besides supply- 

 ing protein to replace the daily waste from the organs of the body, suffi- 

 cient must also be given to maintain the growth of the nitrogenous hair, 

 hoofs, wool, etc. When the ration has too wide a nutritive ratio, the 

 digestibility of the feed is decreased. Moreover, certain proteins of 

 unbalanced composition fed as the sole source of nitrogen will not suffice 

 to maintain an animal. For example, in numerous experiments animals 

 have never been maintained successfully on gelatin, which lacks two ami- 

 no acids and contains only small amounts of others. As we have little 

 knowledge concerning possible deficiencies in the mixture of proteins 

 supplied in the different individual feeding stuffs, it is advisable to make 

 allowance for waste which may occur if the feed contains low amounts 

 of some of the amino acids essential for maintenance. It is also a well- 

 known fact that in general protein is a cell stimulant, and a supply 

 somewhat above the minimum promotes the well-being of the animal. 



The wisdom of not attempting to limit the protein supply to the theo- 

 retical minimum for long periods is shown by the experience of Haecker 10 

 of the Minnesota Station. During many years of patient study he found 

 that dairy cows under good care and otherwise liberal feeding would for 

 long periods continue a good flow of milk on a surprisingly small allow- 

 ance of crude protein. After some years of such feeding, however, their 

 vitality was so depleted that they became physical wrecks long before 

 their time. These studies led Haecker to raise the amounts of crude 

 protein in his feeding standards for the dairy cow above his earlier 

 allowances, tho his recommendations are still below the Wolff -Lehmann 

 standard, as is shown elsewhere. (182) 



Even when sufficient protein is fed to insure good health, the amount 

 required to maintain mature resting animals is not large compared with 

 the need of carbohydrates and fat for body fuel. Maintenance rations 

 for such animals may therefore have a relatively wide nutritive ratio. 

 For example, Kellner recommends for the maintenance of the mature ox 

 at rest a supply of 0.6 to 0.8 Ib. of digestible protein per 1,000 Ibs. live 

 weight. Armsby places the maintenance requirements for both the horse 

 and the ox even lower, recommending but 0.5 Ib. digestible protein per 

 1,000 Ibs. live weight in his standards for maintenance. (172) 



94. Can amids replace proteins ? It has previously been explained that 

 the amids include those nitrogenous compounds which are less complex 



"Minn. Buls. 71, 79, 140. 



