THE FEED REQUIREMENTS OF FARM ANIMALS 149 



These results, obtained from careful, independent investiga- 

 tion, agree with each other remarkably well and their average 

 probably represents the requirements for milk production 

 as closely as they may be represented by a mathematical 

 expression. 



Requirements for Wool Production. — Inasmuch as wool 

 is composed largely of protein, a small amount of protein 

 is necessary for wool production. Armsby,^ after reviewing 

 the available experiments, concludes that 0.14 lb. of protein 

 daily per 1000 pounds live weight should be added to the 

 other protein requirements for wool production. In ex- 

 periments by Grindley, Emmett, Coffey, and Bull at the 

 Illinois Station,^ feeding large amounts of protein did not 

 produce any more wool in the case of fattening lambs than 

 when only a medium amount was fed. When sheep in good, 

 thrifty condition receive sufficient nutrients for the other 

 functions of the body, it is probable that the additional re- 

 quirements for wool production may be neglected. 



The Feed Unit System of Calculating Rations. — Although 

 it has been used but httle in this country, the feed unit 

 system is used quite extensively in Denmark, where it origi- 

 nated, and in other Scandinavian countries. It is used 

 almost entirely for dairy cows, though to a slight extent for 

 the other classes of farm animals. 



Unlike the other standards already discussed, the feed 

 unit system does not take into account either the total 

 digestible nutrients or the net energy values of the feeds. 

 Instead, the different feeds, after many carefully conducted 

 feeding experiments, were given equivalent values, regarding 



1 U. S. Dept. of Agr. Bur. of Anim. Ind. Bui. 143. 

 ' Unpublished data. 



