THE FEED REQUIREMENTS OF FARM ANIMALS 121 



32 of the Appendix. These standards cover the require- 

 ments of practically all classes of farm animals under different 

 conditions. They were presented first by Wolff, a noted 

 German student of animal nutrition, in 1864. In 1896, 

 they were revised by Lehmann, and since have been called 

 the Wolff-Lehmann standards, or sometimes the " German 

 standards." The latter term, however, is somewhat mis- 

 leading as other standards also have been presented by 

 German investigators in animal nutrition. 



The Wolff-Lehmann standards attempt to show the 

 requirements of farm animals under different conditions 

 expressed in pounds of total dry substance, digestible crude 

 protein, digestible carbohydrates, and digestible fat per 

 1000 pounds live weight. The nutritive ratio required 

 by the animal is given also. 



The formulation of a ration, according to any feeding 

 standard, consists essentially of three steps. (1) Having 

 given the requirements for an animal of a given weight, 

 usually 1000 pounds, the requirements of the animal under 

 consideration are determined. (2) A " trial ration " is 

 assumed, using the amounts and proportions of concentrates 

 and roughages which, in the opinion of the feeder, are satis- 

 factory. (3) The trial ration is modified by adding or 

 deducting concentrates or roughages of such composition 

 as to furnish approximately the required amounts of dry 

 substance, digestible protein, digestible carbohydrates, di- 

 gestible fat, and net energy, and the proper nutritive ratio. 



Thus, for example, one calculates a ration according to the 

 Wolff-Lehmann standard for a 1200-pound horse at light 

 work as follows : According to the standard (Table 32, 

 Appendix), the requirements of a 1000-pound horse at Ught 



