FEEDING STANDARDS— CALCULATING RATIONS 101 



when protein-rich feeds are comparatively cheap, the dairyman may 

 well feed as heavy an allowance as Savage and Eckles recommend. 

 Even these amounts are lower than called for in the original Wolff- 

 Lehmann standards. The skilled dairyman will adapt the amount of 

 concentrates fed to the productive ability of each cow, not compound- 

 ing a different ration for each animal, but will balance the ration for 

 the average of the herd and then feed the cows as much roughage as 

 they will consume and concentrates in proportion to the milk or butter 

 fat produced by the several cows, as is explained in Chapter XX. 



VI. ^Modified Wolff-Lehmann Standards 



Methods of computing rations compared.— In this chapter it has 

 been pointed out that valuing feeds for productive purposes on the 

 basis of their net energy content, is theoretically more accurate than 

 the Wolff-Lehmann method of comparing them in terms of the 

 digestible nutrients they furnish. Unfortunately, the net-energy 

 values have been determined for but a few feeds, and with these only 

 for the fattening steer. For other feeds and other classes of animals, 

 the values which may be computed are but approximations. On the 

 other hand, during the last half-century scores of thousands of analyses 

 of feeding stuffs have been made, as shown in Appendix. Table I, and 

 large numbers of digestion experiments have been conducted in which 

 the coefficients of digestibility have been determined, as given in Appen- 

 dix Table II. Thus, the values for digestible nutrients in the various 

 feeding-stuffs, given in Appendix Table III, rest on a reasonably secure 

 basis, tho we must remember that different kinds of animals digest 

 somewhat different percentages of feeds, especially of roughages. 



The value of a concentrate and of a roughage for productive purposes 

 cannot be compared on the basis of the digestible nutrients each fur- 

 nishes, for in the roughage, containing more fiber, a larger part of the 

 energy in the digested nutrients is used up in the non-productive work 

 of mastication, digestion, and assimilation. In the ordinary rations 

 for each class of animals, concentrates and roughages are, however, 

 usually fed in about the same proportions. This tends to lessen any 

 error due to inaccuracy in computing rations according to the Wolff- 

 Lehmann method. 



Furthermore, in this method a definite amount of dry matter is pre- 

 scribed. If a ration contains sufficient digestible nutrients to meet the 

 Wolff-Lehmann standards, but carries too much dry matter, obviously 

 too much roughage or concentrates too high in fiber have been used, 

 and the net-energy value will consequently be too low. On the other 

 hand, if the content of digestible nutrients satisfies the standard, while 



