INVESTIGATIONS ON THE METABOLISM OP MILCH COWS. 905 



require for maintenance 1 calorie per hour per kilogram of live weight. 

 If a steer weighing G20 kg. is fed 8 kg. of meadow hay of the composi- 

 tion noted above, the ration would furnish 0.7 kg. of digestible protein 

 and 6.6 kg. of digestible nitrogen-free material (crude fiber plus nitrogen- 

 free extract plus fat multiplied by 2.4) per 1,000 kg. live weight. It is 

 of the utmost importance to determine the amount of hay sufficient for 

 maintenance, since hay serves as the basis of the ration. 



Oat straw contains 85 per cent of dry matter, made up of 0.4G8 per 

 cent of protein, 2.27 per cent of fat, 42.41 per cent of crude fiber, 6.G per 

 cent of mineral matter, 0.525 per cent of nitrogen, and 46.75 per cent 

 of carbon. Using the data furnished by Kellner's experiments, it 

 appears that a maintenance ration can not be made up of meadow hay 

 and oat straw of the above composition without furnishing an excess of 

 nitrogen-free material. In Kellner s experiments a steer weighing 012 

 kg. lost daily 91 gm. of protein and 102 gm. of fat when fed 3.45 kg. of 

 meadow hay (dry matter) and 4.5 kg. of oat straw (dry matter). The 

 coefficients of digestibility of dry matter of hay and straw were shown 

 to be as follows: 



Coefficients of digestibility of dry mailer of hay and straw. 



'Pure protein is calculated by assuming that for each 100 gm. of digesti j'.e dry matter 0.4 gm. of 

 nitrogen due to metabolic products is excreted in the feces. Since the amid compounds are regarded 

 as completely assimilated, it may be assumed that the remaining nitrogen of the feces is proteid 

 nitrogen. Suppose that the food contained 033 gm. of protein, that 4.716 gm. of dry matter was 

 assimilated, and that the dry matter of the feces amounted to 0.2547 gm., containing 1.795 per cent of 

 nitrogen, or 45.72 gm. of nitrogen, the nitrogen due to metabolic products would be 18.80 gm. 

 (47.16X0.4=18.86). The proteid nitrogen in the feces, therefore, would equal 20.80 gin. (45.72 — 18.86 — 

 26.86). This is equivalent to 108 gm. of protein. Therefore the food furnished 465 gm. of digestible 

 protein (633 - 168 = 465). 



Suppose, for instance, it is desired to calculate the quantity of hay 

 and straw (containing 58.5 and 53.2 kg. of digestible nitrogen-free 

 material, respectively) which would furnish 0.7 kg. of digestible pro- 

 tein and 6.6 kg. of nitrogen-free material. Let X gm. equal the hay 

 fed and Y gm. the straw. Then Gl X+l Y=700 gm. of crude protein, 

 and 585 X— 532 Y=G,600 gm. of nitrogen-free material. Solving the 

 equations, X = 11.48 and Y= —0.2. In other words, on the supposi- 

 tion that hay and straw have the composition assigned to them above, 

 a ration furnishing the desired quantities of protein and nitrogen-free 

 material can not be made up from these feeding stuffs, since Y has a 

 negative value. The straw contains too large a percentage of nitrogen- 

 free material and too small a percentage of protein. Therefore the 

 protein of the ration must be chiefly supplied by hay and the nitrogen- 

 free material by straw, which will furnish an excess of the latter. 



