EXPERIMENT STATION BULLETINS. 



255 



hydrates, or nitrogen-free extract as they are here called, and 3.96 

 pounds of fat. 



Let us suppose next that the dung for these six days is weighed, 

 sampled and analyzed. It would weigh not far from 25 pounds per day 

 per steer, or 150 pounds for the six days. A chemical analysis would 

 show that this dung contained, per hundred pounds, 4.702 pounds of 

 protein, 10.55 pounds of crude fiber, 11.89 pounds of nitrogen-free 

 extract and 1.373 pounds of fat. The hundred and fifty pounds of this 

 material would contain 7.08 pounds of protein, 15.77 pounds of crude 

 fiber, and 17.83 pounds of nitrogen-free extract and 2.06 pounds of fat. 

 These materials having passed through the body and been excreted from 

 it unaltered, could not have been digested. If therefore, we subtract the 

 amounts of each nutrient in the dung from the amounts of the same 

 material in the food consumed we shall have the amount digested, the 

 amount taken out of the food by the digestive organs of the animal and 

 utilized in its growth or maintenance. This is done in the following 

 table. 



In 120 pounds hay 



In the 1«0 pounds dung 



Amounts digested 



Protein. 



lbs. 



14.76 



7.08 



7.68 



Crude 

 fiber. 



lbe. 



29.76 

 15.77 



13.99 



N. free 

 extract. 



lbs. 



45.72 

 17.83 



27.89 



Fat. 



lbs. 



3.96 

 2.06 



1.90 



Taking the protein as ah example, we can determine the proportion of 

 it digested by dividing the 7.68 pounds by the weight of it given in the 

 feed, 14.76 pounds, the result would be 52, the per cent of protein of 

 clover hay digested by the steer. In the same way the per cents digested 

 of the other constituents of the ration are found. This would be for crude 

 fiber 47 per cent, for nitrogen-free extract 61 per cent, and for fat 48 per 

 cent. Results thus obtained are called digestion coefficients. The digestion 

 coefficient of the protein of clover hay is 52. The digestion coefficient of 

 crude fiber in this experiment would be found in the same way to be 47, 

 that of the nitrogen-free extract 61 and that of the fat 48. 



The two steers are fed and treated exactly alike. If both animals are 

 normal and healthy and no mistakes are made in the prosecution of the 

 experiment, the digestion coefficients found by one steer should coincide 

 very ctosely with those found by the other. Repeated experiments have 

 shown that cows do not differ much as to the amounts of protein, carbo- 

 hydrates and fat they can digest from the same material. The digestion 

 coefficients found by one animal therefore will hold good approximately 

 for all other animals of the same species. It is not true on the other 

 hand, that the digestion coefficients of one fodder will apply to any other. 

 For instance, while but 52 per cent of the protein of red clover is digesti- 

 ble by cows, 73 per cent of the protein of pasture grass was found 

 digestible in Pennsylvania, while of timothy less than half the protein 

 was found digestible at the Maine and Utah Experiment Stations. Of 

 the protein of corn silage about 53 per cent is digestible. The protein 

 •f linseed meal is much more digestible, fully 87 per cent of it being 



