20 BULLETIN 459, U. S. DEPARTMENT OF AGRICULTURE. 



to estimate the conditions which will modify the feed requirements 

 of his particular animals and cause his feeds to vary from the aver- 

 age, and, second, in the skill with which he can interpret the daily 

 results and modify his feeding in accordance with them. 



The problems given on the following pages are intended simply 

 as illustrations of the method of using the tables and not as model 

 rations. Limitations of space forbid the multiplication of examples, 

 but the reader who grasps the method will have no serious difficulty 

 in applying it to his own conditions, while facility will be acquired 

 with surprising rapidity by practice. It will be observed that the 

 form of these tables and the methods of computation do not differ 

 materially from those which have been used for many years in com- 

 puting rations on the basis of "digestible nutrients." although the 

 significance of some of the figures is different. It may be added that 

 the digestible protein in the tables is true protein — that is, it does 

 not include the so-called "amids" of the "crude protein." Con- 

 sequently the percentages, as well as the amounts estimated in the 

 rations on succeeding pages, are somewhat smaller than in the older 

 tables. 



TOTAL FEED REQUIRED. 



A bunch of "feeders" 2 to 3 years old, averaging 1,000 pounds per 

 head and in better than average condition, are to be fattened on 

 clover hay and corn-and-cob meal. Such cattle, if of good grade, 

 should weigh 1,400 pounds each when ready for market and should 

 not require over 200 days to make the gain of 400 pounds. They 

 should therefore make an average gain of 2 pounds per day. 



It may be estimated that a gain of 1 pound live weight by animals 

 of this grade will require about 3.5 therms of net energy value in the 

 feed; for a daily gain of 2 pounds, therefore, the requirement would 

 be 7 therms. To this must be added the maintenance requirement, 

 which will increase as the animals grow heavier. For the average 

 weight of 1,200 pounds it is sufficiently accurate to use the mainte- 

 nance requirement computed in the table on page 14 for 1,250 pounds, 

 viz, 7 therms. This makes the total net energy requirement per day 

 14 therms on the average of the whole feeding period. 



If we assume that 2 pounds of grain will be fed for each pound of 

 hay, it is easy to compute from the figures in the last column of the 

 table on pages 11-13 the amount of feed required to supply 14 therms 

 of net energy, as follows : 



Therms. 



In 100 pounds of average clover hay 38. 68 



In 200 pounds of corn-and-cob meal 151. 60 



In 300 pounds of feed , 190. 28 



In 1 pound of feed ' . 634 



