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 
11,100 pounds.of average ‘clover hay- ses) -eeeek oo. oe ee eee 38. 68 
ia200 pounds ‘of. corn-and-cob meal-eee"-.o-- o2- + ee ae ee 151. 60 
in 300 pounds of feed: :..>2>-2eeeeeee ee eee eee 190. 28 
in ‘impound 'of feed... .2 2h ceeeeee ee eee eee she . 634 
