ECONOMIC USE OF FORAGES IN LIVESTOCK PRODUCTION | 
TastE 2.—Forage and grain feed combinations and substitution rates 
in producing 8,500 pounds of 4-percent fat-corrected milk per 
cow * 
Feed combinations for producing 8,500 pounds |Average quantity|Average quantity 
of milk per cow 2 of grain replaced |of forage required | Forage as per- 
e Zig ___| per pound of to replace a centage of total 
forage added 3 pound of grain feed (percent) 
Hay Grain (pounds) (pounds) (pounds) 
Pounds: es 
50005 es =_ - a 6, 154 ! 1. 39 0. 72 | 
SH HOOAMS SIAN MS _ SNS 5, 459 50. 2 
\ 1.13 88 { 
GO00sts. ee 4, 892 55. 1 
\ 94 1. 06 { 
6: 500 Fee te aan bans 4,423 59. 5 
\ 79 1.27 { 
(0002s s2 -. 2 Ve 4,029 63. 5 
\ 67 1. 49 { 
75002 oce cere 3, 694 67. 0 
\ 58 1.72 { 
(C100) ae 6 Re 3, 406 70. J 
\ 50 2. 00 { 
Ua Os Le ee 3, 156 7289 
\ 44 2.27 { 
OOOO ee 2, 937 75. 4 
\ 39 2. 56 { 
OG OOo ea bd: 2, 744 77.6 
\ 34 2.94 { 
10 000ng fee = at 2, 572 79.5 
\ Bl 3, 23 { 
iM OspsS OL OE ei oles 2, 419 81.3 
TRO OOS eis ria hay 2, 281 ae od 82. 8 
1 Based on following regressi IONS Xo — se COUNTS 25 wh XK 
g gression equation: 2= 356K, 8088 where 9 
refers to pounds of grain and X, refers to pounds of forage per cow. 
For further explanation of the derivation of substitution rates and for estimates 
of marginal rates of substitution at specific combinations of forage and grain, see 
Hepapy, Earu O., and Otson, RussEeuu O. (6). 
2 Total feed requirements in terms of TDN are higher for combinations that 
consist of nearly all grain or nearly all forage than for combinations in between 
because the TDN conversion factor for each feed assumes constant rates of sub- 
stitution, whereas the data used in this analysis indicate a diminishing rate of 
substitution. 
3 Derived by dividing the change in pounds of grain by the corresponding 
change in pounds of hay as the forage-grain composition of the ration is varied. 
If the variations in the ration were small, these figures would be essentially the 
marginal rates of substitution at each combination. Where, as in this table, 
changes in the ration are large, the substitution rates derived in this manner are 
averages of the marginal substitution rates between two consecutive combina- 
tions. As small variations in feed rations are not ordinarily practical, the average 
marginal rates shown are refined enough for ascertaining the optimum forage- 
grain combination. 
tion of pork shown in table 3. In this experiment hogs were fed 
varying combinations of ground legume hay and No. 2 yellow corn. 
Columns 1 and 2 show that 100 pounds of pork can be produced with 
a rather wide range of forage-grain combinations. As in the case of 
milk production, each additional increase in forage fed replaces a 
209706—52 2 
