i.e., no rain damage and rain damage. ^^ The difference in the nutrient 

 vahie of these forages is reflected in research hy Rakes, et. al.-^ They 

 found that the digestihle dry matter was reduced about 5.3 percent and 

 the vohintary intake about 17.4 percent when forage was rained on as 

 compared to no rain damaged forage. The production surfaces are 

 shown in Figures 12A and 13A, where Figiire 12A represents the daily 

 milk production surface using no rain damaged forage and grain and 

 Figure ISA represents the daily milk production surface using rain 

 damaged forage and grain. Figure 12A needs to be explained since the 

 only difference is the type of forage fed; Figure 13 is self-evident. 



The X and Y axes in Figure 12A represent the pounds of grain and 

 forage available for consumption per cow per day, respectively. The 

 isoquants represent the expected daily milk output per cow resulting 

 from the various combinations of inputs (forage and grain). 



There are 2 sets of isoquants. The solid and broken isoquants repre- 

 sent the milk output per cow per day that can be expected using the 

 combinations of early cut and late cut forage and grain, June 1 and 

 July 10, respectively. The difference in the isoquants reflects the re- 

 sults expressed by Slack, et. ah, "approximately 20 percent more late- 

 cut forage must be eaten to provide the same amount of digestible dry 

 matter."-^ 



The acceptance level lines represent the combinations of forage and 

 grain that the cow will consume per day, if the forage is fed free choice 

 and grain is regulated by date of cut of the forage. The highest feed 

 acceptance level is for June 1 forage and the lowest for July 10. The 

 2 lines converge at 13.6 pounds of forage and 22 pounds of grain. This 

 convergence occurs because the cow will eat a mininnim quantity ( 13.6 

 pounds ) of any type and quality of forage and a maximum quantity 

 (22 pounds) of grain. 



There are 2 oliservations inherent in this analysis. First, the 2 sets 

 of isoquants become identical if time is considered a variable, i.e., June 1 

 isoquants become July 10 isoquants. This should be obvious, since there 

 is a milk production surface for each date of cut represented only by 

 June 1 and July 10. Second, the feed acceptance level lines become 

 identical if time is considered a variable. As date of cut advances, the 

 amount of forage that the cow will consume will decline such that when 

 date of cut is July 10, the coml)inations of forage and grain consumed 

 is expressed by the July 10 acceptance level line. The lowest isoquant in 

 Figure 12A represents those combinations of early cut forage and grain 

 that will produce 25 pounds of milk per cow per day. A possible feed 

 combination may be 3 pounds of grain and 26.8 pounds of forage. If 3 



21 Data were obtained from many sources. For a representative sample, see: 

 Slack, E. T., et. ah. Effect of Chopping on Feeding Value of Hays, Cornell Agr. Expt. 

 Sta. Bui. 950, 1960, and Loosli, J. K., et. al., "The Comparative Value of Ladino Clover. 

 Birdsfoot Trefoil, Timothy and Alfalfa Hays for Yield and Quality of Milk," Journal 

 of Dairy Science, 33:228-236. 



-- Rakes, A. H., et. al.. The Feeding Value for Milk Production of Hays Cut at 

 Various Dates, W. Va. Agr. Expt. Current Rpt. 35. 



23 Slack, S. T., et. al.. Effect of Curing Methods and Stage of Maturity upon Feed- 

 ing Value of Roughages, Cornell Agr. Expt. Bui. 957, 1960, P. 24. 



27 



