the quality (DDM value) of the forage declines, increased amounts or 

 higher quality of grain must be fed to prevent reduced milk production. 



Fourth, the weather pattern (the combination of clear and rainy 

 days) during the forage harvesting period influences the length of the 

 harvesting season. Thus, the quality and quantity of forage harvested 

 varies in response to the length and frequency of rain-free day periods 

 during the harvesting season. 



Recent research in dairy nutrition summarizes the effect that date 

 of cut has upon nonrow crop forage as follows:^ 



The date at which first growth forage is harvested is the 

 major known determinant of the intake and digestibility of 

 forage by ruminants. At least within a given climatic 

 region, the digestibile energy (or matter) value of first- 

 grown forage can be predicted quite accurately. Species of 

 plant, methods of preservation (provided that leaf loss 

 is not disproportionate) , and physiological growth stage 

 ; have very little or no effect upon the relationship between 



cutting time and the DDM value (digestible dry matter 

 value) of forage. 



As growth approaches maturity, the DDM value of after- 

 math forage declines much more slowly that that of first- 

 growth forage. Regardless of its stage of growth, aftermath 

 forage has a lower DDM value than first growth forage 

 harvested prior to June 10 in the northeastern states. 



Colovos reports that "The decrease in digestibilities of dry matter, 

 protein, energy, and total digestible nutrients averaged about one-half 

 of 1 percent per day of delay after the first of June.""* This study was 

 done using dairy steers rather than milk cows. Assuming that the same 

 relation holds, this research indicates that if the DDM value from 

 sources other than forage is held constant, the milk produced from a 

 unit of early-cut forage will be greater than from a unit of late-cut 

 forage. Also, milk obtained from a unit of aftermath forage will not be 

 as much as from a unit of "first-cut" harvested before June 10. ^ Milk 

 output per cow, on the other hand, will be greater from a unit of after- 

 math forage than from "first-cut" harvested after June 10. The decline 

 in milk production as the date of cut advances occurs because: (1) the 

 cows will not consume as much (unit weight) of the late-cut forage as 

 they will of the early-cut forage, and (2) the DDM value per unit of 

 forage consumed declines as the date of cut advances. These calendar 

 time periods as reported are applicable to conditions in the North- 

 eastern part of the United States. 



3 Reid, J. T., et. al., "Our Industry Today: Effect of Growth Stage, Chemical 

 Composition and Physical Properties on Nutritive Value of Forage," Journal of Dairy 

 Science, 42:567, 1959. 



^ Colovos, N. F., et. al.. The Effect of Nitrogen Fertilization and the Rate of 

 Harvest on Yield, Persistency, and Nutritive Value of Bromegrass Hay, U. Nutritive 

 Value, New Hampshire Agr. Expt. Sta. Bui. 472, p. 15, 1961. 



"5 First cut is first growth forage. 



