Date of Cut vs. the Combination of Crude Fiber and Crude Protein as Estimators of Forage Quality

The relationship of the dates-of-cut of 22 alfalfa and grass hays grown in Delaware with their digestibilities by sheep were calculated to be represented by the regression equations: Ŷ=73.24−.24X±4.18 All hays Ŷ=75.4 7−.30X±3.36 Harvested prior to June 19 Ŷ=percent dry matter digestibility and X= number of days after April 15. The correlation coefficients were r=−.68 and r=−.74, respectively. Relationships were compared for forage quality estimations made by the date-of-cut equation for New York State: Ŷ=85.0−.48X X=number of days after April 10 (Reid et al., 1959) and estimations of TDN content by the equation: Y=percent TDN content, X1=percent digestible protein, and X2=percent crude fiber (Axlesson, 1952); percent digestible protein =0.946 times crude protein −3.52 (Holter and Reid, 1959). Both methods estimated dry matter digestibilities of the Delaware forages fairly well. The differences from the observed digestibility of dry matter with hays harvested within 70 days of April 10 averaged −.1±0.9 and −1.7±0.9 for the two methods, respectively. With the hays used in this study there was no advantage in accuracy of determination of one method over the other. Ease, speed and practicability of determination seem to favor the method of date-of-cut for evaluating quality of forages cut during 70 days after April 10. The knowledge of daily decrease of 0.3 percentage units in dry matter digestibility of first cutting hays will be of practical value in farm extension programs.