2 DIFFERENT-TYPE EQUATIONS ANALYZING DECREASE IN DRY-MATTER DIGESTIBILITY WITH GROWTH OF FORAGES

This study was conducted to present a new equation for analyzing the d ecrease in dry matter digestibility [DDMD] with growth of forage, and to relate it and the previous equation analyzing DDMD (Shimojo et al., 1998b). The following equation showed the relationship between two eq uations, namely, the new equation on the left-hand side and the change d form of the previous equation on the right-hand side. D-1/W-1 . [1 - exp {((RGR) over bar(d) - (RGR) over bar(w)) . (t(2) - t(1))}] = (1 - W-1/W-2) . (D-1/W-1 - (RGR) over bar(d)/RGR(w) . D/W), (A) where W = dry weight of forage (W-1 not equal W-2), D = dry weight of digestible materials (D-1 not equal D-2), (RGR) over bar(w) = mean relative grow th rate of forage, (RGR) over bar(d) = mean relative growth rate of D, (1 - W-1/W-2) = forage growth index [FG index], (D-1/W-1 - ((RGR) ove r bar(d)/(RGR) over bar(w)).(D/W)} = a changed form of DDMPD index (DD MPD index: index for the decrease in dry matter partition into D). The following results were obtained: Equation (A) showed that DDMD was ex pressed using RGR(d) and RGR(w) as main factors in either of two diffe rent-type equations. It was suggested that there was a new equation an alyzing DDMD, and using the new and previous equations some informatio n was obtained for the change in dry matter digestibility with growth of forages.