Prediction of nutrient composition and in vitro dry matter digestibility from physical characteristics of forages

In order to develop equations to estimate nutrient composition and in vitro dry matter digestibility (IVDMD) of forages from physical characteristics, grasses (timothy, reed canary grass and brome grass) and legumes (alfalfa and red clover) were harvested at different stages of maturity and analyzed for content of nutrient components, and the IVDMD and physical characteristics were determined. Physical characteristics were used to develop multiple regression equations to estimate content of nutrient components (crude protein, acid detergent fibre, neutral detergent fibre, acid detergent insoluble nitrogen and lignin) and IVDMD for each forage. The equations for the grasses included only grinding resistance either in linear or square terms. The regression coefficient (r2 or R2) (P < 0.05) of the equations ranged from 0.5 to 0.94 for timothy, 0.82 to 0.93 for reed canary grass, 0.4 to 0.96 for brome, 0.65 to 0.96 for alfalfa and from 0.71 to 0.97 for red clover. The coefficients of regression (r2) between determined and estimated values for protein and IVDMD of timothy and brome grass were 0.76 and 0.59, and 0.76 and 0.66, respectively. Thus crude protein content and IVDMD of timothy and brome grass can be estimated from grinding resistance of the forages from the respective equations.