A New Indicator Method for the Determination of Digestibility and Consumption of Forages by Ruminants

Summary Mixed forage of the same source cured by barn, oven and field drying and by ensiling, hay consisting largely of Ladino clover, and pasture grass (largely timothy) at three different growth stages were fed to wethers and/or bull calves and/or steers in 36 conventional digestion trials. The dry matter digestibility of these forages ranged from 48.2 to 72.9 per cent. Spectral examinations of acetone extracts of the forages studied and their corresponding fecal products revealed that some chromogen(s) absorbing light at 406 m μ was completely recoverable in the feces. The average rate of recovery of the chromogenic substance(s) in the feces of animals fed the forages used in these studies was 100.5 per cent for the 36 trials. As a result of these studies, a simple, accurate method employing the chromogen(s) absorbing light at 406 m μ as a reference substance was devised for the estimation of digestibility and consumption of forages by ruminants. This method apparently has a wide range of applicability in nutrition studies with ruminant animals, especially in the study of pastures where a direct measure of consumption is impossible.