The development and application of fecal indexes for predicting dry matter intake, dry matter digestibility and fecal dry matter output

Analytical analyses were conducted upon thirty-six fecal samples obtained from two digestion trials to determine Dry Matter, Nitrogen, Acid Detergent Fiber, Acid Detergent Lignin and Urobilinogen. In addition, individual in vivo Digestible Dry Matter was calculated from total fecal collection procedures. A technique was developed for quantitative urobilinogen analysis of dried fecal samples. From these independent variables cited, and the independent variable animal weight, equations were developed for predicting Fecal Dry Matter Output, Dry Matter Intake, Digestible Dry Matter, and Digestible Dry Matter Intake. A prediction equation was developed which accounted for over 43 percent of the variation in Fecal Dry Matter Output (P'< 0.0003). The equation included the independent variable Urobilinogen. Acid Detergent Lignin, and Animal Weight. It was found that 78 percent of the variation in Dry Matter Intake (P < 0.0001) could be explained by an equation containing the independent variables Nitrogen, Acid Detergent Lignin, and Urobilinogen Cubed. An equation including the independent variables Nitrogen, Acid Detergent Lignin, Acid Detergent Fiber, and the Natural Log of Urobilinogen explained 67 percent of the variation in Digestible Dry Matter (P < 0.0001). Digestible Dry Matter Intake was found to be the most predictable of all the dependent variables studied. Almost 83 percent of the variation in Digestible Dry Matter Intake (P < 0.0001) was accounted for by an equation containing the independent variables Nitrogen, Acid Detergent Fiber, and Urobilinogen Cubed. The large amount of explainable variation in the dependent variables considered in this study was achieved by using different regression equations for each dependent variable to be predicted. It was concluded, therefore, that no one fecal index could best explain the variation in all dependent variables of interest. Rather, several fecal indexes must be employed if more than one dependent variable is to be predicted. The value of fecal indexes in the evaluation of grazed forages is supported by the results of this study.