Evaluation of Fecal Indices to Predict Cattle Diet Quality

Abstract

A study involving 6 feeds of widely varying chemical properties fed to 6 steers in a Latin square design was conducted to evaluate the potential of fecal chemical characteristics for predicting ruminant nutritional status. Forage intake, diet in vivo digestibility %, and diet nitrogen % were used as dependent variables and fecal nitrogen %, nucleic acid %, nonfiber bound nitrogen %, ether extract %, neutral detergent fiber %, acid detergent fiber %, acid detergent lignin %, water soluble material %, and acid/pepsin disappearance % were used as independent variables in regression equations. Forage intake and diet in vivo digestibility could not be accurately predicted from any single variable or combination of independent variables. Fecal acid/pepsin disappearance was the independent variable most highly correlated with forage intake (r = .63) and diet in vivo digestibility (r = .33). Diet nitrogen % was highly correlated with fecal nitrogen % (r = .81) and fecal acid pepsin disappearance % (r = .83). Combined data from this and other studies give a generalized regression equation that shows potential for detecting nitrogen deficiencies in steer diets from fecal N % (organic matter basis) when steer diets contain low levels of soluble phenolics. When steer fecal nitrogen % drops below 1.7%, dietary nitrogen deficiencies should be suspected.