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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 I, 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 (I = .63) and diet in vivo digestibility (r = .33). Diet nitrogen % was highly correlated with fecal nitrogen % (r = .81) and fecal acid pepsin disappearance % (r = .%3). 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 1.71, dietary nitrogen deficiencies should be suspected.

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An experiment examining the relationships between dietary and faecal phosphorus (P) concentration and intake and faecal output of P by steers is described. Six forages with a wide range of chemical properties were fed to six steers in a Latin square design. Dietary P concentration was highly associated with faecal P concentration in simple linear regression equations including (r2= 0.91) and excluding (r2= 0.94) animal variation. The regression slopes were similar to those in an Australian study involving dairy cows. However, the intercept values for the two studies differed. Phosphorus intake was well associated with daily faecal P output. Another study in Australia with steers showed similar results. However, the linear regression equation in the present study differed from that in the Australian study. Therefore, the application of a generalized equation to predict P intake from faecal P output is not advocated until the reliability of the equation in this study is confirmed with other forages.