• Evaluation of Fecal Indices to Predict Cattle Diet Quality

      Wofford, H.; Holechek, J. L.; Galyean, M. L.; Wallace, J. D.; Cardenas, M. (Society for Range Management, 1985-09-01)
      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.
    • Evaluation of Total Fecal Collection for Measuring Cattle Forage Intake

      Holechek, J. L.; Wofford, H.; Arthun, D.; Galyean, M. L.; Wallace, J. D. (Society for Range Management, 1986-01-01)
      Conventional digestibility trials with steers were conducted to evaluate relationships between actual forage intake and estimated forage intake using the total fecal collection procedure. Actual forage intake of 6 of the 9 forages fed was not accurately estimated by the widely used technique of dividing total fecal output by forage indigestibility estimated by in vitro procedures. This was because 48-h in vitro digestibility poorly estimated in vivo digestibility of 6 forages. Regression equations based on in vivo-in vitro digestibility relationships can reduce but not solve this problem because in vivo processes such as mastication and rumination are bypassed with in vitro techniques. The use of a 36-h microbial digestion period for nongrasses and a 72-96-h microbial digestion period for grasses shows potential to improve in vitro digestibility estimates of cattle in vivo digestibility. Another potential means of improving in vitro digestibility estimates is to select the highest digestibility value from forage or diet samples subjected to 36-, 48-, 60-, 72-, 84- and 96-h microbial digestion periods.