PSIX-18 - A meta-analysis on undigestible neutral detergent fibre as a predictor for feedlot cattle performance and carcass characteristics

Abstract: Undigestible neutral detergent fibre (uNDF) is a non-nutritive component of the diet representing the portion of neutral detergent fibre (NDF) that is not digested. The uNDF amount affects ruminal fill, passage rate, diet digestibility, and cattle performance. Therefore, a meta-analysis was conducted to evaluate the potential use of dietary uNDF to predict finishing feedlot cattle performance and carcass characteristics. A specific search string was used to obtain 22 eligible experiments forming a database in which models were developed. The search string used was as follows “(feedlot OR beef) AND (forage OR roughage OR iNDF OR uNDF) AND (dressing percentage OR dressing %) AND (liver abscess) AND (feed efficiency OR GF OR FG) AND (DMI) AND (ADG) AND (rumen pH OR ruminal pH OR reticulo-ruminal pH)”. Due to the lack of measurement and reporting of uNDF in the literature, the dietary uNDF of each treatment included in the meta-analysis was estimated using data from the Cumberland Valley Analytical Services database. A comparison of uNDF and NDF as predictor variables of performance was also assessed. Models were developed using a mixed model approach, where experiment was modelled as a random effect. Models with dry matter intake (DMI), implant or tylosin as driving variables alongside uNDF concentration or uNDF intake lowered the root mean square prediction error (RMSPE) and improved the concordance correlation coefficient (CCC). The comparison of uNDF and NDF as predictors of outcomes demonstrated more accurate predictions with uNDF as the driving variable. Developed models from this meta-analysis can reasonably predict average daily gain, DMI, dressing percentage, final body weight, dressing percentage, feed efficiency, and hot carcass weight in healthy Bos taurus feedlot cattle. Results suggest there is still more to be discovered about uNDF and its impact in diets for finishing cattle and that uNDF may be a more informative metric than NDF alone. Further research to improve the characterization of forage in the diets of beef cattle is recommended.