The use of the in vitro flter bag method for predicting digestibility of forages * J. Ludwin 1 , Z.M. Kowalski 1 and M.R. Weisbjerg 2 1 Agricultural University of Cracow, Department of Animal Nutrition Al. Mickiewicza 24/28, 30-059 Kraków, Poland 2 Danish Institute of Agricultural Sciences, Department of Animal Nutrition and Physiology, Research Centre Foulum DK-8830 Tjele, Denmark ABSTRACT The possibility of predicting the in vivo organic matter digestibility of forage by estimating in vitro digestibility using either rumen fuid or cellulase as incubation media in the flter bag method was studied. The in vivo OM digestibility of 35 forage samples was determined on 6 rams and in vitro digestibility was determined by two methods: rumen fuid (in a Daisy II Incubator)-neutral detergent (RF-ND) or cellulase solution (also in a Daisy incubator)-neutral detergent (C-ND). The coeffcients of correlation between in vivo digestibility and that estimated by the RF-ND and C-ND methods were 0.62 and 0.69, respectively. Regression analysis shows that both tested methods have good potential for predicting in vivo OM digestibility. KEY WORDS: in vitro, digestibility, forages, flter bag method INTRODUCTION The flter bag method developed by Ankom (Ankom Co, Fairport, NY) is a good alternative to classical in vitro digestibility methods. Most studies have used buffered rumen fuid as the incubation medium (e.g., Mabjesh et al., 2000; Wilman and Adesogan, 2000), but this method has its limitations related to standardizing rumen fuid. Recently, the use of enzymes (cellulase and xylanase) instead of rumen fuid has been studied (Ludwin and Kowalski, 2004). The aim of the present study was to determine the possibility of predicting in vivo forage organic matter digestibility by in vitro digestibility estimated using either rumen fuid or cellulase solution as the incubation medium in the flter bag method. * Supported by the Ministry of Scientifc Research and Information Technology, Grant No. P06E 062 26 1 Corresponding author: e-mail: rzkowals@cyf-kr.edu.pl Journal of Animal and Feed Sciences, 14, Suppl. 1, 2005, 571–574