Development of an in vitro incubation technique for the estimation of the utilizable crude protein (uCP) in feeds for cattle.

An in vitro incubation technique based on the first stage of the in vitro digestion technique published by Tilley and Terry (1963) was developed to estimate the utilizable crude protein (uCP) of single feeds and feed mixtures as non ammonia-N after 24 h of incubation. The results of 25 feed samples showed that there was a significant relationship between the uCP values calculated by regression based on in vivo data sets (Y, CP [g.kg-1 DM]) and those measured by the in vitro incubation technique (X, CP [g.kg-1 DM], 24 h incubation): y = 0.85x + 18.0, r2 = 0.84, P < or = 0.001. It was concluded that it can be possible to determine the uCP value of single feeds or feed mixtures by this in vitro incubation technique and to estimate the uCP value of feeds by this regression equation.