USE OF ENZYMATIC SOLUBILITY WITH FICIN (EC-3.4.22.3) TO PREDICT IN-SITU FEED PROTEIN DEGRADABILITY

The applicability of the plant enzyme ficin (EC 3.4.22.3) for the pred iction of protein degradability of ruminal feeds was examined. Optimum pH and the effect of enzyme concentration, incubation time and amylas e pretreatment for high-starch feeds on protein solubility with ficin (FS) were determined. The predictive ability of ficin assay in the con ditions specified for particular groups of feeds was estimated using 6 1 feeds including protein meals (7), cereal grains (2), silages (9), s ugar beet pulp, dried forages (29) and compound feeds (13) of known in situ effective protein degradability (ED) determined with cows.Optimu m incubation time was 2-3 h, enzyme amount (per 100 mg of crude protei n in feed sample) equivalent to 9 U for compound feeds and concentrate ingredients not treated with amylase, 18 U for forages, Close linear relationships between the in vitro FS (X, %) and in situ estimates of ED (Y, %) were found. The regression equation for all samples (n = 61) was Y = 1.018 X + 1.331, R(2) = 0.92 (P < 0.001), SEE 4.17. After spl itting to forages (FOR) and compound feeds and ingredients (CON) SEEs were 4.25 and 3.56%, respectively. FS values accounted for 85, 92 and 95% of the variation in ED measured in situ for FOR, FOR + CON and CON samples, respectively.