Effect of exogenous fibrolytic enzymes on in vitro digestibility of cell wall of alfalfa (Medicago sativa) or rye-grass (Lolium perenne)

This study was done to evaluate in vitro degradation of exogenous fibrolytic enzymes and its effects on in vitro degradation of NDF and ADF of alfalfa or rye grass hay. First phase of Tilley and Terry (0, 3, 6, 12, 24, 48 and 72h) was carried out using McDougall saliva alone (S) or with rumen fluid (RF). Enzyme (E) disappearance was constant from 0 to 6h, then increased from 12 to 72h. Concentration of N-NH4 was constant during the first 24h and its highest value was reached at 72h. Forages NDF disappearance was increased from 6 to 72h by E, and from 24 to 72h by E + RE Besides, E increased ADF disappearance from 3 to 72h for alfalfa and from 3 to 12h for rye grass; however, E + RF did not change ADF disappearance. The effect of E + RF was to increase NDF net disappearance of both forages at 48 and 72h, and to reduce ADF net disappearance of rye grass at 12h, without changing that of alfalfa. For the first 12h there was no digestion of the enzymes of the exogenous fibrolytic enzymatic product, which has an important positive effect on in vitro cell wall digestibility of alfalfa and rye grass, even when ruminal microorganisms are present.