Topical Cellulase Application Effects on Tall Fescue Digestibility

Two studies were conducted to assess the effects of topically applying a prepared cellulase solution (PCS) as a forage pretreatment to increase digestibility of tall fescue ( Festuca arundinacea Schreb.). Fall regrowth and stockpiled tall fescue were harvested from the field (Mexico silt loam: fine montmorillonitic mesic Udollic Ochraqualf) and studied in laboratory Exp. 1 and 2, respectively. Experiment 1 involved topical application of 40 mL of PCS to 100 g (on a dry‐matter basis) dried and fresh leaf material that had either been chopped or remained whole. Further treatments involved 1‐, 6‐, or 12‐h drying times post‐application and freezing to curtail enzymatic activity or no freezing. Experiment 2 involved whole and chopped fresh leaf material with a surfactant treatment added and post‐application drying times altered to 1,12, 24, and 48 h. In vitro dry matter digestibility (IVDMD) of tall fescue was significantly increased (28 g kg −1 ) by topical application of PCS in both experiments. Allowing longer exposure time of herbage to PCS was not an advantage. Addition of a surfactant to PCS decreased IVDMD (36 g kg −1 ) but increased IVDMD (14 g kg −1 ) when PCS was not applied. Allowing the PCS to dry on herbage for 1‐, 12‐, and 24‐h post‐application resulted in significant IVDMD increases compared to no PCS (22,27, and 31 g kg −1 , respectively) while PCS application most benefited IVDMD for 24 h. Scanning electron micrographs revealed cuticular disruption on leaf blades which may be at least partially responsible for increased IVDMD of PCS‐treated samples. These studies indicated that topical PCS treatment can extend existing forage supplies. Further studies under field conditions and animal trials are needed.