The effects of recombinant bacterial expansin-like protein and a fibrolytic enzyme on in vitro nutrient digestibility and preingestive hydrolysis of alfalfa silage

BLAJMAN, J.E.; PECH-CERVANTES, A.; IRFAN, M.; GONZÁLEZ, C.F.; VYAS, D.; ARRIOLA, K.G.; DI LORENZO, N.; JIANG, Y.; AMARO, F.X.; ADESOGAN, A.T.

Cincinnati

Encuentro; 2019 Annual Meeting of the American Dairy Science Association; 2019

American Dairy Science Association

The aim of this study was to examine if effects of an exogenous fibrolytic enzyme (EFE) on in vitro digestibility and preingestive hydrolysis of alfafa silage can be synergistically increased by different doses of a recombinant bacterial expansin-like protein (BsEXLX1). Treatments were arranged in a 2 × 4 factorial arrangement with two levels of a cellulase-xylanase EFE (0, 2.3 mg/g DM) and four levels of BsEXLX1 (0, 0.106, 0.212, and 0.424 mg/g DM). In Experiment 1 (E-1), dried, ground (1 mm) alfalfa silage samples were preincubated in sodium citrate buffer for 1 h at room temperature in quadruplicate with or without the treatments followed by incubation in rumen fluid for 24 h at 39°C. Gas production (GP), in vitro true digestibility, CH4 emissions, and VFA profile were measured after 24 h. In Experiment 2 (E-2), alfalfa silage was incubated with or without the treatments in deionized water containing 0.02% sodium azide for 24 h at 25°C and preingestive hydrolysis was measured. Data were analyzed using NLME package of R studio with EFE, BsEXLX1 and interaction as fixed effects and run as a random factor in the model. In E-1, EFE increased GP (P = 0.02) and reduced pH (P < 0.01) compared to the control; however, no effects were observed on in vitro DM, NDF, and ADF digestibility. Similarly, the combination of EFE and BsEXLX1 had no effects on digestibility of DM, NDF, and ADF or VFA and NH3-N concentrations. Methane emissions tended to increase with EFE (P = 0.08) treatment while BsEXLX1 supplemented at 0.212 and 0.424 mg/g DM significantly increased CH4 emissions (P < 0.01), compared to the control. During preingestive hydrolysis (E-2), EFE increased DM, NDF, ADF and HEM hydrolysis (P < 0.01); however, no synergistic improvements were observed when BsEXLX1 was added. Adding EFE increased release of reducing sugars compared to control (P < 0.01) but no effects were observed by adding BsEXLX1 (P = 0.80). In conclusion, EFE increased preingestive hydrolysis of alfalfa fiber but adding BsEXLX1 did not synergistically increase the response.