Screening exogenous fibrolytic enzyme preparations for improved in vitro digestibility of bermudagrass haylage

Abstract

Our objectives were to evaluate the effects of 12 exogenous fibrolytic enzyme products (EFE) on ruminal in vitro neutral detergent fiber digestibility (NDFD) and preingestive hydrolysis of a 4-wk regrowth of bermudagrass haylage (BH), to examine the accuracy of predicting NDFD with EFE activity measures, and to examine the protein composition of the most and least effective EFE at increasing NDFD. In experiment 1, effects of 12 EFE on NDFD of BH were tested. Enzymes were applied in quadruplicate to culture tubes containing ground BH. The suspension was incubated for 24 h at 25 °C before addition of rumen fluid media and further incubation for 24 h at 39 °C. The experiment was repeated twice. In addition, regression relationships between EFE activity measures and NDFD were examined. Compared with the values for the control, 9 EFE-treated substrates had greater NDFD (37.8 to 40.4 vs. 35.6%), 6 had greater total VFA concentration (59.1 to 61.2 vs. 55.4 mM), and 4 had lower acetate-to-propionate ratios (3.03 to 3.16 vs. 3.24). In experiment 2, EFE effects on preingestive fiber hydrolysis were evaluated by incubating enzyme-treated and untreated bermudagrass suspensions in quadruplicate for 24 h at 25 °C and examining fiber hydrolysis measures. Compared with values for the control, 3 EFE reduced neutral detergent fiber concentration (62.8 to 63.7 vs. 67.3%), 10 increased release of water-soluble carbohydrates (26.8 to 58.5 vs. 22.8 mg/g), and 8 increased release of ferulic acid (210 to 391 vs. 198 μg/g). Regression analyses revealed that enzyme activities accurately [coefficient of determination (R(2)) = 0.98] predicted preingestive hydrolysis measures (water-soluble carbohydrates, ferulic acid), moderately (R(2) = 0.47) predicted neutral detergent fiber hydrolysis, but poorly (R(2) ≤ 0.1) predicted dry matter and NDFD. In experiment 3, proteomic tools were used to examine the protein composition of the most and least effective EFE at improving NDFD. Relative to the least effective, the most effective EFE at increasing NDFD contained 10 times more endoglucanase III, 17 times more acetylxylan esterase with a cellulose-binding domain 1, 33 times more xylanase III, 25 times more β-xylosidase, and 7.7 times more polysaccharide monooxygenase with cellulose-binding domain 1 and 3 times more swollenin. The most effective EFE had a much greater quantity of fibrolytic enzymes and key proteins necessary for hemicellulose and lignocellulase deconstruction. This study identified several EFE that increased the NDFD and in vitro fermentation of 4-wk BH and revealed why some EFE are more effective than others.

Symposium review: Technologies for improving fiber utilization

“…Limited understanding of the composition and mode of action of EFE has restricted the development of effective EFE preparations that consistently improve fiber digestion and the performance of cattle (Beauchemin and Holtshausen, 2010;Adesogan et al, 2014). The effects of EFE on forage nutritive value are influenced by various factors including the dose, activity, and composition (Eun and Beauchemin, 2007), proteomic profile (Romero et al, 2015a), prevailing pH and temperature (Arriola et al, 2011a), presence of metal ion cofactors (Ca 2+ , Co 2+ , Fe 2+ , Mg 2+ , and Mn 2+ ; Romero et al, 2015b), animal performance level (Schingoethe et al, 1999), and the dietary fraction to which the EFE is applied (Dean et al, 2013).…”

“…The effects of EFE in ruminant diets can be classified as pre-ingestive, ruminal, and postruminal (McAllister et al, 2001). When EFE are applied to fibrous substrates before feeding, fiber hydrolysis can be observed as partial solubilization of NDF and ADF and release of sugars and free or monomeric hydroxycinnamic acids (Krueger et al, 2008b;Romero et al, 2015c), which may contribute to improvements in in vitro fiber digestibility (Romero et al, 2015a) and microbial growth (Forsberg et al, 2000). Furthermore, pre-ingestive hydrolysis seems to cause structural changes ("digestive pits") that make the feed more amenable to further degradation, even when substrates were autoclaved and washed before treatment (Nsereko et al, 2000).…”

RUMINANT NUTRITION SYMPOSIUM: Improving cell wall digestion and animal performance with fibrolytic enzymes1

“…In Exp. 1, 18 EFE from 5 companies were evaluated for their effect on 24-h NDFD of a 4-wk regrowth of Tifton 85 bermudagrass haylage (Romero et al, 2011b). The suspensions were incubated at 25°C for 24 h before addition of buffered rumen fluid (39°C) and further incubation for 24 h in 3 runs.…”

Efeitos de enzimas fibrolíticas sobre a degradação in situ da matéria seca e da fibra de forrageiras

“…A inclusão de enzimas fibrolíticas pode complementar as atividades de enzimas endógenas do rúmen, auxiliando na quebra de frações fibrosas dos alimentos (Martins et al, 2007;Gandra et al, 2017). Resultados como a melhoria da disponibilidade de nutrientes (Romero et al, 2015) e da degradação de frações fibrosas em forrageiras Ibañez et al, 2010) assim como aumento na produção de leite e teor de gordura (Lewis et al, 1996) e do ganho de peso em bovinos de corte (Beauchemin et al, 1995), comprovam o potencial de uso de preparações enzimáticas na dieta desses animais. No entanto, alguns trabalhos relatam que não há efeito positivo da suplementação enzimática sobre a digestão de nutrientes (Yang et al, 2000) e desempenho de vacas leiteiras (Peters et al, 2015;Silva et al, 2016), podendo essa ausência de resposta ser atribuída a especificidade das enzimas utilizadas.…”

“…Já existe a possibilidade do uso de enzimas fibrolíticas comprovadas na alimentação de ruminantes. Todavia, são necessários estudos que auxiliem na compreensão da forma como as enzimas interagem com outras forrageiras, pois a maioria dos estudos foram feitos com dieta a base de forragens temperadas (Beauchemin et al, 2003;Romero et al, 2015). As amostras dos alimentos foram pré-secas à 60ºC durante 72 horas, processadas em moinho de facas com peneira com crivos de 1 e 2 mm.…”