title: Effect of fibrolytic enzymes added to a Andropogon gayanus grass silage-concentrate diet on rumen fermentation in batch cultures and the artificial rumen (Rusitec).
abstract: In vitro batch cultures were used to screen four fibrolytic enzyme mixtures at two dosages added to a 60 : 40 silage : concentrate diet containing the C(4) tropical grass Andropogon gayanus grass ensiled at two maturities - vegetative stage (VS) and flowering stage (FS). Based on these studies, one enzyme mixture was selected to treat the same diets and evaluate its impact on fermentation using an artificial rumen (Rusitec). In vitro batch cultures were conducted as a completely randomized design with two runs, four replicates per run and 12 treatments in a factorial arrangement (four enzyme mixtures×three doses). Enzyme additives (E1, E2, E3 and E4) were commercial products and contained a range of endoglucanase, exoglucanase and xylanase activities. Enzymes were added to the complete diet 2 h before incubation at 0, 2 and 4 μl/g of dry matter (DM). Gas production (GP) was measured after 3, 6, 12, 24 and 48 h of incubation. Disappearance of DM (DMD), NDF (NDFD) and ADF (ADFD) were determined after 24 and 48 h. For all four enzyme mixtures, a dosage effect (P>0.05) DM, N, NDF or ADF disappearance after 48 h of incubation nor daily ammonia-N, volatile fatty acids or CH(4) production. However, enzyme application increased (P<0.05) microbial N production in feed particle-associated (loosely-associated) and silage feed particle-bound (firmly associated) fractions. With A. gayanus silage diets, degradation may not be limited by microbial colonization, but rather by the ability of fibrolytic enzymes to degrade plant cell walls within this recalcitrant forage.
authors.affiliation: 1Escola de Veterinária,Universidade Federal de Minas Gerais,Belo Horizonte,MG 31270-901,Brazil.
authors.forename: G O
authors.initials: GO
authors.lastname: Ribeiro
authors.affiliation: 1Escola de Veterinária,Universidade Federal de Minas Gerais,Belo Horizonte,MG 31270-901,Brazil.
authors.forename: L C
authors.initials: LC
authors.lastname: Gonçalves
authors.affiliation: 2Embrapa Gado de Leite - CNPGL,Juiz de Fora,MG 36038-330,Brazil.
authors.forename: L G R
authors.initials: LG
authors.lastname: Pereira
authors.affiliation: 3Faculty of Veterinary Science,University of Sydney,Sydney,NSW 2006,Australia.
authors.forename: A V
authors.initials: AV
authors.lastname: Chaves
authors.affiliation: 4Lethbridge Research Centre,Agriculture and Agri-Food Canada,Lethbridge,Alberta T1J 4B1,Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: 4Lethbridge Research Centre,Agriculture and Agri-Food Canada,Lethbridge,Alberta T1J 4B1,Canada.
authors.forename: K A
authors.initials: KA
authors.lastname: Beauchemin
authors.affiliation: 4Lethbridge Research Centre,Agriculture and Agri-Food Canada,Lethbridge,Alberta T1J 4B1,Canada.
authors.forename: T A
authors.initials: TA
authors.lastname: McAllister
mesh_terms: D000641:Ammonia / Q000378:metabolism; D031722:Andropogon / Q000378:metabolism*; D000818:Animals; D061249:Batch Cell Culture Techniques / Q000379:methods*; D002480:Cellulase / Q000494:pharmacology*; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation / Q000187:drug effects*; D008697:Methane / Q000096:biosynthesis; D012417:Rumen / Q000378:metabolism*; D012820:Silage / Q000032:analysis*; D014995:Xylosidases / Q000494:pharmacology*
chemical_list: D005232:Fatty Acids, Volatile; D000641:Ammonia; D014995:Xylosidases; D002480:Cellulase; D008697:Methane
keywords: Andropogon gayanus; Rusitec; exogenous fibrolytic enzyme; rumen microbial growth; tropical grass silage