Effects Of Lignocellulolytic Enzymes On Rumen Fermentation And Nutrient Digestibility In Holstein Bulls

The study investigated the effects of Lignocellulolytic enzymes(LE)on performance,rumen fermentation and nutrient digestion in bulls.Two experiment of repeated 4 × 4 Latin square designs were conducted.Four ruminal cannulaed Holstein bulls were used for each experiment.Laccase at the level of 0,0.2,0.4 and 0.6 g/kg dietary dry matter(DM)were supplemented to the basal diets in the first study.Four bulls consumed diets supplemented with LE at the level of 0,0.25,0.5 and 0.75 g/kg DM,respectively.Dry matter intake(DMI)and average daily gain(ADG)increased quadratically but feed conversion ratio(FCR)decreased linearly with increasing laccase addition.Increasing the level of laccase addition linearly increased digestibility of organic matter(OM),DM,crude protein(CP)and neutral detergent fibre(NDF)and quadratically increased acid detergent fibre(ADF).Digestible nitrogen(DN)elevated linearly and nitrogen retained(RN)and the ratio of RN to DN increased quadratically with increasing laccase supplementation.Ruminal p H quadratically decreased and total volatile fatty acids(TVFA)content quadratically increased.Acetate molar percentage,acetate to propionate ratio and ruminal ammonia-N(NH3-N)concentration reduced linearly but urinary total purine derivatives(TPD)excretion increased linearly.Effective degradability(ED)of CP in concentrate increased linearly and ED of DM,OM and NDF in corn silage increased quadratically with increasing laccase supplementation.Increasing laccase addition linearly increased activities of α-amylase and laccase and populations of Ruminococcus albus,Fibrobacter succinogenes,Butyrivibrio fibrisolvens and Ruminobacter amylophilus,and quadratically increased activities of cellobiase and populations of fungi,R.flavefaciens and P.ruminicola.Blood total protein(TP),albumin(ALB),insulin(INS)and total antioxigenic capacity(T-AOC)decreased quadratically but growth hormone(GH)and insulin-like growth factor-1(IGF-1)increased linearly with increasing laccase supplementation.Increasing the addition level of LE linearly increased DMI,ADG,nitrogen intake(IN)and digestibility of DM,OM,CP,EE,NDF and ADF in bulls.Rumen TVFA concentration linearly increased but ruminal p H,acetate molar percentage and acetate to propionate ratio linearly decreased with increasing LE addition.The ED of OM in concentrate and NDF in corn silage increased linearly.Increasing LE supplementation linearly increased activities of cellobiase and carboxymethyl-cellulase and populations of total bacteria,R.albus,F.succinogenes,B.fibrisolvens and P.ruminicola,and quadratically increased populations of fungi and Rb.amylophilus.Blood GLU,TP,total cholesterol(TC),GH and IGF-1 increased linearly with increasing LE supplementation.The results indicated that dietary laccase or LE supplementation improved growth performance,rumen fermentation and nutrient digestition in bulls,and the appropriate addition level of laccase and LE was 0.4 and 0.5 g/kg DM,respectively.