Selective ligninolysis of wheat straw and wood chips by the white-rot fungus Lentinula edodes and its influence on in vitro rumen degradability

Background： The present work investigated the influence of lignin content and composition in the fungal treatment of lignocellulosic biomass in order to improve rumen degradability. Wheat straw and wood chips,differing in lignin composition, were treated with Lentinula edodes for 0, 2, 4, 8 and 12 wk and the changes occurring during fungal degradation were analyzed using pyrolysis-gas chromatography-mass spectrometry and detergent fiber analysis.Results： L. edodes preferentially degraded lignin, with only limited cellulose degradation, in wheat straw and wood chips, leaving a substrate enriched in cellulose. Syringyl（S）-lignin units were preferentially degraded than guaiacyl（G）-lignin units, resulting in a decreased S/G ratio. A decreasing S/G ratio（wheat straw： r =-0.72, wood chips： r =-0.75） and selective lignin degradation（wheat straw： r =-0.69, wood chips： r =-0.88） were correlated with in vitro gas production（IVGP）, a good indicator for rumen degradability.Conclusions： L. edodes treatment increased the IVGP of wheat straw and wood chips. Effects on IVGP were similar for wheat straw and wood chips indicating that lignin content and 3D-structure of cell walls influence in vitro rumen degradability more than lignin composition.

Physical and chemical changes of rapeseed meal proteins during toasting and their effects on in vitro digestibility

Background： Toasting during the production of rapeseed meal（RSM） decreases ileal crude protein（CP） and amino acid（AA） digestibility. The mechanisms that determine the decrease in digestibility have not been fully elucidated. A high protein quality, low-denatured, RSM was produced and toasted up to 120 min, with samples taken every 20 min. The aim of this study was to characterize secondary structure and chemical changes of proteins and glucosinolates occurring during toasting of RSM and the effects on its in vitro CP digestibility.Results： The decrease in protein solubility and the increase of intermolecular β-sheets with increasing toasting time were indications of protein aggregation. The contents of NDF and ADIN increased with increasing toasting time.Contents of arginine, lysine and O-methylisourea reactive lysine（OMIU-RL） linearly decreased with increasing toasting time, with a larger decrease of OMIU-RL than lysine. First-order reactions calculated from the measured parameters show that glucosinolates were degraded faster than lysine, OMIU-RL and arginine and that physical changes to proteins seem to occur before chemical changes during toasting. Despite the drastic physical and chemical changes noticed on the proteins, the coefficient of in vitro CP digestibility ranged from 0.776 to 0.750 and there were no effects on the extent of protein hydrolysis after 120 min. In contrast, the rate of protein hydrolysis linearly decreased with increasing toasting time, which was largely correlated to the decrease in protein solubility, lysine and OMIU-RL observed. Rate of protein hydrolysis was more than 2-fold higher for the untoasted RSM compared to the 120 min toasted material.Conclusions： Increasing the toasting time for the production of RSM causes physical and chemical changes to the proteins that decrease the rate of protein hydrolysis. The observed decrease in the rate of protein hydrolysis could impact protein digestion and utilization.

Sainfoin(Onobrychis viciifolia)silage in dairy cow rations reduces ruminal biohydrogenation and increases transfer efficiencies of unsaturated fatty acids from feed to milk

The effects of replacing grass silage by sainfoin silage in a total mixed ration(TMR)based diet on fatty acid(FA)reticular inflow and milk FA profile of dairy cows was investigated.The experiment followed a crossover design with 2 dietary treatments.The control diet consisted of grass silage,corn silage,concentrate and linseed.In the sainfoin diet,half of the grass silage was replaced by a sainfoin silage.Six rumen cannulated lactating multiparous dairy cows with a metabolic body weight of 132.5±3.6 kg BW^0.75,214±72 d in milk and an average milk production of 23.1±2.8 kg/d were used in the experiment.Cows were paired based on parity and milk production.Within pairs,cows were randomly assigned to either the control diet or the sainfoin diet for 2 experimental periods(29 d per period).In each period,the first 21 d,cows were housed individually in tie-stalls for adaptation,then next 4 d cows were housed individually in climate-controlled respiration chambers to measure CH4.During the last 4 d,cows were housed individually in tie stalls to measure milk FA profile and determine FA reticular inflow using the reticular sampling technique with Cr-ethylenediaminetetraacetic acid disodium salt dihydrate(EDTA)and Yb-acetate used as digesta flow markers.Although the dietary C18:3n-3 intake was lower(P=0.025)in the sainfoin diet group,the mono-unsaturated FA reticular inflow was greater(P=0.042)in cows fed the sainfoin diet.The reticular inflow of trans-9,trans-12-C18:2 and cis-12,trans-10 C18:2 was greater(P≤0.024)in the sainfoin diet group.The cows fed sainfoin diet had a lower(P≤0.038)apparent ruminal biohydrogenation of cis-9-C18:1 and C18:3n-3,compared to the cows fed the control diet.The sainfoin diet group had greater(P≤0.018)C18:3n-3 and cis-9,cis-12-C18:2 proportions in the milk FA profile compared to the control diet group.Transfer efficiencies from feed to milk of C18:2,C18:3n-3 and unsaturated FA were greater(P≤0.0179)for the sainfoin diet.Based on the results,it could be concluded that replacing grass silage by sainfoin silage in dairy cow rations reduces ruminal C18:3n-3 biohydrogenation and improves milk FA profile.