| Methane emission from ruminant livestock represents a loss of dietary energy, and alsois a greenhouse gas, which may exacerbate globle warming. There are many strategies try toreduce methane production from ruminants, although some methods have been successful,the use of some compounds was limited due to human health concerns or the depression offibre degradation. It is necessary to find a way for reducing methane production withoutdepressing fibre degradation. This experiment was conducted to evaluate the effects ofchitosan and exogenous fibrolytic enzyme on ruminal fermentation and microbial populations,to explore chitosan and fibrolytic enzyme was used in ruminant diets, and to improve the feedutilization on ruminant. The results of the present experiments will also provide theoreticalbasis scientific evidence for application of chitosan and fibrolytic enzyme in practice.Trial1Effects of chitosan on in vitro ruminal fermentation in diets with different forageto concentrate ratiosThis study was conducted to investigate the effects of chitosan on ruminal fermentation,methane production and microbial populations in diets with different forage to concentrate(F:C) ratios in vitro. A two factorial in vitro experiment was designed with one factor as threeF:C ratios (80:20,50:50and20:80) diets and the other as four levels of chitosan inrumen-buffer fluid (0,40,80and120g DM substrate). After24h incubation, the resultsshowed that chitosan significantly decreased in vitro dry matter disappearance (IVDMD)(P<0.05), total gas production (P<0.05), methane production (P<0.05) and acetate:propionate (A:P)(P<0.05), and significantly increased the rumen pH (P<0.05). Chitosansignificantly increased the molar proportion of propionate of rumen-buffer fluid in F:C ratiosof80:20and50:50(P<0.05). In F:C ratios of20:80, Chitosan significantly increased theammonia-N concentration (P<0.05) and the molar proportion of butyrate, Valerate andBCVFA (P<0.05) and significantly decreased the molar proportion of acetate (P<0.05).Chitosan increased the number of F. succinogenes (P<0.05), but had no significant effects onthe number of total bacteria, protozoa and anaerobic fungi. In conclusion, chitosan affected the ruminal fermentation and reduced methane production of rumen-buffer fluid in vitro.Trial2Effects of exogenous fibrolytic enzyme on in vitro ruminal fermentation andmicrobial populations of substrates with different forage to concentrate ratiosThis research was conducted to investigate the effects of exogenous fibrolytic enzymeon in vitro ruminal fermentation and microbial populations with substrates in different forageto concentrate ratios (F:C). Four levels (0,40,80and120U/g DM substrate) of fibrolyticenzyme were supplemented to buffered rumen fluid and incubated with three different F:Cratios (80:20,50:50and20:80) substrates at39C. After24h incubation, the results showedthat in three different F:C ratios, fibrolytic enzyme significantly increased (P<0.05) total gasproduction, IVDMD, concentration of total volatile fatty acid and molar proportion ofpropionate, and decreased (P<0.05) pH, but it did not significantly affect (P>0.05) molarproportion of butyrate. And in the high (F:C80:20) and medium (F:C50:50) foragesubstrates, fibrolytic enzyme increased (P<0.05) the molar proportion of propionate anddecreased (P<0.05) the ratio of acetate to propionate, but the effects did not observed in highconcentrate (F:C20:80) substrates. It was also found that fibrolytic enzyme increased(P<0.05) the number of F. succinogenes and methanogens in the F:C80:20substrate, butthere was no significant (P>0.05) effects on microbial populations in the F:C50:50and20:80substrates. The results indicated that the fibrolytic enzyme improved the degradation ofsubstrates, and had different effects on the ruminal fermentation pattern and microbialpopulations under three F:C ratio substrates. The efficiency of fibrolytic enzyme on high andmedium forage substrates was greater than low forage substrates.Trial3Effects of hemicellulase on ruminal fermentation and microbial populations ofsubstrates with different forage to concentrate ratiosThe effects of hemicellulase on IVDMD and ruminal fermentation in diets of threeforage to concentrate ratios were evaluated in in vitro batch cultures. The experiment had a3×4factorial design with three different F:C ratio diets and four levels of hemicellulase:0,40U,80U and120U/g DM substrates. After24h incubation, Samples were collected todetermine rumen fluid pH, volatile fatty acids (VFA), ammonia-N concentration andmicrobial populations. The hemicellulase increased (P<0.05) the IVDMD and the productionof gas, methane and total VFA. Hemicellulase did not affect acetate, butyrate and valeratemolar proportions, but decreased (P<0.05) branch-chained volatile fatty acids molarproportion and A:P, and increased propionate molar proportion. Hemicellulase increased(P<0.05) the number of methanogenes, but decreased (P<0.05) the number of protozoa, anddid not affect the number of total bacterial, F. succinogenes and anaerobic fungi. These resultsindicated that hemicellulase improve degradability of DM, and influence ruminal fermentation and the effects dependent the nature of the incubated substrate.Trial4Effects of chitosan and exogenous fibrolytic enzyme on in vitro ruminalfermentation and microbial populations of substrates with different forage toconcentrate ratiosThis research was conducted to investigate the effects of exogenous fibrolytic enzyme,chitosan and Mixture (containing of exogenous fibrolytic enzyme and chitosan) on in vitrofermentation of substrates with three different forage to concentrate ratios. Exogenousfibrolytic enzyme (80U/g DM substrate), chitosan (80mg/g DM substrate) and Mixture(fibrolytic enzyme80U/g+chitosan80mg/g DM substrate) was added to substrates withthree different Forage to concentrate ratios, and incubated for24h in a39℃incubator shaker.After24h incubation, exogenous fibrolytic enzyme and Mixture increased (P<0.05) total gasproduction, IVDMD and the total volatile fatty acid (VFA) production. Compared tofibrolytic enzyme, Mixture treatment decreased (P<0.05) methane production, CH4/VFA andA:P ratio. Chitosan treatment decreased (P<0.05) the IVDMD, methane emission, total VFAproduction and A:P contrast to control treatment. Compared to chitosan treatment, Mixturetreatment increased (P<0.05) IVDMD and total VFA production, and the methane productionno significantly effects. Among the three additives and control (no added additives), theMixture has a lower CH4/VFA and the lowest A:P ratio than other treatments. The MIXtreatment significantly increased (P<0.05) the number of F. succinogenes. The results of thisresearch indicated that the Mixture would be benefited the ruminal fermentation, especiallyon IVDMD and CH4/VFA and the effects of Mixture on ruminal fermentation depend on thedifferent F:C ratios substrates.In conclusion, addition of chitosan reduce the production of methane, exerte an effect onsome fermentative processes in the rumen, modulate the ruminal fermentation; Exogenousfibrolytic enzyme preparations may be useful dietary supplements for improving fiberdigestion in the rumen; The combined application of chitosan and fibrolytic enzyme, reducethe production of methane without reducing the digestibility of DM, benefit to the rumenfermentation, which may improve the energy efficiency. |
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