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The objective of this study was to investigate the effects of different dose of chitosan orchitosan added to mixtures differing in forage-to-concentrate ratios on rumen methaneproduction and fermentation characteristics using the rumen simulation technique (Rusitec).There are two experiments.Experiment one: Effects of chitosans on rumen methane production and fermentationcharacteristics. A completely randomized design was used. There were four groups andaddition of chitosan was0(Control),500,1000,1500mg. After seven days’ adptation, thefermentation parameters were determined for2days. Two continues periods’ experimentswere done. The ratio of forage to concentrate of the diet was60:40(Dry matter basis).Compared with the control group, the methane concentrations were decreased (P<0.001) by17.71,31.67,50.37%in24hours respectively at three chitosan adding group. Addingchitosan decreased acetic acid molar proportions (P<0.006), butyric acid molar proportions(P≤0.001) and acetic acid to acrylic acid ratio (P≤0.025), increased propionic acid molarproportions (P≤0.008). Ammonia nitrogen concentration, urea nitrogen concentration at0,3,6,9,12h (P≤0.008) and total nitrogen at0,3,9,12h (P<0.001) were lower whereas microbenitrogen at every sampling time (P≤0.009) was higher than that in the control group.Compared with the basal diet, the crude protein were decreased (P<0.001) by11.72,17.04%at1000mg,1500mg chitosan adding group. There was a significant linear patterns formethane, acetic acid, butyric acid, propionic acid, acetic acid to acrylic acid ratio, totalnitrogen, ammonia nitrogen, urea nitrogen, microbe nitrogen and crude protein digestibilitywith the increasing chitosan dose (P≤0.016). The pH of rumen fluid, total gas production,branch fatty acid, the digestibility of neutral detergent fiber were no significant difference atevery groups (P>0.05).Experiment two: Effects of chitosan added to mixtures differing in forage-to-concentrateratios on rumen methane production and fermentation characteristics. A2×2experimentaldesign (4groups) was used. The two factors were forage-to-concentrate ratio and differentdoses of chitosan. The forage-to-concentrate ratios were30:70and70:30. The differentdoses of chitosan were0and1500mg. Four Rusitec vessels received30:70diet and theothers received70:30diets. Two of30:70diet vessels received0or1500mg chitosans. Sodid the70:30diets vessels. Two continues periods’ experiments were done. Compared withthe low-concentrate diet, high-concentrate diet decreased rumen methane concentrations(P<0.001) acetic acid molar proportions (P≤0.001), butyric acid molar proportions (P<0.001), acetic acid to acrylic acid ratio (P<0.001), ammonia nitrogen (P<0.001), NDF (P<0.001),crude protein digestibility (P<0.001) and increased gas production (P<0.001) and propionicacid (P<0.001). low-concentrate diet increased pH of rumen fluid (P=0.046) at6h. Adding1500mg chitosan decreased methane (P<0.001), gas production (P<0.001), acetic acid molarproportions (P<0.001), butyric acid molar proportions (P<0.001), acetic acid to acrylic acidratio (P<0.001), ammonia nitrogen (P<0.001), crude protein digestibility (P<0.001) andincreased the propionic acid (P<0.001). There was a significant interaction (P≤0.026)between forage ratio and chitosan based on methane, gas production, ammonia nitrogen at0,6h and crude protein digestibility. The rate of the reduction of methane and ammonia nitrogenat0,6h in high concentrate diet was higher than that in low-concentrate diet by addingchitosan. The rate of the reduction of crude protein digestibility and the level of increase ofgas production in high concentrate diet was lower than that in low-concentrate diet by addingchitosan.These results showed that:(1), The chitosan could reduce rumen methane production,change the type of fermentation, increase acrylic acid ratio, decrease the yield of acetic acidand improve the energy utilization to alleviate the environmental pollution of methane andprotect the protein in the feed from the rumen microbial degradation.(2), Compared with thelow-concentrate diet, high-concentrate diet decreased the rumen methane, acetic acid,ammonia nitrogen, crude protein and neutral detergent fiber digestibility and increased totalgas production and acrylic acid.(3), The effectsof chitosan on rumen methane production andfermentation were related to the forage-to-concentrate ratio. The rate of the reduction ofmethane, gas production and ammonia nitrogen in high concentrate diet was higher than inlow-concentrate diet by adding chitosan and the rate of the reduction of crude protein andneutral detergent fiber digestibility Chitosan added to the high concentrate diet better thanlow-concentrate diet. The effects of chitosan adding to high-concentrate diet were better thanthat adding to the low-concentrate diet.
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