| The present work was conducted to assess nutritional values, heavy metals and fluorin contents of water hyacinth (WH), to study the suitable ensiling techniques of WH by addition of rice straw or wheat bran as absorbant or silage additives, and to evaluate the fermentation characteristics and organic matter digestibility (OMD) of the mixture of WH stem plus leaf meal with corn silage, Chinese ryegrass and alfalfa in vitro.Experiment 1. An investigation was conducted to determine the dry weight ratio, chemical compositions of fresh and dry root and stem plus leaf of WH that harvested in sewage. Both dry weights of root and stem plus leaf were less than 10% of fresh basis. Crude protein was about 10% of dry matter (DM) in both root and stem plus leaf of WH. Water soluble carbohydrates content was very low, especially in the root of WH. The neutral detergent fiber, acid detergent fiber and crude ash in root were 21.6, 56.3 and 16.4%DM higher than stem plus leaf, respectively. Except the chrome ion, other heavy metals and fluorin contents were one to three times in root higher than in stem plus leaf. The contents of cadmium, plumbum, chrome, arsenic and fluorin contents were under the Chinese Feed Hygeian Standard (GB13078-2001). It is indicated that WH was a kind of feedstuff with high neutral detergent fiber and high moisture content. It is safe to animals when WH grow in less-pollutant area.Experiment 2. This experiment was divided into three trials. First trial was conducted to investigate the quality of (WH) silage prepared with or without wheat bran (WB) or/and rice straw (RS). The WH silages were prepared in experimental glass containers to create four treatments: (1) 100% (fresh basis) WH (control); (2) 90% WH + 10% WB (WB10); (3) 90% WH + 10% RS, and (4) 90% WH + 5% WB + 5% RS (WB5RS5). The WH silage alone was of poor quality with undesirable odor and color. Addition of 10% WB increased the content of DM, crude protein and lactate, and lowered pH value, percentage of ammonia nitrogen in total nitrogen and butyrate content of silage (P<0.05). Addition with 10% RS increased DM content, and reduced proportion of ammonia nitrogen of total nitrogen and pH value as well as crude protein content (P<0.05), but had little effect on lactate content (P>0.05). In vitro gas production, rate of gas production, OMD and rumen volatile fatty acids contents in WB10 were increased significantly (P<0.05), but addition of 10% RS did not improve the in vitro rumen fermentation characteristics. Addition of 5% rice straw and 5% wheat bran resulted in intermediate quality silage between the WB10 and RS10 silages. It may be concluded that ensilaging of water hyacinth with 10% WB was an efficient way to improve the silage quality.From the above trial, it is indicated the pH value was not low enough and the OMD was not very high even in the WH silage mixed with 10% wheat bran. Therefore, a two-way factorial trail was then designed to study the effects of addition of lactobacillus and cellulase on fermentation characteristics of WH stem plus leafsilage. Lactobacillus was added at levels of 0 (L1), 10~6 (L2) and 10~8 CFU/kg (freshbasis) (L3), and cellulase was added at 0 (C1), 3000 (C2) and 6000 IU/kgDM (C3), respectively. Content of neutral detergent fiber was decreased significantly with increased levels of lactobacillus and cellulose, and was 3.9-5.7%DM and 2.7-3.4%DM lower in the treatment with lactobacillus and cellulase, compared with control. Ratio of ammonia nitrogen to total nitrogen in lactobacillus-added silage was 26.7-35.8% less than non-lactobacillus (P<0.05). The percentage of ammonia nitrogen was reduced significantly at 6000 IU/kgDM cellulase-added silage (P<0.05). Addition of lactobacillus and cellulase had interactive effects on the pH value, lactate and butyrate content of silage (P<0.05). There was a reverse change tendency in lactate and butyrate content as the added levels increased, and the pH value of WH stem plus leaf silage was lowest and lactate content was highest when the two additives were supplemented with the greatest doses.Finally, the pH value, lactic acid, water soluble carbohydrate, ammonia nitrogen and cellulose contents were determined for WH silage prepared under the suitable adding doses of lactobacillus and cellulase at day 1, 3, 5, 15, 25, 35 after ensilaging. The pH value decreased from 5.5 before ensiling to 4.3 on the 35th ensiling day, whereas the reverse change tendence was observed for lactic acid content. The cellulose content of silage was lower from 26.5%DM in raw material to 22.3%DM. The water soluble carbohydrate content was reduced during the whole ensiling period, but was not decreased significantly from the 5th to 15th day. The ammonia nitrogen content was increased from 4.61 to 8.25% of total nitrogen from the first 5 days at fast speed. It is indicated that lactobacillus and cellulase could greatly improve the quality of WH stem plus leaf silage.Experiment 3. The syringe gas test system was used to investigate fermented characteristics and OMD of the mixtures of WH stem plus leaf meal with corn silage, Chinese ryegrass and alfalfa at different levels (100, 67, 33 and 0% of WH) in vitro. As the WH stem plus leaf levels decreased, the potential gas production, gas production at 24h, rate of gas production and OMD appeared increasing tendence in corn silage group, but did not differ significantly from the 100% WH stem plus leaf (P>0.05). The reverse change occurred in the Chinese ryegrass group. With alfalfa mixture, when the WH stem plus leaf proportion decreased, the gas production rate and OMD increased significantly (P<0.05); Gas production and OMD increased by three times and 7%, respectively, when the ratio of WH stem plus leaf to alfalfa was at 33 to 67.In summary, the WH is a kind of roughage with medium protein, high fiber, high moisture and low digestibility. Addition of wheat bran may improve the fermentation quality of WH silage, while addition with lactobacillus and cellulase may greatly improve the WH silage. The WH stem plus leaf maybe included in animal diet in combination with other feeds such as alfalfa. |
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