The Effects Of Xylanase And Cellulose On Growth Performance, Nutrition Digestibility, Ruminal Fermentation And Microbial Diversity In Heifers

Strains in soil which can produce xylanase were screened from soil. And a strain producing xylanase with highest activity was selected and identified as Aspergillus Niger. This xylanase was studied with its characters such as optimized pH, temperature, and thermal stability. Then it was mixed with cellulose, amylase and protease in different rates to be compound enzymes. Their abilities to degrade corns, bean, and green dry grasses in vitro were detected and the best ratios was determined. Synergetic effect between external enzymes and internal enzymes in rumen was studied in order to understand the mechanism of the higher use of feed when adding external enzymes. More researches were done to know the effects of external compound enzymes influenced in rumor. Experiments of the growth, digestion, and metabolism of replacement cattle aged from three months to seven months were carried out to analyze effects that external enzymes influenced the growing performance, digestion, indexes in blood, fermentation in rumor and changes of micro-organisms in rumor. The article explained the use of external enzymes and their mechanism of action in ruminants.1. Screen acidic xylanase-producing microbes from natural environment for potential use in feed industry. Twenty xylanase-producing strains were isolated from soil by enrichment culture techniques. Five strains were chosen to ferment in shaking flasks. The strain S8-3, which had the highest production of xylanase, was preliminarily identified by standard methods, and the property of the xylanase produced by the strain was studied. Strain S8-3 was identified as Aspergillus Niger. The maximal enzymatic activity of xylanase in culture liquid was 628.43 U/mL. The xylanase activity was optimal at 45 degrees C and pH 4.5. Xylanase was stable at pH ranging from 3.0 to 7.0. Xylanase retained more than 60 % of its original activity after incubation for 30 min at 70 degrees C. The xylanase produced by strain S8-3 in this study may have the potential in feed industry.2. An in vitro system was conducted to investigate the effects of eight different levels of exogenous complex enzymes in a corn-soybean meal-hay diet on rumen fermentation. Exogenous complex enzyme consisted of cellulose, xylanase, acid protease, neutral protease and pectinase. The results showed gas production, ammonia-N (NH3-N), volatile fatty acids (VFA) concentration in each treatment were significantly higher than those in Control treatment (P<0.05). It also showed that the rumen fermentation pattern was changed with the addition of exogenous complex enzyme, and gas production in vitro, NH3-N and VFA concentration and the degradability were improved. Under the conditions of this experiment, high cellulose, low xylanase pattern group had better degradation on the corn - soybean meal - hay substrate; acid protease, neutral protease, pectinase had no significant effects on the degradation.3. The mechanism by which enzyme additives improve feed digestion in ruminants is not fully understood. Direct hydrolysis of feed in the rumen is a potential mode of action, but the importance of this mode needs to be quantified because of the relatively low exogenous hydrolyses activity added compared with the total activity added compared with the total activity present in the rumen. We examined the interactions between ruminal and exogenous enzymes on substrate (CMC, xylan and TMR) degradation using a completely randomized experimental design, with a 6(enzyme preparations and their combinations)×5(assay pH) arrangement of treatments. Ruminal enzymes were extracted from cattle fitted with rumen cannulae. Exogenous enzymes were commercial enzyme include cellulose and xylanase. The complex enzymes A, which was composed with the xylanase, cellulose and ruminal enzymes at the ratio of one third each. The complex enzymes B, which was composed with the xylanase and ruminal enzymes at the ratio of 0.5 to 0.5. The complex enzymes C, which was composed with the cellulose and ruminal enzymes at the ratio of 0.5 to 0.5. Ruminal and exogenous enzymes preparations and their combinations were tested for the ability to degrade soluble cellulose, xylan, and TMR over a range of pH form 4.5 to 7.0 at 39℃. Exogenous enzymes acted synergistically with enzymes from mixed rumen microorganisms in degrading soluble cellulose, xylan and TMR. The exogenous enzymes can interact with the ruminal enzymes when depredating CMC, Xyaln and TMR under the conditions of pH4.5-7.0, 39℃. Then the hydrolysis products of TMR were detected. The concentrate of glucose and xylan of the complex A group were 86 percent and 112 percent higher than ruminal enzymes group; the concentrate of xylan of the complex B group were 217 percent higher than ruminal enzymes group, but of the glucose was no different; The concentrate of glucose and xylan of the complex C group were 43 percent and 94 percent higher than ruminal enzymes group. And hydrolysis ability was much higher under pH 6.0-6.5, 39℃conditions. The synergistic effect between ruminal and exogenous enzymes increased the hydrolytic potential within the rumen environment and is likely a significant mechanism by which enzyme additives improve feed digestion.4. The effect of supplementation of exogenous enzymes on growth performance, nutrition digestibility and metabolism, rumen fermentation and microbiota diversity of 3 to 7 month heifers was studied. 16 herds heifer were selected on 3 month old, 4month old, 5 month old, respectively, add up to 48 herbs. The age of heifers in 3 month were randomly divided into two groups, labeled CT, ET; aged at 4 month heifers were randomly divided into two age groups, labeled CA, EA; aged at 5 month heifers were randomly divided into 2 groups were labeled as CM, EM. CT, CA, CM group of heifers fed control group TMR, ET, EA, EM group cows fed TMR supplement enzyme in a dose of 20g / day. head. The results showed that between ET and CT groups, between EA and CA groups, between EM and CM groups, body weight gain and average daily gain were significantly different. Adding enzyme can promote the growth of bovine abdomen and chest. Rumen fermentation parameters of each group heifers were measured. The results show that compound enzyme can increase the total rumen volatile fatty acids and acetic acid content, as well as acetic acid / propionic acid ratio. Digestion experiment results showed that compound enzyme preparations can increase the NDF, ADF apparent digestibility, total energy apparent digestibility, but crude fatty and crude protein digestibility did not significantly affected by compound enzyme treatment. The analysis results showed that plasma triglycerides, cholesterol, ALP levels were not significantly different. It could conclusion that TMR of exogenous enzymes can improve the feed digestion and promote the development of the rumen, improve ruminal fermentation, have no effects on lipid metabolism and protein metabolism, and thus promote their growth on 3 to 7 months heifers.5. Using sequence analysis of DGGE combined PCR to evaluate the microbiota diversity of heifers feed TMR treated by compound enzyme. The results showed that all groups of bacteria DGGE profiles reserve rumen similarity is not high, but enzyme preparation treatments increased numbers of DGGE bands, the results show that the rumen microbiota diversity changed. Sequence analysis showed that there were 2 clones, respectively Prevotella sp. and Ruminococcus flavaciens similarity higher than 96% in enzyme treatment group. Enzyme treatment can promote the establishing of advantages of ruminal microflora.