Cellulase is a general term for a multi-component enzyme system that hydrolyzes cellulose into glucose, also known as cellulase. Synergism occurs between the enzyme systems, which break down cellulose to produce oligosaccharides and cellobiose, which are ultimately hydrolyzed to glucose. However, in the current shortage of resources in the feed industry, on the one hand, the most abundant renewable resources on the planet - cellulose is not fully utilized, on the other hand, the lack of endogenous enzymes in ruminants reduces the digestibility and utilization of feed. rate. Therefore, cellulase as a high activity biocatalyst has broad application prospects in ruminant feed production. This article only briefly describes the mechanism of action of cellulase and its application in ruminant feed.
1 Mechanism of action of cellulase
1.1 Improve the digestion and absorption of nutrients
In addition to cellulolytic and hemicellulose, cellulase can also promote the dissolution of plant cell walls, dissolve more plant cell contents, and degrade non-digestible macromolecular polysaccharides, proteins and lipids into Small molecular substances are beneficial to the digestion and absorption of the gastrointestinal tract of animals.
1.2 Supplementation of insufficient endogenous enzymes
Cellulase can activate the secretion of endogenous enzymes, supplement the deficiency of endogenous enzymes, and adjust the endogenous enzymes to ensure the normal digestion and absorption functions of animals, and play a role in disease prevention and growth promotion.
1.3 Eliminate the effects of anti-nutritional factors
When hemicellulose and pectin are partially dissolved in water, they will produce a viscous solution, which will increase the viscosity of the digested material and cause obstacles to endogenous enzymes. Adding cellulase can reduce the viscosity and increase the diffusion of endogenous enzymes. The contact area between the enzyme and nutrients promotes digestion of the feed and promotes healthy growth of the animal.
1.4 Synergism of cellulase system
A cellulase preparation is a multi-enzyme complex composed of a protease, an amylase, a pectinase, and a cellulase. In this multi-enzyme complex system, an enzyme product can be the base of another enzyme. The substance, so that the digestion in the digestive tract can proceed smoothly. That is to say, in addition to directly degrading cellulose and promoting its decomposition into low molecular compounds which are easily digested and absorbed by animals, cellulase also works together with other enzymes to improve the decomposition and digestion of feed nutrients in dairy cows.
2 application effect of cellulase in ruminant feed
2.1 Improve the quality of silage
Silage is a process in which a fermented substrate (soluble sugar) in a raw material is converted into an acid substance such as lactic acid by the proliferation of a beneficial microorganism to create an acidic environment and inhibit the proliferation of harmful microorganisms, thereby preserving the nutrient component of the raw material. Studies have shown that the addition of cellulase preparation during silage, the decomposition of plant cell wall by cellulase, promote lactic acid fermentation, reduce the content of neutral detergent fiber and acid detergent fiber in silage, and improve the digestibility of silage.
Sun Juanjuan et al. (2007) reported that cellulase significantly reduced the pH of Leymus chinensis silage and increased lactic acid content (P<0.05). Chen Yuying et al. (2007) added a composite of green juice fermentation broth and cellulase in grassy silage, which can reduce the pH and ammonia nitrogen of silage, improve the recovery of dry matter and crude protein content, and improve the quality of silage. Xue Yanlin et al. (2007) showed that the addition of cellulase to wheat straw yellow storage can significantly reduce the pH, ammonia nitrogen, neutral detergent fiber and acid detergent fiber content of wheat straw silage (P<0.05). At the same time, the content of lactic acid, total acid and crude protein were significantly increased (P<0.05).
Sheperd et al. (1995) added cellulase and lactic acid bacteria to silage alfalfa. The results showed that the content of neutral detergent fiber and acid detergent fiber was significantly lower (P<0.05), and the pH was also significantly lowered (P<0.05). ), and after the fermentation is completed, since the enzymatic hydrolysis is still ongoing, the sugar content continues to increase.
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2.2 Increase daily gain and improve feed digestibility
Adding cellulase to the diet can increase the digestibility and utilization of the feed and increase the absorption of nutrients by the animal. Deng Yuying et al (2010) reported that 0.5% cellulase was added to the diet of weaned lambs. Compared with the control group, the average daily weight gain of the test sheep increased by 4.22% (P>0.05), the feed-to-weight ratio decreased by 5.20%, and diarrhea. The rate is also significantly reduced. Wang Ping (2008) reported that the addition of cellulose complex enzyme had a significant effect on the growth of fattening sheep, which could increase the daily gain by 43.98% (P<0.01) and reduce the feed-to-weight ratio by 30.55% (P<0.01). Yan Hongwei et al. (2000) showed that the addition of 0.2% composite cellulase to the basal diet had the best daily gain effect. The reason may be that it properly supplements the deficiency of endogenous enzymes in the rumen of cattle, thereby improving the digestive tract environment and animal physiology, improving the digestion and absorption of crude fiber and other nutrients, and promoting the better growth and development of the carcass. . Similar reports have been made by Knownlton et al. (2002). Li Xiaodong et al. (2007) found that low protein diet supplemented with 0.2% composite cellulase had a tendency to increase crude fiber digestibility (P>0.05), while low dietary energy levels plus enzyme preparations could be significantly improved ( P < 0.05) digestibility of crude fat and absorption rate of calcium.
In addition, another method of adding cellulase is in vitro enzymatic hydrolysis, that is, after mixing cellulase with straw or other roughage, it is accumulated or sealed at a certain temperature, humidity and pH for a certain period of time, and then dried. Or feed the animals directly. Jin Jiaming et al. (2007) reported that the use of cellulase-encapsulated wheat straw to feed small-tailed Han sheep, the average daily gain of each test sheep was 148g, which was 68.2% higher than the control group (P<0.05); the profit was 56.1 yuan. It is 32.7 yuan higher than the control group and the economic benefit is increased by 139.7%. Jiang Guixia and Xue Bai (2007) used two methods to separately add 5g of cellulase preparation to the concentrate and spray it on wheat straw grass to study its application effect on yak. The results showed that both the experimental groups significantly increased the digestibility of dry matter and the average daily gain (P<0.05), which were 4.57%, 6.18%, 42.85% and 35.71% higher than the control group, respectively. The group difference was not significant (P>0.05). Zhang Sujiang et al. (2007) reported that the treatment of roughage with FE808 cellulose complex enzyme is beneficial to increase DM digestibility and utilization of CF, CP and Ash, and has better effects on camel thorn, alfalfa and salt-eared wood. Certain effect.
2.3 Increase the milk yield of ruminants and improve the quality of milk
Numerous studies have shown that the addition of cellulase to roughage, grain or concentrate can increase the milk yield of ruminants and improve milk quality. Wang Zhaozhong et al. (2007) added 1% cellulose complex enzyme to dairy cow diet. The average milk fat percentage of the experimental group was increased by 1.03 percentage points compared with the control group, an increase of 22.1% (P<0.01). Ma Shuangqing et al. (2008) showed that the composite cellulase preparation containing 1% of concentrate in dairy cow diet can significantly increase milk production (P<0.05); milk fat percentage increased slightly, but no obvious difference. Zhou Lifen et al. (2006) reported that different doses of cellulase preparations were added to Holstein dairy cow diets. The results showed that the average daily milk yield of the experimental group was increased by 1.05 kg (5.73%) and 0.88 kg (4.84%), respectively. 0.66kg (3.62%) and 0.51kg (2.81%), but the difference was not significant (P>0.05), and 50g/t of cellulase A had the best effect. Hu He et al (2001) added 0.1% cellulase-based compound enzyme to dairy cow diet. The milk yield of dairy cows increased by 2.5kg, 9.47% (P<0.05), and the milk fat percentage of the experimental group. The dry matter in milk protein, lactose and milk does not decrease with the increase of milk production, but slightly increases or remains unchanged, and the economic benefit is significantly improved. Liu Jianchang et al. (2001) added 0.1% cellulase preparation to the concentrate of Holstein cows. After 60 days of testing, it was found that the average daily milk yield of the test cattle increased by 14.89% (P<0.05). The cattle earn more than 5.41 yuan per day. Yin Qingqiang et al. (1991) reported that after adding 50g/(head?d) cellulase to dairy cow diet, it could increase the milk yield by 8.30%, and the feed consumption per kilogram of milk yield decreased by 10.0%. The economic benefit was very obvious.
Zhu Guosheng and Li Zhongli (2002) used in vitro enzymatic hydrolysis method and used corn stalk silage made by adding cellulase. After feeding the goats, it was found that the milking rate of the experimental group was 6.9% higher than that of the control group, and the milk fat percentage was slightly increased (P >0.05).
2.4 Improve rumen fermentation function
There are few reports on the study of rumen fermentation function by cellulase. Jing Changwei et al (2006) added different doses of Chaetomium thermophila cellulase to the diet of small tailed Han sheep with permanent rumen fistula to study its effect on rumen fermentation function. The results showed that the changes of rumen acetic acid, propionic acid and total VFA in each group were basically the same, that is, gradually increased after feeding, in which the concentration of acetic acid and total VFA reached the highest point after 2h, and the concentration of propionic acid reached the highest point in 4h. Then, the steady drop was reduced to the lowest point before feeding, and this pattern was repeated after eating again. The acetic acid and total VFA yields in the 0.6% level group at 08:00, 09:00, 14:00, 17:00, 20:00, 21:00, and 23:00 were significantly or significantly higher than the control group ( P<0.05 or P<0.01); and 0.6% cellulase preparation significantly reduced rumen pH compared with the control group at 10:00 and 23:00 (P<0.05); Yin Qingqiang and Chen Shuxing (1998) It indicated that 30g/(d?) cellulase could significantly increase the activity of protease and CMC enzyme in rumen fluid of sheep and increase the yield of acetic acid, propionic acid and butyric acid (P>0.05).
3 Conclusion
At present, the research of cellulase has attracted extensive attention from academic circles at home and abroad, covering not only the feed industry, but also the food, textile, bioenergy development and other industries. Therefore, cellulase is a highly efficient and safe biocatalyst, and its application prospect is very broad. However, cellulase in the feed industry still has a series of problems such as low yield, high cost, easy inactivation, unclear addition and unclear addition. In the future, we must further study and explore the above issues, accelerate the production and promotion of cellulase, and ensure its application effect, thus promoting the healthy development of ruminant breeding industry. --Chinese cows
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