Pretreatment method for improving rumen degradation rate of straw feed

Abstract

The invention belongs to the field of agricultural waste resource utilization, and relates to a pretreatment method for improving the rumen degradation rate of straw feed. The pretreatment method comprises the step of performing liquid nitrogen freezing on the straw feed before the straw feed is fed. The liquid nitrogen pretreatment method has an obvious improvement effect on the fiber structure of the straw feed, the degradation rate of the straw feed in the rumen can be obviously increased, and digestion and utilization of the straw feed in the rumen of ruminants are promoted.

Description

Technical Field

[0001] The invention belongs to the field of agricultural waste resource utilization, and particularly relates to the application of low-temperature freezing technology in improving the degradation characteristics of straw feed. Background Art

[0002] As a major byproduct of crop production, straw is rich in cellulose, hemicellulose, and lignin. Currently, straw is utilized primarily as energy, material, fertilizer, and feed. Traditionally, straw feed is fed directly or after minimal processing to animals, resulting in low efficiency. Some straw utilization technologies are not yet mature, resulting in high costs.

[0003] Straw is a potential source of high-quality roughage for ruminants. However, straw's natural anti-degradation barrier results in a low rumen degradation rate, and the dry matter digestibility of untreated straw is generally low, severely limiting its efficient utilization in animal husbandry. To address the problem of low straw digestibility, physical, chemical, biological, and composite pretreatment technologies have been developed both domestically and internationally. Physical treatments, among them, change the physical structure of straw through mechanical action, including cutting and crushing, thermal spraying, steam explosion, and puffing. However, these physical treatments have limited effects on improving rumen degradation rates, and some physical treatment methods require high equipment investment and high energy consumption. Chemical treatments use acids, alkalis, and oxidants to destroy the structure of lignocellulose, including alkalinization, sodium hydroxide treatment, limewater treatment, and ammoniation treatment. These treatment methods are costly and may pollute the environment. Biological treatments use microorganisms or enzymes to decompose straw fibers, including silage and enzymatic hydrolysis, but have drawbacks such as slow speed and difficulty in controlling progress.

[0004] Pretreatment disrupts the lignin-hemicellulose crosslinks, exposing cellulose microfibrils and increasing the contact area with rumen microbes. Rumen microbes (such as Bacteroidetes and Firmicutes) secrete glycosidases and esterases, which convert cellulosic polysaccharides into volatile fatty acids (VFAs). Therefore, developing low-cost, environmentally friendly, and efficient straw pretreatment technologies, especially customized solutions tailored to specific straw types and animal needs, is key to improving straw feed utilization. Summary of the Invention

[0005] In order to overcome the above-mentioned defects, the purpose of the present invention is to provide an application of low-temperature freezing technology in improving the rumen degradation rate of straw feed. The low-temperature freezing pretreatment method of the present invention significantly improves the rumen dry matter degradation rate of straw feed after liquid nitrogen treatment.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0007] A pretreatment method for improving the rumen degradation rate of straw feed comprises: freezing the straw feed with liquid nitrogen before feeding the straw feed.

[0008] Furthermore, the straw feed includes one or more of rice straw, corn straw, wheat straw, and rape straw.

[0009] Furthermore, the improving the rumen degradation rate of straw feed includes improving the dry matter degradation rate of straw feed.

[0010] Furthermore, the improving the rumen degradation rate of straw feed includes improving the degradation efficiency of straw feed in the rumen of ruminants.

[0011] Furthermore, the method of improving the rumen degradation rate of straw feed includes changing the arrangement of straw feed fibers, loosening the fiber structure of straw feed, and promoting the fermentation of straw feed in rumen fluid.

[0012] Furthermore, the liquid nitrogen freezing time is 2 to 8 hours.

[0013] Furthermore, the liquid nitrogen freezing of the straw feed includes completely immersing the straw feed cut into sections of 2 to 4 cm in liquid nitrogen.

[0014] Furthermore, the water content of the straw feed exceeds 50%wt.

[0015] The present invention also provides application of low-temperature freezing pretreatment technology in improving the rumen degradation rate of straw feed, wherein the low-temperature freezing is liquid nitrogen freezing.

[0016] Furthermore, the straw feed is crop straw.

[0017] Furthermore, the straw feed includes one or more of corn straw, rice straw, wheat straw, and rape straw.

[0018] Furthermore, the improving the rumen degradation rate includes improving the degradation efficiency of straw feed in the rumen of ruminants.

[0019] Furthermore, the straw feed is completely immersed in liquid nitrogen for pretreatment.

[0020] Furthermore, the pretreatment time is 2 to 8 h.

[0021] Furthermore, the improvement of the rumen degradation rate of straw feed includes dry matter degradation rate.

[0022] Beneficial effects

[0023] To address the industry's low digestibility and utilization rate during straw feed conversion, the present inventors have discovered that ultra-low temperature pretreatment can effectively destroy the straw's fiber structure and increase its rumen degradation rate. Low-temperature pretreatment involves treating the material at a relatively low temperature (typically above -100°C but below ambient temperature) to alter its physical or chemical properties. The low-temperature freezing technology described in this invention effectively increases the rumen dry matter degradation rate of straw feed after pretreatment, promoting its digestion and utilization in the rumen of ruminants. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The effect of liquid nitrogen pretreatment on the dry matter content of straw;

[0025] Figure 2 The effect of liquid nitrogen pretreatment on the water-soluble carbohydrate content of straw;

[0026] Figure 3 The effect of liquid nitrogen pretreatment on the neutral detergent fiber content of straw;

[0027] Figure 4 Electron micrographs of the control group and the group after liquid nitrogen treatment, where a is the control group and b is the group after liquid nitrogen treatment;

[0028] Figure 5 The effect of liquid nitrogen pretreatment on the degradation rate of straw dry matter;

[0029] Figure 6 The effect of liquid nitrogen pretreatment on the dry matter degradation rate of wheat with different moisture contents was studied. DETAILED DESCRIPTION

[0030] The technical solutions provided by the present invention are described in detail below with reference to the examples, but are not intended to limit the present invention. The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0031] Example 1

[0032] Straw harvesting was carried out during the physiological maturity of crops. Maturity was determined by the presence of at least 90% yellowing of rice kernels within the ear, complete yellowing of corn husks, and the disappearance of the milky line in the kernels. Harvested rice and corn straw were promptly transported to the laboratory and chopped to 2–4 cm using a hay cutter. A single-factor, completely randomized experimental design was used. The control group consisted of raw rice straw (RS) and corn straw stems (MS), fresh leaves (M-FL), and dried leaves (M-DL). Fresh leaves were defined as leaves harvested in a naturally extended state with a moisture content of ≥60%, while dried leaves were defined as leaves air-dried to a moisture content of ≤15%. The treatment groups consisted of liquid nitrogen-treated rice straw (LN-RS) and corn straw stems (LN-S), fresh leaves (LN-FL), and dried leaves (LN-DL), with three replicates per treatment. The chopped straw samples are immediately added with liquid nitrogen for ultra-low temperature treatment. The treatment duration is strictly controlled to at least 2 hours. This duration is determined based on preliminary tests to ensure that the straw is fully broken and avoids excessive freezing damage.

[0033] After processing, the sample was immediately split: First, 5g of fresh sample was accurately weighed and placed in a test tube and stored in a refrigerator at -20°C for subsequent water-soluble carbohydrate (WSC) content determination. The remaining sample was quickly transferred to a forced air drying oven and dried at 60°C for 48 hours until it reached a constant dry weight (the difference between two consecutive weighings was ≤0.002g). After drying, the dry matter (DM) content of the sample was determined using a 1 / 10,000 electronic balance. The dried sample was then pulverized using a 40-mesh grinder and passed through a 40-mesh standard sieve (pore size 0.425mm). The pulverized sample was collected, placed in a ziplock bag, and stored in a desiccator until further analysis. Neutral detergent fiber (NDF) was determined using the Van Soest fiber analysis method. From the 5g fresh sample, 0.6g of the accurately weighed sample was used to determine the water-soluble carbohydrate (WSC) content using the anthrone ethyl acetate method. Fresh straw samples, relatively intact, were prepared through appropriate processing, including fixation, dehydration, and critical point drying, to prepare them for SEM observation. The morphology of the straw samples was observed and analyzed using a Geminin SEM 300 Zeiss field-emission scanning electron microscope. This microscope, with its high resolution and magnification, clearly reveals microscopic features such as the straw's surface structure and cell wall morphology. The captured images were processed and analyzed using professional image analysis software to obtain relevant parameters of the straw's morphological structure, providing a direct basis for a deeper understanding of the straw's physical properties.

[0034] For the in vitro fermentation experiment, rumen fluid was collected within 1 hour before morning feeding. Rumen contents were extracted from three cows via rumen fistula using a catheter. The filtrate was filtered through four layers of gauze, mixed thoroughly, and then kept warm at 39°C. The filtrate was then mixed with artificial rumen nutrient solution preheated to 39°C at a volume ratio of 1:2. Approximately 220 mg of dry matter (rice straw and corn straw without liquid nitrogen treatment in the control group and rice straw and corn straw with liquid nitrogen treatment in the treatment group) was weighed and placed in a 75 mL anaerobic fermentation bottle. The sample was then inoculated with 30 mL of the artificial rumen nutrient solution and rumen fluid mixture. After aeration with oxygen-free CO2, the bottle was immediately capped, tightly closed, and quickly placed in a shaker preheated to 39°C. After 72 hours of in vitro fermentation, the anaerobic fermentation bottles were removed and placed in an ice-water bath to terminate fermentation. The fermentation substrate in the bottle is collected, the pH of the fermentation substrate is measured, and then the fermentation substrate is dried and weighed for determination of dry matter digestibility (DMD). By measuring DMD, the degree of digestibility of straw under in vitro rumen fermentation conditions can be evaluated, providing an important basis for evaluating the nutritional value and availability of straw.

[0035] like Figure 1 As shown in the figure, after liquid nitrogen cryogenic treatment, there is no significant difference in the dry matter DM content of different straws, indicating that liquid nitrogen cold treatment does not reduce the dry matter content of straw feed. Water-soluble carbohydrates (WSC) in roughage is one of the key indicators for evaluating its nutritional value and has an important impact on the digestion metabolism, rumen health and production performance of ruminants (such as cattle and sheep). Figure 2 As shown in the figure, after liquid nitrogen cryogenic treatment, there is no significant difference in the WSC content of different straws, indicating that liquid nitrogen cryogenic treatment does not reduce their WSC content. NDF is an important indicator of fiber quality and palatability, which can reflect the palatability of roughage. Figure 3 As shown in the figure, liquid nitrogen cryogenic treatment does not affect the NDF content of straw feed. In summary, liquid nitrogen cryogenic treatment does not significantly affect the chemical composition of straw feed.

[0036] Under the electron microscope, it is possible to clearly see whether the surface structure of the straw has changed after being treated with liquid nitrogen. Figure 4 As shown in the figure, compared with the control group, the fiber structure of the straw was changed after liquid nitrogen treatment, and the arrangement was looser.

[0037] In vitro gas production is a commonly used feed evaluation method. Feed samples are fermented with rumen fluid in a simulated rumen environment, and the fermentation characteristics of different feeds are reflected by calculating gas production and feed digestibility. Figure 5 As shown in the figure, the dry matter degradation rate of rice straw and corn straw was significantly improved after liquid nitrogen low-temperature treatment.

[0038] Example 2

[0039] Wheat straw was harvested at maturity and promptly transported to the laboratory. Straw was chopped to 2–4 cm using a hay cutter. A one-way ANOVA design was used. The control group consisted of wheat straw in its natural state without liquid nitrogen treatment (CK). The treatment groups included air-dried wheat straw without liquid nitrogen (LN0), wheat straw sprayed with water to a moisture content of 50% and then treated with liquid nitrogen (LN50), and wheat straw sprayed with water to a moisture content of 70% and then treated with liquid nitrogen (LN70). Each treatment was replicated three times. Wheat straw in each treatment group was immediately exposed to liquid nitrogen for at least 2 hours after chopped. This treatment duration was determined based on preliminary experiments to ensure changes in cell wall structure without inducing chemical degradation. The treated samples were immediately dried in a forced air drying oven at 60°C for 48 hours to constant weight, and the dry matter content (DM) was determined. The samples were then ground using a 40-mesh grinder. The ground samples were then used for in vitro fermentation experiments. After 72 h of in vitro fermentation, the anaerobic fermentation bottles were removed and placed in an ice-water bath to stop fermentation. The fermentation substrate in the bottles was collected, dried, and weighed for determination of dry matter digestibility (DMD).

[0040] like Figure 6 As shown in the figure, the dry matter degradation rate of wheat straw can be significantly improved after liquid nitrogen low-temperature treatment, and the dry matter degradation rate shows a numerical trend with the increase of the moisture content of wheat straw.

[0041] The present invention applies low-temperature freezing technology to the processing and modulation of straw feed for the first time. Liquid nitrogen pretreatment can improve the fermentation of straw feed in rumen fluid by changing the arrangement of straw feed fibers, loosening the straw feed fiber structure, and thereby improving the dry matter degradation rate of straw feed.

Claims

1. A pretreatment method for improving the rumen degradation rate of straw feed, characterized in that: The pretreatment method comprises: freezing the straw feed with liquid nitrogen before feeding the straw feed.

2. The pretreatment method for improving the rumen degradation rate of straw feed according to claim 1, characterized in that: The straw feed includes one or more of rice straw, corn straw, wheat straw, and rape straw.

3. The pretreatment method for improving the rumen degradation rate of straw feed according to claim 1, characterized in that: The improving the rumen degradation rate of straw feed includes improving the dry matter degradation rate of straw feed.

4. The pretreatment method for improving the rumen degradation rate of straw feed according to claim 1, characterized in that: The method of increasing the rumen degradation rate of straw feed includes increasing the degradation efficiency of straw feed in the rumen of ruminants.

5. The pretreatment method for improving the rumen degradation rate of straw feed according to claim 1, characterized in that: The method of improving the rumen degradation rate of straw feed includes changing the arrangement of straw feed fibers, loosening the fiber structure of straw feed, and promoting the fermentation of straw feed in rumen fluid.

6. The pretreatment method for improving the rumen degradation rate of straw feed according to claim 1, characterized in that: The liquid nitrogen freezing time is 2~8h.

7. The pretreatment method for improving the rumen degradation rate of straw feed according to claim 1, characterized in that: The liquid nitrogen freezing of the straw feed comprises completely immersing the straw feed cut into sections of 2 to 4 cm in liquid nitrogen.

8. The pretreatment method for improving the rumen degradation rate of straw feed according to claim 1, characterized in that: The water content of the straw feed exceeds 50%wt.

9. Application of low-temperature freezing pretreatment technology in improving the rumen degradation rate of straw feed, wherein the low-temperature freezing is liquid nitrogen freezing.

10. The use according to claim 1, characterized in that The liquid nitrogen freezing time is 2 to 8 hours.

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