1. Foreword Grain Feed Is an important energy ruminant material. Seeds of the common grains,
Starch The content is higher (about 52% -78%), easily digested and absorbed by an animal, and the use of high efficiency. Starch degradation in the rumen to volatile fatty acid end products (vfa), vfa nutritional significance is able to provide the energy needs of ruminants 70% -80%. Nearly 40 years, as some Western countries, the price of feed grain prices lower than the hay, grain products is widely used as the main feed ruminant animal production. In China, the grain feed is also widely used, but the price is usually higher than the hay. Generally speaking, processing can be improved to some extent, rumen microbes and nutrient utilization efficiency of the total digestive tract (HAN Zheng-kang, 1988), therefore, for processing of grain feed to increase their utilization of research is necessary.
2. Cereal starch nutritional physiology and the need for processing
Starch in the rumen by microbial fermentation of most vfa, part of the vfa as the carbon frame was integrated into microbial protein; another part of the vfa been absorbed into the blood involved in metabolism of the rumen. Rumen degradation of starch is not directly enter the abomasum and small intestine (rumen starch), under the action of digestive enzymes in the decomposition of glucose after absorption. Small intestine is not the absorption of starch and glucose, after entering the colon is microbial fermentation, some absorbed, eliminated from the body.
Rapid degradation of starch in the rumen, only a small amount of starch can escape ruminal fermentation directly into the small intestine (about 10% -30%), and the rapid formation vfa rumen will reduce the ph value, thus undermining the rumen the normal fermentation, resulting in feed imbalance between decomposition and microbial synthesis. Maintain a certain percentage of starch in the rumen for the effective use of n sources and enhance the efficiency of microbial protein synthesis is necessary, but excessive starch fermentation in the rumen in the rumen may lead to changes in the environment affect the efficiency of nutrient use, and even lead to metabolic diseases . If the diet part of the non-structural carbohydrates nsc (starch and non-starch polysaccharides, etc.) to avoid rumen fermentation, animal productivity will increase (bruchem, 1991). Escaped rumen fermentation nsc because not only can provide more glucose for the animals, but also to prevent the loss of rumen fermentation (tamminga, jansman, 1993); for the animals in the glucose could serve as an important precursor of lactose, save the use of amino acids, and Cow’s milk production can increase.
On feed grain for processing to a certain extent, regulation of ruminal starch degradation of starch and the ratio of rumen to the production of animal produce the best performance.
3. Processing on nutritive value of cereal starch and its possible mechanism
Processing can change the digestion of starch in the digestive tract and digestive site level (huntington, 1997). Many processing methods, including physical processes (eg, puffing? Baking? Granulation? Broken? Ground? Rolling? Vapor film, etc.), chemical processing (such as alkali treatment) and biological processes (eg,
Enzyme ) And so on. Application of current production is more physical processing of grain feed. Processing time, temperature, moisture content and particle size will affect the processing of results.
Starch surface by a protein matrix and surrounded by fat, the surface sometimes have jagged? Minor groove? Cracks or holes, as microbes and enzymes to attack sites. Some processing methods (broken? Ground? RCC) can be broken grain particles in the testa, reduced to particles, surface area, increasing rumen microbes and enzymes to enter the chance to speed up the rate of rumen digestion of starch, thus improve its nutritional value.
Raw starch ( -amylase) of the elements closely arranged, to form a cystic capsule, the gap between small, but when heated in water, part of the capsule will be dissolved to form a gap, water molecules can thus penetrate starch elements of the internal; then continue heating to the gelatinization temperature, the capsule will all collapse, molecular bond breaks, the formation of gelatinized starch ( -amylase) more easily digested. Expansion is when the water is high temperature and pressure conditions, the sudden decompression, instant vaporization, fill in the gap of water produced within the Expanded strong force to promote volume expansion and the starch was porous.
Different processing methods would rumen degradation rate of starch grains changed. In most cases, treatment with a combination of steam and stripping (for example, flaked, extruded extrusion) can rumen starch degradation rate, while the baking makes rumen starch degradation rate was significantly lower (nocek, tamminga, 1991).
Most of the processing methods to increase starch degradation in the rumen, usually to the small intestine in the digestion of starch increased, sometimes to the increase in rumen starch more favorable (owens, zinn, kim, 1986). And fine grinding of corn compared to corn fed whole grain starch to rumen degradation rates; larger particles of the starch may be less susceptible to enzyme digestion in the small intestine, and large particles and the density of corn grain flow speed so that the whole gastrointestinal degradation rate. (Owens, zinn, kim, 1986).
Processing must master a “degree”, or go overboard. High-temperature long working hours, excessive protection may make starch, carbohydrate and amino acid Maillard reaction (millardreaction), the formation of complex compounds, neither the degradation in the rumen can not be digested in the small intestine.
4. Corn starch processing applications in the dairy production
It y.ying reported in the dry period and lactation fed high moisture corn (hmc), can improve rumen digestibility of organic matter and starch to increase the concentration of rumen vfa. As the feeding hmc, reduce the outflow rate of rumen digesta to improve the starch digestibility, but the entire digestive tract starch digestibility was no increase. rbreis that feeding hmc and fine grinding of corn, to improve the digestive organs of cow’s dry matter (dm) and starch digestibility, increased milk production. bpglem reports, hmc: dc (low-moisture corn) is 6:4, the increased dry matter intake (dmi) and milk yield.
Lgnussio, who found that treatment with the vapor pressure tablets (sf) of corn, increasing the effect of starch digestibility than fine handle smashed, but there rumen ph value and digestibility of cellulose decreased strength, despite the increase in the milk yield, but milk fat percentage decreased. huber that fed crushed flakes processing of sorghum in the rumen degradation rate is higher than other processing methods, the best test results. Compared with the untreated sorghum, although milk BOLA TANGKAS