Occurrence and control of PSE pork

Introduction: Bu rile, Wu Jinhua (School of animal science and technology, Inner Mongolia University of nationalities, Tongliao 028042, Inner Mongolia) Chinese Library Classification No.: s828.91 document identification code: B Article No.: 0529-5130 (2002) 05-0022-02 PSE pork refers to the appearance of slaughtered pork, which is pale (muscle), soft and inelastic, and exudative on the surface of muscle These main characteristics differ in degree of performance With the development of China's feed industry, the introduction and improvement of breeding pigs, and the improvement of feeding management level, China's pig industry is booming in terms of both scale and number of stocks In 1998, China had a population of 1.256 billion, 472 million pigs were put on the market, with a pork output of 36.93 million tons and a per capita pork output of 29.41 kg, which exceeded the world average of 14.27 kg The output of both pigs and pork accounted for the first in the world However, due to the simple pursuit of weight gain and yield, the quality of pork has a downward trend, and the incidence of PSE pork has increased So we should attach great importance to PSE meat 1 The cause of PSE pork 1.1 Pre natal stress 1.1.1 physiological stress It is reported that the incidence of PSE meat in captive pigs is higher than that in bulk pigs This shows that the adaptability of pigs in captivity to the changing environment is weaker than that of free pigs Factors such as driving, binding, loading, transporting before slaughter, biting each other in the trunk, driving and stopping, too high and too low temperature, lack of nutrition and water shortage will make the pig body temperature too high, speed up the glycolysis process, increase the production of lactic acid, and finally lead to PSE meat l 1.2 the stress of slaughtering and fainting during slaughtering are also one of the important reasons All the methods of fainting can make the body release catecholamine suddenly, enter the blood and produce muscle contraction However, the incidence of PSE meat was different with different methods of stunning The stress produced by binding fainting was the largest, followed by CO2 anesthesia The stress of electric fainting was moderate, and that of animals without binding fainting was the smallest Therefore, the high-pressure radio halo method is widely used in American Meat factories 1.2 postmortem changes when carcasses (or carcasses) are exposed to high temperature It can speed up the fermentation process of sugar in muscle, generate heat, and increase the temperature of carcass to 40-42 ℃ in a certain period of time to increase the production of lactic acid When the pH value is medium or lower than 5.9, and the temperature of carcass is higher than 35 ℃, the muscle protein will denature and become PSE meat In addition, soaking in hot water at 63-65 ℃ for 2-3 min can also increase the meat temperature and promote the occurrence of PSE 1.3 Hamori thought that heredity and environment are also one of the factors that cause PSE Although the exact genetic mechanism has not yet been determined, the differences in PSE meat incidence among many different breeds of pigs fully show that it can not be doubted that they are affected by heredity 2 The commercial economic characteristics of PSE pork According to the statistics of meat factories in different regions, the incidence of PSE meat of imported pigs is high, followed by that of Hybrid Pigs, while that of local pigs is less The incidence of PSE pork in the United States is about 5% - 20% The investigation of small and medium-sized livestock farms in niaozhu County, Japan shows that the incidence of PSE pork is 30% - 4O%, some of which are 60% - 70% PSE pork mainly occurs in muscle parts with high commodity value The color of the cross-section is white, lustrous, edematous and fleshy, the muscle tissue lacks elasticity, the recovery ability is reduced, the tightness of the muscle bundle is reduced, the muscle bundle is separated, the texture of the muscle bundle is rough, the meat quality is soft, and the muscle fiber of the hand pinch is fragile Microscopically, the changes were as follows: the muscle fiber was loose, the space between muscle fibers was enlarged, there was a lot of water, and there was no inflammatory cell (but domestic scholars believed that PSE meat occurred in China had inflammatory cell infiltration) These organizational changes have greatly influenced the value of commodity economy Because the appearance is not beautiful, such as boiled meat, it is called "boiled meat" The water loss rate is 4% - 5% higher than that of normal meat It is not suitable for deep processing and low yield It is reported that the loss rate of stress-induced pigs in transportation is 4.7% - 10.3% or more The daily gain of this kind of pig is 45g lower than that of the healthy pig, but the feed reward is not decreased In addition, the retail block of PSE meat is difficult to see because of the excessive water seepage and the accumulation of water drops on the edge of the package In the process of display, this kind of meat is more prone to rancidity than normal pork In addition, compared with normal pork, PSE pork is not good in color, taste, juiciness and overall taste, so consumers generally do not welcome this product It is reported that the annual loss caused by the deterioration of meat quality in the United States amounts to 400-600 million yuan 3 The examination of PSE pigs generally believed that the pigs had certain characteristics in appearance, such as short and thick limbs, plump muscles, over developed chest, over plump hindquarters, over obese whole body, firm skin, protruding eyes, neuroticism, excitability, fear and aggressiveness During the test, when the appearance is observed, the enzyme activity in the serum of the pig is measured after the pig is quiet or has received the stress reaction for a certain time If it is increased, it is positive The current method in foreign countries is to use halothane gas for inspection Halothane is an anesthetic A suction device with an urethane mask is used for inspection First, the assistant Baoding pig will land on the abdomen The assistant sits on a high stool, clamps the two legs on both sides of the pig body, holds the pig's forelimbs with both hands, and lifts them up The surgeon can cover the pig's mouth and nose with a halothane mask The concentration of inhaled halothane was 1.5% - 5% (6% in Japan) The mixed oxygen was 1500-2500 ml / min and observed for 3 min The piglets were examined once at 21 days and 56 days after birth In the case of positive pigs, progressive muscle spasm and rigidity were found at 3 min after inhalation of halothane, and the hindquarters were obviously stiff; in the case of positive pigs, no rigidity was found at 3 min after inhalation of halothane This method is effective and economical In recent years, many countries have conducted halothane tests on pigs of different breeds or strains The results show that the positive rates of pietrane and Landrace in Belgium are 50% - 100%; Hampshire and Landrace in most regions in the United States are the second; Duroc and Yorkshire are the second These data are of great reference value to our introduction 4 Control strategy 4.1 Breeding of resistant strain of stress syndrome Breeding pigs with hereditary stress response are easy to produce PSE meat, which should be eliminated in time To find out the parents of pigs with PSE muscles, and to eliminate them after confirmation According to the data, the incidence of stress pigs has been reduced from 30% to less than 3.5% by halothane detection and screening abroad In order to make full use of the lean meat type pigs such as pietran and Landrace and the varieties with high meat production performance, and overcome the characteristics of high PSE meat incidence, the crossbreeding of stress resistant boar can be used When the three varieties are crossbred and backcross, as the last round of boar and homozygous maternal line, the incidence of PSE meat in the later generation can be greatly reduced 4.2 pay attention to the veterinary health management, reduce the adverse stimulation before slaughter The transportation from the origin to the slaughterhouse can make more pigs appear stress response Therefore, it must be managed according to the requirements of veterinary health As far as possible to avoid rough behavior on pigs, avoid loading too dense, long-distance transportation, avoid loading and unloading in hot weather 4.3 use drugs to prevent and treat stress Before transportation, add ve to the feed, or feed chlorpromazine (hibernating spirit) for 1-2 days The dosage is 1mg / kg body weight, which can play a preventive role The mechanism is to enhance the inhibition of the central God system of pigs, so as to enhance the adaptability of pigs to the external environment and reduce the stress response The therapeutic dose was 1-2mg / kg body weight In the early stage of PSE, it can be treated with corticosteroids and sedatives, which has certain effect Xqt (author:) to feed Weibo to: