How do the "double-edged arrows" of nutrition and environment affect the meat quality of livestock and poultry?

Zhang Baoquan

With the improvement of living standards, people are not only pursuing safe and nutritious green livestock products, but also have higher and higher requirements for meat quality. Therefore, farmers need to improve their products in order to produce healthy foods that meet human needs. The factors affecting the quality of livestock and poultry meat include breed, genetics, nutrition, environment, management, stress, slaughter, etc. Among them, nutrition and environment are the most controllable by farmers, and the meat quality commonly referred to mainly refers to the senses, processes, and meat of meat. Sanitary quality, ie muscle pH, flesh, water, tenderness, flavor and other indicators. Therefore, study the influence of meat quality nutrition and environmental factors. Exploring ways to improve meat quality is of great importance to the aquaculture industry.

I. Commonly used evaluation indicators of meat quality

1. Flesh color

Flesh color has little effect on the nutritional value of meat, but it affects the appearance of meat and the desire of consumers to purchase. It is a comprehensive indicator reflecting changes in muscle physiology, biochemistry, and microbiology. The color of the meat depends on the pigment substance myoglobin in muscle (Mb (About 70% to 80%) and hemoglobin (Hb, about 20% to 30%) content, ferrous ions in Mb combine with oxygen to form oxygenated Mb, the meat is bright red, while Mb and oxygenated Mb All can be oxidized to produce high-iron Mb, and the flesh is darkened and brown.

2. flavor

The flavor of meat mainly includes both taste and aroma. The taste is a soluble substance that dissolves in water. It stimulates the taste buds on the tongue and reacts to the brain through the nerves. The taste of meat comes from the nucleotides and amino acids in the meat. Precursors such as amides, organic acids, sugars, fats, etc.: The fragrance is mainly produced by the volatile substances such as alcohols, aldehydes, ketones, acids, and esters produced during the heating of muscles. The flavors are mainly related to animal species, age, and gender. , nutritional status, environmental factors and post-slaughter handling.

3. Tenderness

Tenderness refers to the sensation during the chewing process at the entrance of the meat, mainly from the softness of the meat to the tongue or cheek, the resistance of the meat to the pressure of the teeth, the ease of breaking the muscle fibers, the remaining amount of meat residue after chewing, and the amount of chewing after chewing Measured by the amount of time it takes to swallow. Tenderness is also positively correlated with intermuscular fat. Muscle tenderness is directly related to animal species, age, muscle location, nutritional status, environmental factors, and post-slaughter processing.

4. Water power

The water power of meat refers to the ability of the meat to retain its original moisture under the influence of external factors such as pressing, heating, chopping and stirring. Water depends mainly on the reticular structure of myofibrillar proteins and the amount of static charge that the protein carries. When the protein is in an expanded colloidal state, the network space is large and the water pressure is high. On the contrary, the hydraulic force is reduced. For meat, the net charge increases and the water pressure increases. On the contrary, the hydraulic force is reduced. There are many factors affecting the muscle water system, mainly pH value, animal environmental factors, processing of animal products, etc.

5. pH

After animal slaughter, aerobic respiration stops, energy metabolism is converted to anaerobic glycolysis pathway, and glycolysis in the muscle produces lactic acid, which causes the muscle pH to decrease. The pH value is also related to the processing methods before and after slaughter. Slaughter stress causes the animals to be highly excited and arrogant. The glycolysis is strengthened and excessive lactic acid is produced. The pH of the muscles is drastically reduced. A long period of hunger strikes and muscle exercises before slaughter will occur. The glycogen in the muscle is depleted and almost no lactic acid is produced, and the pH is high.

Second, nutrition and environmental factors that affect meat quality

1. Nutritional factors that affect meat quality

1.1 Dietary protein and energy levels

Dietary protein levels had a certain effect on pork quality. Only pigs fed high-protein diets had reduced body fat and increased muscle mass. Reducing the intake of protein can lead to increased carcass fat content. With the increase of protein or amino acid levels, the lean meat percentage increases significantly but the tenderness of meat decreases. Therefore, the energy and protein should be in the best balance in production, and the type of dietary fat directly affects the type of pork fat. For example, pigs fed corn diets have high levels of unsaturated fatty acids and health care functions, but are susceptible to oxidative deterioration. Pigs fed a barley diet had high levels of saturated fatty acids in body fat. Detrimental to human body. But resistant to transport.

1.2. Amino acid levels

Lysine has no effect on muscle fiber types, but it can increase muscle volume and muscle fiber diameter, increase longissimus muscle area, and reduce tenderness. After the weaning, the glutamic acid in the plasma will decrease. Therefore, we need short-term glutamate supplementation during weaning to improve the growth performance and carcass quality. The addition of tryptophan can effectively solve the problem of PSE meat (meat pale, soft, juicy) associated with pre-slaughter stress (Ball, 1988; Warner, 1990). Warner et al. (1990) showed that addition of tryptophan (5 g/kg diet) to the diet during the first 5 days of anaemia could increase the hypothalamus serotonin concentration and reduce pig aggression in the pre-slaughter circle. , thereby reducing swollen pigs and PSE meat problems.

1.3. Vitamins

Addition of vitamin E in the diet can effectively inhibit the formation of methemoglobin in fresh meat, enhance the stability of oxidized hemoglobin, and extend the preservation time of fresh meat. Buckly et al. (1995) pointed out that adding high doses of vitamin E in feed can significantly inhibit pork fat and cholesterol oxidation. Winne and Dirinck (1996) found that adding vitamin E can increase muscle flavor and freshness. There is a difference in the meat score and the muscle tastes more fresh. Supplementing a large amount of vitamin C in the diet can slow the rate of muscle pH drop after slaughter. Improve pork quality. Swanek (1997) reported that supplementing 7 500 IU/d of vitamin D to beef can improve beef tenderness 5 to 10 days before slaughter. Figg (1977) reported that adding biotin to growing pig diets can increase the saturation and tenderness of pork fat

1.4. Minerals

By supplementing chromium, muscle glycogen consumption can be reduced, thereby reducing lactic acid production, reducing pre-slaughter stress, and preventing the production of PSE meat. Mooney and CrenWell et al. (1995) found that chromium supplementation in growing pigs increased muscle production and lean meat percentage, and reduced total fat and fat. Magnesium can reduce the neuromuscular stimulation produced by calcium, reduce the cholinergic secretion caused by nerve impulses, and can also reduce the release of nerve endings and adrenal catecholamines and improve meat quality by inhibiting the glycogen decomposition reaction caused by pre-slaughter stress. Munoz et al. (1996) reported that adding 0.1 mg/kg selenium to a growing pig diet and adding a certain amount of vitamin E and vitamin C at the same time can reduce the drip loss of longissimus dorsi muscle. Increasing the content of iron and copper in feed can increase the activity of superoxide dismutase in muscle. Reduce the damage of free radicals on meat products, thus improving the quality of meat, but the amount of copper and iron in the diet should be strictly controlled. Greene et al. (1989) showed that carcass quality classification, marble score, and peripelvic and pericardial fat content of 360 mg zinc (methionine zinc) calves per day in yak diets were significantly higher than those in the same amount of zinc supplements. Zinc group and control group without zinc addition.

1.5. Other nutrient additives

L-carnitine can participate in the oxidative decomposition of fat in the body to generate adenosine triphosphate (ATP), which can increase the umami taste of meat. It can also increase the breast muscle Mb content, improve the color of the meat. Betaine improves meat quality by increasing carnitine synthesis in animals. Saccharicterpenins have the effects of scavenging free radicals and antioxidants. The proportion of rice bran added to the feed has been reduced to lighter meat, the meat has become softer, and PSE meat has been easily produced. The meat products are susceptible to rancidity and reduce the shelf life. Fishmeal, rapeseed meal, and choline, which are widely used in chicken feed, can cause offensive odors in poultry and poultry meat.

Therefore, the flavor and tenderness of livestock products can be improved by changing various nutrient contents in the diet.

2. Environmental factors affecting meat quality

Strengthening feeding and management, reducing breeding density, and greening the environment can reduce various bad odors in the environment, take animal welfare seriously, allow animals to live in a comfortable environment, reduce stress, and improve meat quality. So how to create a good environment for farm animals?

The most primitive way of farming is free-range, and pigs are free to eat freely. Everyone knows that ordinary rural free-range pork is very tasty, but the prevention of disease is very difficult to do. With the emergence of intensive and large-scale farming methods, the growth of animals Environmental constraints, many factors greatly affect the quality of meat, but the recent rise of the ecological breeding of the fermentation bed has improved the treatment of pigs, such as Jinbao dry fermentation bed economically cost-effective, technically feasible, to bring farmers Great economic benefits and social environmental benefits. The benefits of ecological fermentation bed:

2.1 Deodorization The functional microbes in the environmental fermentation bed break down the excreta within 2-3 days (and complete it in a few hours), the pigsty becomes clean, the environment is improved, and the environment is not fouled, and the contamination is minimized on the spot. , Zero emissions, in full compliance with the state's environmental requirements for aquaculture pollution, with such a mode of farming, but also worried about the "ban order, restrictions on pigs" it?

2.2 The surface temperature of energy-saving grain-fermentation bed is kept at 20 degrees for many years, so that heating and heating costs can be saved in winter. Microorganisms convert fecal urine as nutrient source into bacterial protein, which is a very good food for pigs. This is called The pigs not only have staple foods, but also snack foods. For example, the Jinbao fermentation bed can save more than 100 pounds of feed per pig on average.

2.3. Water-saving laborers use fermentation bed culture to avoid excrement-free flushing. In addition to the normal drinking water of pigs, it saves 75% to 90% of water, saves 30% to 50% of labor, and completes the work in a few hours every day. Heaven's live.

2.4 Anti-disease promote long fermentation There are a large number of beneficial microorganisms and fermentation crude growth factors in the bed. Pigs eat to improve intestinal health and increase resistance to disease. In addition, the cement floor is hard and often flushed against pigs compared to traditional culture. The growth is very influential, the environment is improved, and the treatment is increased. Therefore, pigs do not get sick and gain weight quickly. On average, each pig gains 10-15 kg more.

2.5. Increased Economic Benefits Ecological Fermentation Bed Breeding Water, electricity, labor costs, provincial feed fees, and provincial drug fees have saved a lot of money. At the same time, the quality of pork produced is also good for a good price. Economic benefits. In addition, you can enjoy national policies.

The following is an experimental report on the quality of meat in fermented bed pigs:

Table 1 Effects of Fermented Bed Breeding on Pork Quality

Fermentation bed group

Conventional culture control group

Improvement rate (%)

Pre-slaughter weight (kg)

96.80.28

890.22

8.76

Slaughter rate (%)

73.512.24

72.852.21

0.91

Lean (%)

65.042.09

63.343.22

2.68

PH value

6.120.25

5.930.14

3.2

Flesh color (points)

3.50.11

2.90.12

20.69

Loss of water (%)

7.163.24

8.122.28

-11.82

Intramuscular fat (%)

1.370.11

1.40.17

-2.14

Marble (minutes)

3.240.22

2.650.22

22.26

Eye muscle area (cm2)

36.61.73

42.151.83

-13.17

Back thickness (cm)

1.640.28

1.770.30

-7.34

Rear leg ratio (%)

31.580.36

31.480.39

0.32

As can be seen from the above table, the fermentation bed culture has greatly improved the meat quality, such as a 20% increase in flesh color, a ruddy flesh after slaughter, and a clear texture, which is superior to ordinary pork. The water rate has increased by 11.82%. It has also played a very good role in other aspects. It has also extracted tenderloin meat and hind leg meat. Its amino acid and other nutrient contents have been increased by 10% to 15%, respectively, and it has completely achieved the pollution-free pork standard. ,

Due to the fact that the pigs only recovered their natural habits, the pigs had less stress, and they also ate the bacterial protein and beneficial bacteria, which greatly improved the balance of the intestinal flora, significantly increased the resistance to disease, and reduced the incidence rate, especially respiratory diseases. Compared with traditional intensive feeding, gastrointestinal diseases have drastically decreased, and the cost of medication has been reduced by 8 to 15 yuan per head. The pork produced by the ecological fermentation bed is of good quality without drug residues. Such as the combination of local high-quality pig production, open up a new channel for the development of high-quality pork industry.

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