The summary summarizes the effect of copper on improving pig performance and the mechanism of growth promotion. Adding copper 62.5～250mg/kg to the feed can significantly promote the growth of piglets and reduce the feed consumption per unit weight gain, but the growth promotion effect of copper decreases with the increase of piglets age. The growth-promoting effect of copper on pigs is likely to be systemic, not limited to the role of gastrointestinal microbes; suggesting that high-efficiency new organic copper sources should be developed, developed and applied in pig production to maximize copper-to-pig Promote growth effects while reducing environmental pollution from copper emissions.

Key words copper; pig; production performance 3 growth promoting mechanism

Copper is one of the essential trace elements of humans and animals. The nutritional requirements are: 2 to 3 mg/d for adults; 5 to 10 mg/kg for mammals; and 4 to 11 mg/kg for poultry [1]. Usually, people supply copper to animals according to their nutritional needs, but under special requirements, the amount of copper supplied varies depending on the needs and the functional state of the animal. Since Braude (1945) first discovered that the addition of high-dose copper to diets has promoted growth in young pigs, much research has been done on the growth-promoting effects of high-copper on pigs and has been a hot topic in animal nutrition. Tests have shown that as long as the nutritional balance of the diet and other related factors are considered, the addition of 125-250 mg/kg copper (especially 250 mg/kg) has obvious growth-promoting effects on various stages of pigs (especially early growth stages). At present, in the production of pigs at home and abroad, the use of high-copper as a growth-promoting feed additive for pigs has become quite common. Since the copper in the feed is excreted from the feces and the copper is non-degradable, it is feared that long-term use of high copper will cause the accumulation of copper in this area and destroy the ecological balance. At present, the mechanism of action of high copper on pig growth is still not refined. Bowland (1990) and Qiu Huasheng (1992) have made detailed reviews on the growth-promoting effects, influencing factors, tissue residues, toxicity and environmental pollution of pigs at various stages [2]. In this paper, an overview of the latest developments in copper production performance and possible growth-promoting mechanisms is presented. In order to further study the mechanism of promoting the promotion of high copper, the role of copper is recognized, and further studies are conducted to study the non-polluting alternative growth of copper. Provide a theoretical basis. It also provides a valuable reference for the scientific use of high-copper growth promoters in pig production in China.

1 Effect of high copper on improving pig performance

When the zinc and iron in the feed are kept at a certain level (150mg/kg), the addition of copper 62.5-250mg/kg (copper sulfate form) in the diet can significantly promote the growth of piglets and reduce feed consumption. This characteristic of copper is widely used. Used in suckling food and piglet growth. The addition of copper 125-250 mg/kg to piglet diets has been widely recognized for improving piglet growth performance. However, different researchers have different results depending on the type of animal used, the type of feed, the weight of the animal and the nutritional level of the diet [3]. The dietary copper addition amount was 62.5-250mg/kg, the average daily gain of piglets increased by 13.14%, and the unit weight gain and consumption decreased by 8.62%.

Eating high-copper diets also affects the performance of sows. Adding 250mg/kg of copper to the Yorkshire × Hampshire hybrid sow diet, 81 litters of statistical results show that the average litter size, average litter size, average birth weight, average first life pig weight, live The number and average weaning weight were 6.75%, 2.93%, 6.12%, 7.83% (P<0.02), 0.87% and 5.14% (P<0.02), respectively, and the number of days from weaning to estrus was shortened by 0.87d. Cromwell, 1992).

Dietary copper supplementation also affects the body quality of growing and finishing pigs. Adding 185mg/kg of copper to 20kg Changbai × Min pig F1 diet can significantly improve the quality of copper body [3], reduce skin thickness by 15% (P<0.05), increase eye muscle area by 13%, and muscle in 8 kinds. The total content of essential amino acids increased by 6.16%.

2 Mechanism of copper-promoting growth

2.1 Antimicrobial effect of copper

The growth-promoting effect of copper may be related to its antimicrobial action in the gastrointestinal tract, and high-dose copper (in the form of copper sulfate) also has an antibacterial effect. The addition of copper 250mg/kg to the growing pig diet can reduce the total number of bacteria in the feces by 60 times [4]. High-dose copper sulfate resistant mold (Johnson, 1985); adding 200mg/kg copper to the diet is beneficial to remove the large intestine that is resistant to oxytetracycline, streptomycin, ampicillin, kanamycin, etc. Bacillus (Istrazivacki et al., 1990). In addition, high doses of copper sulfate reduced coccidiosis infection in broilers (Bafundo, 1983). The growth-promoting effects of copper are similar to those of several commonly used antibiotics [5]. As the pig ages, the reduction in copper growth is similar to the reduction in antibiotic growth [6]. The growth-promoting effect of copper and antibiotics is additive, and their effect at the same time is better than that when they are used alone [7]. The diet was supplemented with 250mg/kg copper alone, and antibiotics were used alone. When combined, the growth rate of weaned piglets increased by 19.30%, 15.79% and 31.58%, respectively; the feed-to-weight ratio increased by 9.05%, 7.14% and 12.38%, respectively; feed efficiency Increase by 7%, 6% and 10% respectively (Cromwell et al., 1991). He inferred that this may be due to the fact that copper has a broader spectrum of antibiotics than those measured in these studies, or that copper has a different effect than the antibiotics. Miller (1979) proposed the hypothesis [8] that copper inhibits the growth of beneficial microbial flora by inhibiting intestinal microflora, and alters the characteristics of intestinal microflora. However, there have been no reports of the effect of growth-promoting copper on the number of different microorganisms in the feces. Studies by Fuller et al. (1960) and Smith et al. (1963) showed that the addition of copper had no effect on microorganisms in the feces [6, 9]. Underwood (1977) studied a number of experimental results and pointed out that dietary copper is not significantly promoted by inhibiting or promoting gastrointestinal microbes [10]. It can be seen that the antimicrobial action of copper still needs further study.

2.2 Copper can increase feed intake

The increase in pig feed intake plays a major role in the growth-promoting effects of high copper [11]. The diet containing 214 mg/kg copper significantly increased the feed intake within 14 days after weaning, which significantly increased the daily weight gain of weaned piglets; and in the 200 mg/kg copper group, the limit feeding was significantly higher than that of free feeding. Limiting the feed intake of weaned piglets (about 80% of free-feeding) greatly limits the growth-promoting effects of high copper. Studies by Hedges et al. (1973), Edmonds et al. (1985), Komegay et al. (1989), Dove and Haydon (1991), Dove and Haydon (1992), Dove (1993), etc. also showed [6, 12], copper versus pig. The growth-promoting effect is closely related to the increase in feed intake. The mechanism by which copper causes an increase in pig feed intake is unclear. Pan et al (1986) injected intravenous copper into rabbits to stimulate the secretion of neuropeptide Y hormones in the hypothalamus, a hormone that strongly promotes pig feed intake [13]. Therefore, high copper is likely to cause an increase in pig feed intake by stimulating the secretion of Y hormones in the hypothalamic neuropeptide of pigs. However, further direct research is needed on pigs. If the above hypothesis is confirmed in pigs, then the necessity of adding high-dose copper to pig diets will be questioned because other attracting agents similar to high-copper can be used to achieve the same purpose while avoiding excess The problem of environmental pollution caused by copper discharge.

2.3 Copper participates in the role of enzyme system

Such as Zapsalis and Beck (1985), Sorenson (1987) and other reports [9,14], since copper is used as an essential component of several copper-dependent enzymes and a cofactor of a large number of other enzymes in animals, it plays a biochemical function. Pig growth may be promoted by one or a combination of the following pathways: (1) stimulating enzyme activity associated with nutrient digestion and utilization, improving nutrient digestion and utilization. The diet supplemented with copper 125mg/kg, the pepsin activity of piglets increased by 7.95% compared with the control group supplemented with copper 4mg/kg (Liu Guilin, 1994); (2) stimulated antioxidant enzymes in the body (such as glutathione peroxide) Enzyme, GSH-PX; copper-zinc superoxide dismutase, CuZn-9OD) activity, anti-oxidation and anti-stress, improve the immune resistance of pigs, Liu Wei (1992) reported that the diet added copper 62.5, At 125 and 250 mg/kg, the blood GSH-PX activity increased by 4.49%, 27.53% (P<0.05) and 38.76% (P<0.05), respectively, after feeding for 25.13 kg of pigs for 30 days. <0.01). Cu 125-kg (or 250 mg / kg) was added to the diet of 12.78 kg piglets. The CuZn-SOD activity of whole blood at 15, 30 and 45 days was increased by 59.79% (17.48%) compared with the control group (containment copper 4.36 mg/kg). ), 25.90% (16.00%) and 19.02% (6.12%) (P<0.01) (Jiang Yibing, 1994). (3) Stimulate the activity of participating in growth hormone (factor) synthesis and secretion of enzymes, and increase the activity of these hormones (factors) in the body. Sorenson (1987) reported [9] that peptidyl α-amide monooxygenase is a copper-dependent enzyme necessary for the synthesis of neuroendocrine peptide hormones (such as thalamic release factor and anterior pituitary promoting hormone). However, reports on the above-mentioned areas of pigs are rarely seen.

Luo and Dove (1996) first discovered [15] that 250 mg/kg of copper sulfate was added, which significantly increased the intestinal lipase of weaned piglets (50.1 vs. 41.0 active units/g, P<0.01) and phospholipids compared with the 5 mg/kg group. The activity of enzyme A (16.8 vs. 13.0 activity units/g, P < 0.05) had no effect on the activity of trypsin, chymotrypsin and amylase in the small intestine and pancreas in the pancreas. The lipase and phospholipase A in the small intestine are secreted by the pancreas. The levels of the two enzymes in the pancreas are not affected by copper. It is likely that the copper in the pancreas is very low (about 1 mg/kg of fresh base). It is not affected by the addition of copper to the diet. In vitro tests further confirmed that the addition of copper sulfate-derived Cu2+ to the water bath medium of the small intestine chyme supernatant fed with low copper diet (5 mg/kg) pigs tends to constantly stimulate the purified pancreatic lipase activity of pigs (linear effect, P <0.01). The increase in intestinal lipase and phosphatase A activity ultimately led to an increase in dietary fat digestibility in weaned piglets (75.00% versus 68.8%, P < 0.01). This is also a good explanation for the addition of 250 mg/kg reported by Dove [6,16], which significantly improves the digestion and utilization of dietary fat in weaned piglets. The increase in fat digestibility caused by the addition of high-dose copper can increase the absorption of essential fatty acids and fat-soluble vitamins, and affect other aspects of nutrient metabolism in the body, thereby promoting the growth of pigs. The above findings may be a new mechanism of action of high copper on pig growth. Appropriate Cu2+ concentration activates pepsin in vitro and increases protein hydrolysis [17], but whether it has the same effect in vivo has not been confirmed.

2.4 Copper and Growth Hormone System

Supplemental feeding to stimulate growth levels of copper can increase protein deposition in young pigs and increase leanness. The addition of 250 mg/kg copper to the diet had no effect on the apparent digestibility of nitrogen in weaned piglets (Lro's Dove, 1996); however, the apparent deposition rate of nitrogen was significantly increased (63.7% vs. 57.5%), suggesting that copper can be added through the protein. Improve nitrogen deposition in pigs by means other than digestion. Braude (1965) reported [18] that the addition of 250 mg/kg copper to the diet increased the apparent digestibility and deposition rate of nitrogen in young pigs. Increased porcine nitrogen deposition caused by the addition of copper and the ocular muscle area and longissimus dorsi of pigs fed high-copper diets as reported by Lucas et al. (1962), Casted and Bowland (1968), Zhou et al. [14] (1994a) The increase in weight is consistent.

The synthesis of proteins in animals is regulated by a range of growth-promoting hormones and related factors. Both intravenous and oral high-copper increased the activity of serum mitogens (splitting peptide hormones, an indicator of blood growth factor activity) in weaned piglets [11,14]. In vitro studies have shown that copper stimulates the secretion of bovine pituitary growth hormone (GH) [17], and copper can accumulate in the brain through the blood-brain barrier of pigs [14]. Therefore, copper stimulates related growth hormone (such as CH) and related factors (such as insulin-like growth factor-1, IGF-I. The main growth-promoting factor in the body, also known as endocrine-regulating polypeptide, the main function is to promote various types of cells Differentiation and DNA, RNA and protein synthesis in cells; plasma IGF-I concentration is maintained by pituitary GH regulating liver synthesis of IGF-I, while liver is the main site of copper storage in the body), promoting protein It is possible to synthesize and ultimately promote the growth of pigs. However, direct evidence in this regard is still needed from pigs.

Since the process of release of GH-promoting growth hormone into the bloodstream is dynamic and affected by many factors, it is difficult to directly determine the exact effect of copper on growth hormone in pigs. The development of modern molecular biology technology has made it possible to accurately study the effect of copper on the expression of growth hormone in pigs at the molecular level. However, no special research reports have been seen in this regard. Special explorations on this aspect at the molecular level are expected to have new discoveries and new results.

2.5 Copper participates in intestinal mucosal epithelial renewal and trophic generation

Miller (1992) reported that 6.60 kg of Yorkshire x Landrace pig F1 generation weaned pigs were fed corn-soybean whey diet, the test group was supplemented with 250 mg/kg of copper, and the 14-day test group and the control group were injected intraperitoneally with 3H. - Thymine, pigs were sacrificed at 1, 6, 12, 20, 32 and 44 h after injection, and duodenum, jejunum anterior segment, jejunum posterior segment, ileum, cecum and colon tissue samples were rapidly collected and assayed. The results showed that compared with the control group, the turnover rate of the anterior and posterior jejunum mucosa decreased to different degrees (P<0.10, P<0.05), and the cell generation interval of the jejunum was prolonged (P<0.05), thus slowing down the jejunum, etc. Organizations update speeds, thereby reducing their maintenance energy needs and correspondingly increasing the energy used for production.

Apgar (1994) pointed out that the addition of copper in the diet was 100-200 mg/kg, and the basal level of blood growth hormone secretion in pigs was significantly increased. Liu Guilin (1994) reported that 150,175 mg/kg copper was added to the diet, and α-globulin and β-globulin in the serum of piglets were significantly higher than those in the low copper group. Dietary copper supplementation 250mg/kg, net absorption of liver in portal vein of piglets was significantly reduced (P < 0.05).

3 Conclusion

Adding copper 62.5～250mg/kg to the feed can significantly promote the growth of piglets and reduce the consumption of unit weight gain. However, as the age of piglets increases, the effect of copper growth is weakened. The growth of copper in pigs may be related to the stimulation of pig feed intake, digestive enzyme activity and growth regulation hormone, indicating that the growth-promoting effect of copper is likely to be systemic; not just limited to the commonly considered gastrointestinal resistance Microbial action. The mechanism of action of copper growth requires more copper to be absorbed from the pig's intestine into the bloodstream and transported to the tissue cells for action. However, the most commonly used inorganic copper sulfate source in pig feed is not only easy to absorb moisture and agglomerate, it is inconvenient to process and store, it is easy to destroy vitamins, and the absorption rate is low, and the environment is polluted.

Piglets fed high-copper diet piglets were significantly darkened in color. Due to misleading by the merchants, the farmers believe that the pig feed intake is a good feed, which makes the use of high copper additives increase year by year. Since most of the copper in the feed is discharged from the feces, there are concerns that feeding high copper will inevitably lead to environmental pollution and damage the ecological balance. However, some people used pig manure to prepare lambs containing 30mg/kg or 60mg/kg of copper for feeding. Compared with lambs with the same copper concentration as copper, the former had lower liver copper storage. It shows that the utilization of copper in the feces is very low. There is currently no evidence that the consumption of high-copper feed pigs to excrete feces can lead to the destruction of ecological balance.

Although the research and practice to date have not found obvious environmental pollution problems caused by the use of high copper, in the long run, it cannot but attract people's attention. The latest research progress on the mechanism of copper growth promotion in pigs suggests that the development, development and application of high-efficiency new organic copper sources in pig production can maximize the effect of copper on pig growth and reduce the environmental pollution caused by copper discharge. Significance.