Zinc is one of the trace elements necessary for animals. With the increasing awareness of zinc, the transport and action of zinc in animals has gradually been revealed. Zinc can not only participate in the synthesis and metabolism of various enzymes, nucleic acids and proteins in the body. It has an extremely important role in the absorption of carbohydrates, the metabolism of vitamin A, reproductive functions and endocrine functions, as well as the growth and development of animals and the entire life activities. For this reason, at the beginning of the 20th century, zinc was referred to as "the spark of life." What are the factors related to the absorption and utilization of zinc in animal body and the research on the role of zinc in animal body? This article is a summary of the two aspects!
1. Factors that affect the transport and absorption of zinc in animals.
1.1 Influence of zinc source. Different zinc sources have different absorption and utilization rates in animals and thus have different effects on animal performance. Chen Hongliang (2000) found that adding organic zinc to piglets diets can significantly increase the daily gain and daily feed intake of the piglets, and proposes that the total dietary zinc content is 100 mg/kg, and the organic zinc content accounts for 40 total zinc. % is best. Zhang et al. (2002) reported that organozinc is fast in animals and has high bioavailability. Not only does it prevent antagonism of other nutrients in the diet from affecting absorption, but also the daily gain of piglets is significantly higher than that of inorganics. Salt zinc. In addition, studies by hahn and Baker (1993) on pigs showed that zinc concentrations in pig plasma fed with zinc sulfate or organic zinc were significantly higher than those fed zinc oxide. However, according to Wang Minqi and Xu Zincong (2002), adding high-dose ZnO to the diet can increase the apparent digestibility of crude protein and crude fat of piglets by 11.35% (P<0.01) and 36.94% (P<0.01, respectively). ), but the high-dose zinc sulfate apparent digestibility of piglets also increased, but did not reach significant levels. Therefore, the absorption and utilization of organic zinc in animals is higher than inorganic zinc. Understanding of the effects and effects of inorganic zinc-zinc sulphate and zinc oxide on the feed efficiency of piglets has been reported so far. It has not yet been unified and needs further study.
1.2 Effects of feed types and absorption inhibitors on zinc. (1) The type of feed. According to Meyer 1983, solomons 1982 reported that zinc in animal feed is not only higher than zinc in plant feed, but also higher in animal body than vegetable feed. (2) The protein structure in the diet also affects the conversion of zinc in animals. Hill (1985) uses soy protein isolate as a substitute for ruminants, and the absorption and retention of zinc is significantly lower than that of the casein group. Soy protein replaces animal protein to reduce the absorption of the external standard 65zn (sandstrom1987a, grance1981). Among different amino acids, except that histidine has a promoting effect on zinc absorption when PH=7.5, the increase of cysteine, histidine, methionine, and tryptophan has no significant effect on zinc absorption. . (3) Factors affecting zinc absorption in feeds. Factors affecting zinc absorption in feeds include phytic acid, calcium, iron, copper and zinc. Likuski (1965) reported that adding 2% phytic acid to the semi-pure diet in weanling rats reduced zinc absorption. Experiments on chickens also yielded the same results (likuski1964, He Zhengfang 1993). However, it is surprising that fermented forage crops can reduce the phytic acid content and thus increase the zinc absorption rate (navert 1985). Calcium can impede zinc absorption and increase excretion. High calcium can slow the growth of chickens and reduce the conversion rate of feed, and adding a certain amount of zinc can not reduce the adverse effects of high calcium on chickens. Therefore, calcium has a certain influence on the absorption of zinc (huber1970, powell1967 Savage1964 and roberson1960). The interaction between iron and zinc is achieved by competing with endogenous ligands. Excessive iron affects the absorption of zinc (1981), while amino acids and small peptides promote zinc absorption. Wapnir (1983) and evans (1980). Campen (1969) performed ligation in situ in rats and injected copper and zinc into the ligated duodenum. The absorption of 65Zn was reduced, but when introduced by peritoneal injection, it did not affect the absorption of zinc by the duodenum. Copper interaction and rivalry take place in the absorption phase. Campen1966, storey1987 proved that excessive zinc affects copper intake and blood copper levels. In addition, Lowe (1997) reported that zinc sources affect the tissue copper concentration. In rats injected with zinc oxide and zinc sulfate, the copper concentration in kidney, muscle, and other tissues was lower than the methionine chelated zinc and zinc glycinate groups, which not only demonstrated the organic zinc The utilization rate in animals is high, and when the blood zinc concentration is too high, it also affects the absorption and utilization of copper. Zinc also has an effect on selenium enrichment. Liu Qinghua, et al. (2000) reported that under high zinc and selenium conditions, there is an interaction between zinc and selenium. A suitable amount of high zinc can prevent the toxic effects of high selenium on the body.
1.3 The storage of zinc in animals is different, and the absorption and utilization of zinc are also different. (smith 1978b, 1980) found that the zinc absorption rate in the small intestine of zinc deficiency rats was 627 nmol/h, compared with 229 nmol/h in normal rats. The sheep had a higher discharge of 46 mg/kg zinc compared to the 6 mg/kg group (miller 1966). Experiments by Zigler (1964), Miller (1967), Campen (1974), Pate (1970), Simth (1978), Coppen (1987), and Davies (1988) have shown that zinc-deficient animals have a high absorption rate for 65zn. The 65zn tissue retention rate is higher than that of the body zinc-good animals.
1.4 Influence of the pH environment of the digestive tract on zinc absorption. Tacnet (1993) showed that the absorption capacity of zinc was 17.8 nmol/min at pH 7.4 and 4.3 nmol/min and 2 nmol/min when pH was 6.65 and 5.96, respectively. Seal (1983) reported that at pH 7.3, the absorption of zinc by the duodenum was greatest in rats.
2. The role of zinc in animals and the effect of zinc deficiency on the body.
Zinc can participate in the synthesis and metabolism of various enzymes, nucleic acids and proteins in animals. It plays an extremely important role in the absorption of carbohydrates, the metabolism of vitamin A, reproductive function and endocrine function. In the absence of zinc, the activity of zincase is reduced, the metabolism of cystine and methionine is disordered, the inactivation of glutathione peptide peroxidase, the synthesis of DNA and RNA is reduced, the growth of cell division is blocked, the growth of animals is stagnated, and the weight gain is slow. Reduced viability and resistance to disease.
2.1 Zinc promotes the calcification of egg shells and the formation of egg contents. Zinc is a prosthetic group of carbonic anhydrase, which can influence the quality of egg shells by affecting the activity of carbonic anhydrase. Wedekind (1990, 1992) showed that the addition of 2 g/L sodium chloride to the laying water of 71-week-old laying hens reduced eggshell quality, but at the same time added 0.5 g/kg methionine zinc or zinc sulfate to the diet. Can significantly reduce the defects of the eggshell and improve the quality of the shell. However, most studies have shown that zinc can be beneficial to the calcification of eggshells and to the quality of eggshells only when added to the diet of layer chickens simultaneously with manganese (Holder, 1987; Huntly, 1978). Tahatapob (1985) conducted an in-depth study of the effects of zinc and manganese on eggshells, suggesting that 75 mg/kg of manganese and 50 mg/kg of zinc can result in higher calcium to nitrogen ratios and increased uronic acid content in eggs. The quality of the shell. In addition, it was pointed out that the addition of organic zinc and manganese to high-calcium diets has high bioavailability and has a significant effect on eggshells. Cao Shengfeng, et al. (2000) reported that zinc levels in eggs increased significantly when they were fed 60--1210 mg/kg zinc diet, but Chen Youliang et al. (2000) reported that layer chickens consumed 1000-3000 mg/kg zinc diets. Although the zinc content in eggs increased, the increase was modest.
2.2 Zinc can participate in the metabolism of carbohydrates, affecting the taste system of dairy cows. When zinc deficiency occurs, the animal's appetite decreases, feed intake decreases, and animal weight gain slows down. Wang Minqi and Xu Yurong studied the effect of high-dose inorganic zinc supplementation on the digestive performance of weaned piglets. Studies have shown that: When 3000 mg/kg ZnO was added to the diet, the apparent digestibility of crude protein and crude fat increased by 11.35% (P<0.01) and 36.94% (P<0.01), respectively; stomach and pancreas The relative weight of the small intestine increased by 20.00% (P<0.05), 20.57% (P<0.05), and 38.8% (P<0.01), respectively; total proteinase, trypsin, amylase, and fat of duodenal contents. The enzyme activity was increased by 6.97% (P<0.05), 25.37% (P<0.05), 41.86% (P<0.05), and 110.91% (P<0.01), respectively. In addition, 3000 mg/kg zinc oxide and zinc sulfate reduced the number of fecal E. coli by 50.38% (P<0.01) and 48.5% (P<0.01), and the frequency of diarrhea decreased by 96.88% (P<0.01) and 68.75% ( P<0.01).
2.3 Zinc can participate in hormone regulation and synthesis. Zinc can promote the synthesis of growth hormones and sex hormones, and participate in the regulation of body fluids. When zinc deficiency occurs, the synthesis of growth hormone and sex hormones is reduced, animals grow slowly, endocrine disorders occur and disorders occur. Zhao Baoyu and Gong Yuesheng reported that after one week's feeding of rats with zinc-deficient feed, the synthesis of growth hormone in the blood of rats decreased, and the concentration of sex hormones decreased by 20%. Zinc can affect sperm production, survival, development and the role of vitamin A through the gonadal gonadotropic gonadal pathway. In the absence of zinc, the libido of the public was reduced, the sperm survival rate was decreased, the female libido was cold, the egg development was incomplete, and the conception rate was reduced. The effects and functions of vitamin A cannot be exerted, and the structure of the lipid layer, mucous membrane layer, and cell membrane layer of the animal will be affected.
2.4 Zinc can participate in protein synthesis. In the absence of zinc, the synthesis of skin collagen is reduced, abnormal cross-linking of collagen in blood occurs, and epidermal keratinization occurs. Nervberne et al. (1978) found that dairy cows suffer from decreased milk production and milk quality due to lack of zinc, atrophy of testicles of bulls, chaotic cycle of cows, decreased fertility rate, and prone to premature birth abortions and fetal malformations. Yao Junhu et al. reported that the addition of 10.1 mg/kg of zinc to the diet can promote young cattle growth and feed utilization. Li Wenli et al. believe that adding zinc to diets can improve the quality of bull semen and promote the occurrence and maturation of sperm and the improvement of sperm freezing tolerance. The study also found that regular protein zinc supplementation not only reduced cow's internal infection in the breast, but also increased the calving rate and the pregnancy rate of young cows and adult cows.
Effects of zinc on animal tissues, their production performance and immune function. Yan Sumei, He Yongqing, etc. randomly divided 180 day-old Averm broilers into a control group and 5 test groups. A total of 30 males and females, 30 in each group, and the control group were fed a basal diet with a zinc level of 22.61 mg/kg. The experimental group was supplemented with 25, 65, 145, 305 and 625 mg/kg of zinc and zinc in the basal diet. The source was zinc sulfate. The effect of dietary zinc levels on tissue zinc concentration, production performance and immune function was studied. The results showed that there was no significant change in performance of broilers when they were fed a basal diet containing zinc at a concentration of 22.61 mg/kg. However, the zinc concentration in the liver and tibia was significantly reduced, and the humoral immunity and cellular immune function decreased to varying degrees, suggesting that the diet was lacking. Zinc, dietary levels in the range of 47.61-81.61mg/kg, broiler liver and tibia zinc concentration is relatively stable, performance-immune function are also high, suggesting that the amount of zinc in the diet must be appropriate. When the dietary zinc level was 167.61 mg/kg, the broilers had higher immune function but the zinc concentration in the liver and tibia had a corresponding abnormal change, and the production performance also showed a downward trend, indicating that the dietary critical zinc was excessive; the level of dietary zinc was high At 327.61 mg/kg, the zinc concentration in the liver and tibia of broiler chickens changed abnormally, and the immune function of production performance also decreased significantly, suggesting excessive dietary zinc. This shows that zinc is of great importance to animal tissue, production performance, and immune function.
3 The effect of zinc on the regulation of animal gene expression.
With the increasing awareness of zinc in animals, scientists have turned their gaze to the study of animal genes in zinc. This provides a scientific basis for animals to feed on specific economic goals and use values. Wide prospects for the extensive use of zinc in animal production have opened up. Ji Feng and Luo Xugang (2003) believe that zinc can participate in gene regulatory proteins. Zn2+ regulates gene-specific expression mainly through transcriptional regulation of gene regulatory proteins. At present, there are more than 500 Zn2+-related gene regulatory proteins found in various organisms, of which 5 have been proved. They are: transcription factor A (TflllA), glucocorticoid receptor (GR), estrogen receptor (estro-genrecptor, ER), GAL4 and gene32 protein (g32p), when using Zn2+ chelation After the mixture removes Zn2+ in the center of these gene regulatory proteins, their specific binding to DNA and the like is inhibited, and the structural stability of the protein itself is also destroyed, which affects the expression of the gene. The potential toxicity of zinc is low, and its bioavailability is high. Scientists have used this finding to start using zinc-regulated genes to meet production needs, which will have enormous social and economic benefits. It has been reported that the use of zinc-regulated genes has been successfully tested in pigs. The use of zinc trigger factor sequences integrated into the DNA sequence of the non-fat growth control gene of the pig's chromosomes will accelerate non-fat growth and increase carcass lean percentage. This will be particularly effective in improving the quality of meat and increasing the slaughter rate. The operation of this technique is very simple. That is, weeks before the pig is slaughtered, when the pig tends to store carcass fat, adding zinc to the feed to start the growth gene will promote the non-fat growth of the pig. Get a higher carcass lean rate.
Conclusion: With the development of molecular biology technology, the study of zinc in animals will be further deepened, but the theoretical depth is not the ultimate goal of our research, only the esoteric theory into something that is easy to grasp and operate, Directing production and practice is the ultimate requirement. Therefore, in the actual combination of scientific research and production, there is a need for a technical standard with strong pertinence, high accuracy, ease of quantification, and specific operation that can be applied to animals of different breeds, different age structures, and different physiological development periods. For people to master, so that science and technology truly become a reality of productivity. In addition, for the moment, most of the research results are obtained in mice experiments, and there are relatively few researches in livestock and poultry. We hope to strengthen the research in this area and make the research results more concrete and more realistic. , operability and pertinence.
1. Factors that affect the transport and absorption of zinc in animals.
1.1 Influence of zinc source. Different zinc sources have different absorption and utilization rates in animals and thus have different effects on animal performance. Chen Hongliang (2000) found that adding organic zinc to piglets diets can significantly increase the daily gain and daily feed intake of the piglets, and proposes that the total dietary zinc content is 100 mg/kg, and the organic zinc content accounts for 40 total zinc. % is best. Zhang et al. (2002) reported that organozinc is fast in animals and has high bioavailability. Not only does it prevent antagonism of other nutrients in the diet from affecting absorption, but also the daily gain of piglets is significantly higher than that of inorganics. Salt zinc. In addition, studies by hahn and Baker (1993) on pigs showed that zinc concentrations in pig plasma fed with zinc sulfate or organic zinc were significantly higher than those fed zinc oxide. However, according to Wang Minqi and Xu Zincong (2002), adding high-dose ZnO to the diet can increase the apparent digestibility of crude protein and crude fat of piglets by 11.35% (P<0.01) and 36.94% (P<0.01, respectively). ), but the high-dose zinc sulfate apparent digestibility of piglets also increased, but did not reach significant levels. Therefore, the absorption and utilization of organic zinc in animals is higher than inorganic zinc. Understanding of the effects and effects of inorganic zinc-zinc sulphate and zinc oxide on the feed efficiency of piglets has been reported so far. It has not yet been unified and needs further study.
1.2 Effects of feed types and absorption inhibitors on zinc. (1) The type of feed. According to Meyer 1983, solomons 1982 reported that zinc in animal feed is not only higher than zinc in plant feed, but also higher in animal body than vegetable feed. (2) The protein structure in the diet also affects the conversion of zinc in animals. Hill (1985) uses soy protein isolate as a substitute for ruminants, and the absorption and retention of zinc is significantly lower than that of the casein group. Soy protein replaces animal protein to reduce the absorption of the external standard 65zn (sandstrom1987a, grance1981). Among different amino acids, except that histidine has a promoting effect on zinc absorption when PH=7.5, the increase of cysteine, histidine, methionine, and tryptophan has no significant effect on zinc absorption. . (3) Factors affecting zinc absorption in feeds. Factors affecting zinc absorption in feeds include phytic acid, calcium, iron, copper and zinc. Likuski (1965) reported that adding 2% phytic acid to the semi-pure diet in weanling rats reduced zinc absorption. Experiments on chickens also yielded the same results (likuski1964, He Zhengfang 1993). However, it is surprising that fermented forage crops can reduce the phytic acid content and thus increase the zinc absorption rate (navert 1985). Calcium can impede zinc absorption and increase excretion. High calcium can slow the growth of chickens and reduce the conversion rate of feed, and adding a certain amount of zinc can not reduce the adverse effects of high calcium on chickens. Therefore, calcium has a certain influence on the absorption of zinc (huber1970, powell1967 Savage1964 and roberson1960). The interaction between iron and zinc is achieved by competing with endogenous ligands. Excessive iron affects the absorption of zinc (1981), while amino acids and small peptides promote zinc absorption. Wapnir (1983) and evans (1980). Campen (1969) performed ligation in situ in rats and injected copper and zinc into the ligated duodenum. The absorption of 65Zn was reduced, but when introduced by peritoneal injection, it did not affect the absorption of zinc by the duodenum. Copper interaction and rivalry take place in the absorption phase. Campen1966, storey1987 proved that excessive zinc affects copper intake and blood copper levels. In addition, Lowe (1997) reported that zinc sources affect the tissue copper concentration. In rats injected with zinc oxide and zinc sulfate, the copper concentration in kidney, muscle, and other tissues was lower than the methionine chelated zinc and zinc glycinate groups, which not only demonstrated the organic zinc The utilization rate in animals is high, and when the blood zinc concentration is too high, it also affects the absorption and utilization of copper. Zinc also has an effect on selenium enrichment. Liu Qinghua, et al. (2000) reported that under high zinc and selenium conditions, there is an interaction between zinc and selenium. A suitable amount of high zinc can prevent the toxic effects of high selenium on the body.
1.3 The storage of zinc in animals is different, and the absorption and utilization of zinc are also different. (smith 1978b, 1980) found that the zinc absorption rate in the small intestine of zinc deficiency rats was 627 nmol/h, compared with 229 nmol/h in normal rats. The sheep had a higher discharge of 46 mg/kg zinc compared to the 6 mg/kg group (miller 1966). Experiments by Zigler (1964), Miller (1967), Campen (1974), Pate (1970), Simth (1978), Coppen (1987), and Davies (1988) have shown that zinc-deficient animals have a high absorption rate for 65zn. The 65zn tissue retention rate is higher than that of the body zinc-good animals.
1.4 Influence of the pH environment of the digestive tract on zinc absorption. Tacnet (1993) showed that the absorption capacity of zinc was 17.8 nmol/min at pH 7.4 and 4.3 nmol/min and 2 nmol/min when pH was 6.65 and 5.96, respectively. Seal (1983) reported that at pH 7.3, the absorption of zinc by the duodenum was greatest in rats.
2. The role of zinc in animals and the effect of zinc deficiency on the body.
Zinc can participate in the synthesis and metabolism of various enzymes, nucleic acids and proteins in animals. It plays an extremely important role in the absorption of carbohydrates, the metabolism of vitamin A, reproductive function and endocrine function. In the absence of zinc, the activity of zincase is reduced, the metabolism of cystine and methionine is disordered, the inactivation of glutathione peptide peroxidase, the synthesis of DNA and RNA is reduced, the growth of cell division is blocked, the growth of animals is stagnated, and the weight gain is slow. Reduced viability and resistance to disease.
2.1 Zinc promotes the calcification of egg shells and the formation of egg contents. Zinc is a prosthetic group of carbonic anhydrase, which can influence the quality of egg shells by affecting the activity of carbonic anhydrase. Wedekind (1990, 1992) showed that the addition of 2 g/L sodium chloride to the laying water of 71-week-old laying hens reduced eggshell quality, but at the same time added 0.5 g/kg methionine zinc or zinc sulfate to the diet. Can significantly reduce the defects of the eggshell and improve the quality of the shell. However, most studies have shown that zinc can be beneficial to the calcification of eggshells and to the quality of eggshells only when added to the diet of layer chickens simultaneously with manganese (Holder, 1987; Huntly, 1978). Tahatapob (1985) conducted an in-depth study of the effects of zinc and manganese on eggshells, suggesting that 75 mg/kg of manganese and 50 mg/kg of zinc can result in higher calcium to nitrogen ratios and increased uronic acid content in eggs. The quality of the shell. In addition, it was pointed out that the addition of organic zinc and manganese to high-calcium diets has high bioavailability and has a significant effect on eggshells. Cao Shengfeng, et al. (2000) reported that zinc levels in eggs increased significantly when they were fed 60--1210 mg/kg zinc diet, but Chen Youliang et al. (2000) reported that layer chickens consumed 1000-3000 mg/kg zinc diets. Although the zinc content in eggs increased, the increase was modest.
2.2 Zinc can participate in the metabolism of carbohydrates, affecting the taste system of dairy cows. When zinc deficiency occurs, the animal's appetite decreases, feed intake decreases, and animal weight gain slows down. Wang Minqi and Xu Yurong studied the effect of high-dose inorganic zinc supplementation on the digestive performance of weaned piglets. Studies have shown that: When 3000 mg/kg ZnO was added to the diet, the apparent digestibility of crude protein and crude fat increased by 11.35% (P<0.01) and 36.94% (P<0.01), respectively; stomach and pancreas The relative weight of the small intestine increased by 20.00% (P<0.05), 20.57% (P<0.05), and 38.8% (P<0.01), respectively; total proteinase, trypsin, amylase, and fat of duodenal contents. The enzyme activity was increased by 6.97% (P<0.05), 25.37% (P<0.05), 41.86% (P<0.05), and 110.91% (P<0.01), respectively. In addition, 3000 mg/kg zinc oxide and zinc sulfate reduced the number of fecal E. coli by 50.38% (P<0.01) and 48.5% (P<0.01), and the frequency of diarrhea decreased by 96.88% (P<0.01) and 68.75% ( P<0.01).
2.3 Zinc can participate in hormone regulation and synthesis. Zinc can promote the synthesis of growth hormones and sex hormones, and participate in the regulation of body fluids. When zinc deficiency occurs, the synthesis of growth hormone and sex hormones is reduced, animals grow slowly, endocrine disorders occur and disorders occur. Zhao Baoyu and Gong Yuesheng reported that after one week's feeding of rats with zinc-deficient feed, the synthesis of growth hormone in the blood of rats decreased, and the concentration of sex hormones decreased by 20%. Zinc can affect sperm production, survival, development and the role of vitamin A through the gonadal gonadotropic gonadal pathway. In the absence of zinc, the libido of the public was reduced, the sperm survival rate was decreased, the female libido was cold, the egg development was incomplete, and the conception rate was reduced. The effects and functions of vitamin A cannot be exerted, and the structure of the lipid layer, mucous membrane layer, and cell membrane layer of the animal will be affected.
2.4 Zinc can participate in protein synthesis. In the absence of zinc, the synthesis of skin collagen is reduced, abnormal cross-linking of collagen in blood occurs, and epidermal keratinization occurs. Nervberne et al. (1978) found that dairy cows suffer from decreased milk production and milk quality due to lack of zinc, atrophy of testicles of bulls, chaotic cycle of cows, decreased fertility rate, and prone to premature birth abortions and fetal malformations. Yao Junhu et al. reported that the addition of 10.1 mg/kg of zinc to the diet can promote young cattle growth and feed utilization. Li Wenli et al. believe that adding zinc to diets can improve the quality of bull semen and promote the occurrence and maturation of sperm and the improvement of sperm freezing tolerance. The study also found that regular protein zinc supplementation not only reduced cow's internal infection in the breast, but also increased the calving rate and the pregnancy rate of young cows and adult cows.
Effects of zinc on animal tissues, their production performance and immune function. Yan Sumei, He Yongqing, etc. randomly divided 180 day-old Averm broilers into a control group and 5 test groups. A total of 30 males and females, 30 in each group, and the control group were fed a basal diet with a zinc level of 22.61 mg/kg. The experimental group was supplemented with 25, 65, 145, 305 and 625 mg/kg of zinc and zinc in the basal diet. The source was zinc sulfate. The effect of dietary zinc levels on tissue zinc concentration, production performance and immune function was studied. The results showed that there was no significant change in performance of broilers when they were fed a basal diet containing zinc at a concentration of 22.61 mg/kg. However, the zinc concentration in the liver and tibia was significantly reduced, and the humoral immunity and cellular immune function decreased to varying degrees, suggesting that the diet was lacking. Zinc, dietary levels in the range of 47.61-81.61mg/kg, broiler liver and tibia zinc concentration is relatively stable, performance-immune function are also high, suggesting that the amount of zinc in the diet must be appropriate. When the dietary zinc level was 167.61 mg/kg, the broilers had higher immune function but the zinc concentration in the liver and tibia had a corresponding abnormal change, and the production performance also showed a downward trend, indicating that the dietary critical zinc was excessive; the level of dietary zinc was high At 327.61 mg/kg, the zinc concentration in the liver and tibia of broiler chickens changed abnormally, and the immune function of production performance also decreased significantly, suggesting excessive dietary zinc. This shows that zinc is of great importance to animal tissue, production performance, and immune function.
3 The effect of zinc on the regulation of animal gene expression.
With the increasing awareness of zinc in animals, scientists have turned their gaze to the study of animal genes in zinc. This provides a scientific basis for animals to feed on specific economic goals and use values. Wide prospects for the extensive use of zinc in animal production have opened up. Ji Feng and Luo Xugang (2003) believe that zinc can participate in gene regulatory proteins. Zn2+ regulates gene-specific expression mainly through transcriptional regulation of gene regulatory proteins. At present, there are more than 500 Zn2+-related gene regulatory proteins found in various organisms, of which 5 have been proved. They are: transcription factor A (TflllA), glucocorticoid receptor (GR), estrogen receptor (estro-genrecptor, ER), GAL4 and gene32 protein (g32p), when using Zn2+ chelation After the mixture removes Zn2+ in the center of these gene regulatory proteins, their specific binding to DNA and the like is inhibited, and the structural stability of the protein itself is also destroyed, which affects the expression of the gene. The potential toxicity of zinc is low, and its bioavailability is high. Scientists have used this finding to start using zinc-regulated genes to meet production needs, which will have enormous social and economic benefits. It has been reported that the use of zinc-regulated genes has been successfully tested in pigs. The use of zinc trigger factor sequences integrated into the DNA sequence of the non-fat growth control gene of the pig's chromosomes will accelerate non-fat growth and increase carcass lean percentage. This will be particularly effective in improving the quality of meat and increasing the slaughter rate. The operation of this technique is very simple. That is, weeks before the pig is slaughtered, when the pig tends to store carcass fat, adding zinc to the feed to start the growth gene will promote the non-fat growth of the pig. Get a higher carcass lean rate.
Conclusion: With the development of molecular biology technology, the study of zinc in animals will be further deepened, but the theoretical depth is not the ultimate goal of our research, only the esoteric theory into something that is easy to grasp and operate, Directing production and practice is the ultimate requirement. Therefore, in the actual combination of scientific research and production, there is a need for a technical standard with strong pertinence, high accuracy, ease of quantification, and specific operation that can be applied to animals of different breeds, different age structures, and different physiological development periods. For people to master, so that science and technology truly become a reality of productivity. In addition, for the moment, most of the research results are obtained in mice experiments, and there are relatively few researches in livestock and poultry. We hope to strengthen the research in this area and make the research results more concrete and more realistic. , operability and pertinence.