Abstract: This article reviews the experimental data of trace element nutrition research and the application of organic trace elements in broilers, focusing on copper, iron, manganese, zinc and other trace elements. With the increasing growth of broilers and the bioavailability of organic trace elements, it is necessary to reassess the nutritional needs of broilers for copper, iron, manganese and zinc. For broilers, zinc is a key trace element. Although the content of zinc in the tissue remains relatively constant, the lack of zinc can seriously affect the feed intake, which in turn affects the growth of broilers. Based on the study of the semi-purified diet method, including the zinc content in the basal diet, the zinc requirement for broilers was as follows: 60 mg/kg for 0-14 days and 70 mg/kg for 14 days. However, in the case where the supply of zinc is sufficient, it is difficult to determine the amount of organic copper, iron, and manganese required, because the zinc supply is sufficient, and the animal is less likely to exhibit the lack of symptoms of the above elements. For the modern broiler industry, comparative studies of organic traces and inorganic infinite quantities are not enough.
Foreword
At present, the study of mineral elements is mainly based on their economic value and the actual lack of feed (NRC 1994). Therefore, more research focuses on the calcium and phosphorus requirements of broilers, while the study of trace elements is far. It fell behind. In the batch or premix, the addition cost of inorganic copper, iron, manganese and zinc is low. Although these trace elements play an important role in broiler digestion, physiology, biosynthesis, and body growth, their demand in commercial diets has not been accurately determined for chicks and chickens older than 3 weeks of age. The amount of trace element required is also only a hypothetical value.
At present, 35-day-old broilers can weigh up to 2 kg, and between 21 and 35 days of age, broilers can gain 1 kg. The trace element requirement data reported by NRC is based only on the research results of the 1950s, because the genetic characteristics and feed ingredients of broilers have changed, both of which affect the demand for trace elements.
In other words, the low price and high density of the feeding environment of inorganic trace elements make the use of trace elements in the feed to ensure the absorption of trace elements. It can be concluded that the availability of trace elements in the diet and other components that affect their absorption and metabolism will influence the animal's demand for trace elements. In commercial practice, high doses of added inorganic trace elements will result in significant excretion. Excreta will affect the physiological status of water sources and plants. For example, under commercial conditions, 94% of undigested zinc is excreted by broilers (Mohanna and Nys 1999). Feeding the dung peas to the dung peas, 90mg / kg zinc feed feed large poultry and 360 mg / kg zinc feed feed large poultry manure for comparative study, crop yield per hectare will be reduced from 876 kg to 90 mg /kg (Giordano et al. 1975). Therefore, we have reason to reduce the amount of trace elements or increase their utilization. However, the content of trace elements in different feed ingredients is not the same, and the interaction between trace elements will also lead to changes in their utilization.
1, trace elements and broiler feeding regulation
1.1 Feed control
Studies have found that the reduction in dietary zinc levels is always accompanied by a decrease in feed intake and growth retardation. If the inorganic or organic zinc in the diet is restricted, the feed intake will decrease and the growth rate will be blocked at 21 days of age (Bao et al. 2009).
1.2 Hormone regulation
Cholecystokinin (CCK) is a peptide hormone that is stimulated by semi-digested food to stimulate intestinal mucosal cells to control gastric emptying and feeding (Reidelberger 1994). Recent studies have found that zinc deficiency up-regulates CCK gene expression (Bao 2007), suggesting that CCK is regulated by feed intake rather than zinc metabolism itself.
2, the absorption and excretion of trace elements
At present, the trace elements of broilers are mainly from three parts: drinking water; food ingredients and added inorganic or organic trace elements. Under normal circumstances, drinking water is the main source of mineral elements in broilers, but the amount of water consumed by individuals varies widely and cannot be used to accurately calculate trace elements obtained from water (Underwood 1999). The content of trace elements in broiler feed ingredients varies widely, and there is little data on the utilization of mineral elements in feed ingredients. Mineral elements absorbed by broilers usually only consider mineral salts added from the feed. The content of mineral elements in different feed ingredients has fluctuated greatly, as shown in Table 3 (AW-Young et al. 1983)
The apparent utilization of copper, iron, manganese and zinc is low. The absorption of copper is mainly in the duodenum (Underwood and Suttle, 1999
There are two types of organic iron, blood iron and non-blood iron (Henry 1995a). a. Non-blood iron is mainly found in plants, and its solubility in the upper part of the small intestine strongly affects its absorption efficiency (Yip and Dallman 1996). Factors affecting non-blood iron absorption in diets include Ca, P, bran and phytic acid. However, the addition of a relatively small amount of Vc to the diet increases the absorption of non-blood iron. b. Blood iron is mainly derived from hemoglobin and myoglobin in the muscle, and its absorption is less affected by other components of the diet.
The absorption of manganese runs through the entire intestine, and no reports indicate that the level of manganese in the diet affects the absorption of other trace elements (Keen and Zidenberg-Cherr 1996).
The absorption of zinc can be physiologically divided into two stages: zinc enters the cell from the intestinal lumen; from the cell to the circulatory system (Swinkels et al. 1994). The absorption position of zinc is not exact. Most people think that zinc is absorbed in the small intestine, mainly the duodenum and jejunum, and the ileum is also involved in absorption. Current research indicates that the main absorption site of zinc is the ileum, and the absorption rate of organic zinc in the ileum is higher than that of inorganic zinc (Bao et al. 2007).
Copper, iron, manganese and zinc are acid soluble and susceptible to hydroxyl polymerization (Powell et al. 1999). In the environment where the intestines approach neutrality, they tend to form insoluble hydroxide precipitates. Therefore, the absorption of these trace elements may be controlled by the gastric acid secretion. A decrease in gastric acid secretion may result in a decrease in the availability of soluble, potentially available trace element metals in the intestine.
The gastrointestinal tract (GIT) is the main excretion site for copper, iron, manganese and zinc. Urine is the main route of excretion of elements such as magnesium, iodine and potassium (Ammerman 1995). The excreted mineral elements mainly include three types: minerals that cannot be absorbed, elements produced by endogenous cell wear, and excessive amounts of unabsorbed elements. Feeding excessive amounts of trace elements often leads to underestimation of the potential bioavailability of trace elements (Underwood and Suttle 1999).
3, the amount of trace elements required for broilers and factors affecting the utilization of trace elements
3.1 Trace element requirements
The copper level required for broilers to reach maximum growth weight is 9 mg/kg. When the body weight, hemoglobin concentration and blood cell volume were used as the indicators, the iron requirement in the diet was 79, 77.7, 77 mg/kg, respectively. Davis et al. (1968) used soybean meal containing 19 mg/kg as the base diet alone and found that the iron concentration at the body weight reference point was 79 mg/kg. Vahl and Van'Tklooster (1986) concluded that previous studies indicated that the dietary iron concentration should be 100 mg/kg (including iron in the feedstock). Vahl and Van'Tklooster (1986) used a conventional diet with an iron concentration of 80 mg/kg, and slowly added a certain amount of inorganic iron until the iron concentration was 1620 mg/kg. After adding 20-60 mg/kg, the weight gain was observed. That is to reach the platform period.
There is a lot of information on the zinc requirement of broilers, which is mainly determined by semi-homogenous diets, generally 35~40mg/kg (NRC 1994). Batal et al. (2001) used a semi-homogenous diet to add 0, 5.81, 10.81, 15.1, and 20.25 mg/kg zinc sulfate, respectively, and found that the broiler weight increased linearly at the first three levels. In recent years, it has been reported that the addition of 80mg/kg or 110mg/kg zinc-containing diets can ensure the ideal growth of broilers, but in the first 3 weeks of broiler feeding, the basal diet (containing 30mg/kg of zinc) and added There was no significant difference in broiler growth between zinc diets (Burrell et al. 2004). Based on the semi-purified control diet, the zinc content in the broiler diet was calculated as 58 mg/kg for the first 14 days and 68 mg/kg for 14-35 days (Bao et al. 2009).
The work of manganese requirements for broilers was mainly carried out by Gallup and Norris (1939). They used semi-homogeneous diets to control manganese concentrations from 20 mg/kg to 1000 mg/kg. It was found that at 50 mg/kg, the “manganese deficiency syndrome†was obvious. Reduced and significant growth response, but data on feeding efficiency were not reported. In addition, studies have indicated that additional manganese is not present in the diet with a manganese content of 37.5 mg/kg (Gardiner 1972).
Currently, commercial trace element addition levels are much higher than those recommended by NRC (1994). The following data is NRC recommendations and commercial recommendations (Teeter and Wiernus 2003).
It is not clear whether excess trace elements provide additional benefits. The need for these organic trace elements in broilers needs to be redefined. The main problem currently determining the amount of trace elements required for broilers is the rational preparation of semi-homogenous control diets.
3.2 Factors Affecting the Utilization of Trace Elements
Day age: The utilization rate of zinc decreased with age. It may be due to the increase in feed intake of adult animals and sufficient trace elements; it may also be due to the lack of maturity of biliary function in young animals, resulting in reduced endogenous zinc excretion.
Dietary crude protein content: Dietary high protein significantly increased the apparent absorption of zinc and deposition in bone (Snedeker and Greger 1983). However, diets fed high protein did not reduce the zinc requirement of animals (Hunt and Johnson 1992).
Dietary Calcium and Phosphorus Content: When zinc is added to pig diets, it increases calcium retention but does not increase phosphorus retention; diets do not increase zinc retention when increased calcium (Morgan et al. 1969).
Environmental factors: high temperatures increase the excretion of mineral elements (El-Husseiny and Creger 1981; Belay et al. 1992). Under heat stress, organic manganese significantly increased the manganese concentration in the tibia and showed a higher bioavailability than manganese sulfate (Smith et al. 1995).
4, the interaction between trace elements
Underwood and Suttle (1999) describe the interaction types of three trace elements:
1 different ions form a complex that cannot be absorbed in the intestine;
2 competitive metabolic pathway between similar ions;
3 induces non-specific metal binding proteins.
Although organic trace elements can be unaffected by phytic acid or other dietary components, similar trace element ions compete for transport systems and metabolic pathways.
Currently, the most common iron and copper ratio in the diet is 10:1. The absorption of iron does not affect the absorption of copper, but the absorption of iron in the absence of copper in the diet is significantly reduced (Schwartz and Kirchgessner 1974). Excess copper will significantly inhibit zinc absorption (O'Dell 1984). Excess zinc in the diet also affects copper absorption, which leads to anemia. Copper is quite sensitive to the uptake of zinc. Both copper and zinc uptake and absorption efficiency are enhanced when reducing dietary zinc supply (Cousins ​​1985). Excess manganese in the diet reduces hemoglobin concentration (Baker and Halpin 1991). So far, there has been no report of the interaction between zinc and manganese.
5, organic trace elements
5.1 Define
Ammerman et al. (1998) summarized several forms of organic complex trace elements according to the data of the American Association of Feed Control Officials: 1. The soluble metal salts and amino acids react in a certain molar ratio (from 1:1 to 1:3). a metal amino acid chelate. 2. A metal amino acid complex produced by the combination of a soluble salt and an amino acid. 3. A metal protein salt formed by the chelation of a soluble salt with an amino acid or a hydrolyzed protein. 4. A metal polysaccharide complex formed by mixing a soluble salt and a polysaccharide.
5.2 Characteristics of adding organic trace elements
Good stability; high bioavailability; low toxicity, less pollution, and good palatability. Adding organic or inorganic zinc can promote feeding, increase body weight, increase G:F value, and increase zinc concentration in liver and tibia. The ability of organic zinc to increase tissue zinc concentration is better than inorganic zinc (T. Ao et al. 2009).
5.3 Development History of Organic Trace Elements
As early as 1965, it was found that the addition of chelating agents to the diet could increase the utilization of zinc in soybean meal. It was found that the liver extract containing 1.5 mg/kg of zinc was added to the broiler diet with a zinc concentration of 10 mg/kg, and the growth effect was the same as that of the diet zinc concentration of 60 mg/kg ( Scott and Zeigler 1963). ). However, in this trial, broilers weighed only 500g at 4 weeks. Therefore, it is not known whether a zinc-containing diet of 11.5 mg/kg can meet the needs, or whether the liver extract improves the utilization efficiency of zinc. In 1972, zinc in corn was found to be 40% more efficient at increasing tissue zinc levels than direct addition of inorganic zinc (Patton 1997). Since then, there have been more than 100 articles on the efficiency of the use of organic trace elements, which suggest that not all organic trace elements have an advantage over inorganic minerals. After 1990, much research has focused on the growth of organic trace elements in broilers and other animals. The results show that only a proper amount of organic trace elements can be added to the broiler to meet the growth needs. Such a practice can save resources while reducing environmental pollution.
5.4 Application of Organic Trace Elements
From an economic and environmental point of view, it is necessary to reduce the level of trace elements in the diet to the point where it is necessary to minimize the amount of excretion (Thompson and Fowler 1990). Organic compound trace elements can absorb and utilize better than inorganic minerals while ensuring the growth of broilers.
Summary
As the growth rate of broilers increases and the utilization of trace elements increases, the need for Cu, Fe, Mn and Zn in broilers needs to be redefined. Zinc is one of the most important trace elements required for chickens. It maintains a relatively stable concentration in the tissue, and zinc deficiency in the diet can seriously affect feed intake and hinder the growth of broilers. The proposed literature has a wide range of variations on the recommended amount of zinc. Based on the semi-conventional diet, it can be reasonably estimated that the total zinc requirement for broilers is 60 mg/kg for the first 14 days and 70 mg/kg for 14 days, including zinc in the basal diet. In the case of sufficient zinc, the symptoms of other trace elements (Cu, Fe, and Mn) are not reflected in growth. At present, the data on the demand for various mineral elements in chickens are mostly realized through the basic diet, and there are still defects. Therefore, future trials need to develop semi-homogeneous diets.
The development prospect of organic trace elements is good, and it has broad application prospects for reducing environmental pollution. However, the rational application of organic trace elements remains to be further studied. At present, there are some problems in the application of organic trace elements: the absorption mechanism and metabolic principle of organic trace elements are not fully understood, and the beneficial effects on the performance of broiler chickens need more experiments to support, further research is needed to develop better additives. Provide theoretical basis; organic trace element production process needs to be improved to save costs and reduce market prices.
Solar Light outdoor flood led ,Solar Floodlight,Solar Garden Light,Solar Street Light
Shenzhen You&My Electronic Technology Co., Ltd , https://www.szyoumy.com