Now a days usage of copper in poultry diet is common practice. However, there are many factors to study.
Copper is an essential trace mineral for livestock and poultry. Copper as nutrient got seekers attention first time when it was known for maintaining haemoglobin levels, even copper is little bit present in blood. However in animals it got more importance in 1930s when it was reveled that copper deficiency is cause of certain diseases in cattle. Further studies regarding copper deficiency extended to mapping of areas around the world which were deficient in copper and then copper was added in the normal diet of animals.
Requirement of Copper
Normal range of copper is 4-8 ppm. Copper can exist in 3 oxidation states with different (2) variants and its reactivity with other ions is unavoidable but it is variable. we can develop "organic" form of copper by using this reactivity. Copper acts as cofactor (also known as cuproenzymes) in for different enzymes in body (blood & tissue). For example copper is a precursor of Beta-monoxygenase, which catalyzes the hydroxylation of dopamine to norepinephrine which is required for the production of GnrH. Supplementation of cu in laying hens diet is mainly for the change in the lipid profile of eggs. There is an efficient recycling of copper by kidneys, however when dietary supply increases from requirement then bile is the use to clear the excess amount of copper because bile is poor source of recycling. If copper increases from normal requirement up to 40 times then it can be used as antibacterial.
Cu deficiency sign & symptoms
Copper deficiency in poultry leads to severe health problems including growth depression, bone disability, poor feathering, anemia, rupture of aorta, failure of synthesize desmosine the cross link precursor of elastin. failure of lysine incorporation into desmosine molecule.
Source of Copper
Copper sulphate is often used as standard, although chloride, carbonate and oxide form is also commercially available but theses are inorganic form of copper. From last few years different issues have arisen which have again increased the interest of scientists regarding its source and bioavailability. Inorganic copper is less bioavailable as compared to organic copper. Usually amino acid (Glycine, Methionine, MHA and soy protein) or organic acids (Propionic acid) attached copper termed as organic source of copper have revived the bio-efficacy of mineral supplementation
Availability of Copper
Conventionally copper requirement is entirely met by supplements with no amount of minerals present in cereals and proteins. New study is mainly focusing on the availability of minerals such as Cu in natural feed ingredients. Scientist are trying to reduce the supply of Cu and other minerals in manure level and environmental pollution. Measuring total level of copper in major ingredients is easy however, measurement of mineral bioavailability is a complex procedure.
Copper Bioavailability
Bioavailability of copper in natural feed ingredients varies with ingredient wise. the bioavailability of Cu in wheat and maize is near to 80% while 40% to soybean meal. This low percentage of bioavailability of Cu might be due to binding with phytate. Bioavailability of Cu in these ingredients can be increased by using phytase in diet. CuSO4 and CuO are conventional source of copper, although bioavailability values depend on numerous factors around 65-75% on an average. Tribasic copper chloride in now a days available in market due to its non-hygroscopicity.
Organic Copper efficacy
Normally termed organic copper based products are combined with Lysine, Methionine, Glycine and soybean proteins. It is normally claimed that this type of minerals are differently absorbed and metabolised and also provide less opportunity for interference with other trace minerals.
Inorganic Copper Toxicity
when copper level increases 100 times from normal toxicity occurs. First, copper accumulates in the liver, but when copper level reach 25 times from normal, then Cu enters into the circulation and starts destructing RBCs. No natural feed ingredient is sufficient high in Cu to cause toxicity.
Mineral Interactions
Copper, zinc, iron and molybdenum interaction is classical example of mineral interaction. Major portion of copper is absorbed from the duodenum because zinc also attached to the same mucosal carrier, high level of dietary zinc cause competition, leading to deficiency of copper, however it is difficult to diagnose, since the diet contains normal level of copper. Commercial use of pharmacological level of diet Cu for growth promotion in meat birds has been questioned in terms of compatibility with Phytase enzymes. Rich level of dietary Cu result in reduced solubility of phytic acid, which effect enzyme activity. There has been some debate regarding impact of high level of Cu requirement for certain amino acids. Chicks growth depressed by feeding up to 700 mg/kg dietary Cu is alleviated by adding extra DL-methionine. It is common practice to add extra methionine during usage of commercial copper level.
Copper impact on cholesterol metabolism
Normally high level of Cu in diet has consistent effect on reducing egg Cholesterol level. Feeding Cu up to 250 ppm has been reported to reduce egg cholesterol by up to 25% meat in broilers. Consistent use of Cu to reduce egg cholesterol is that >95% is excreted in the manure.
Copper as an antibacterial
Still high level of copper is used as growth promoter, at 250 mg/kg diet, though the accumulation of Cu in manure leads to the legislative restrictions. Due to addition of dietary Cu level in diet the color of bird manure changes significantly, and change in gut microflora is also assumed. It is noticed that feeding commercial level of Cu may have beneficial effect up to 15% improved digestion in haemicellulose. The utter most results of high level copper feeding can be seem to occur after 2-3 flocks have been grown on reused litter, implying the change in microbial status of litter. Increase in Cu level in manure increases the soil Cu. High level of manure Cu suppress microbial uricase activity, limiting ammonia release.
Conclusion
The minimum requirement of Cu for poultry is around 5-8 mg/kg. Success with low levels of supplemental Cu (2-3 mg/kg) seem predicated on proportional reduction of all trace minerals and not Cu in isolation. when lower level of Cu is considered as a mean of reducing environmental pollution, then the bioavailability of Cu in traditional diet ingredients need to be considered. If there is requirement of reducing Cu level in manure, then there needs to be examined bioavailability of Cu in major feed ingredients used worldwide. Normally >90% Cu consumed appears in the manure, where soil accumulation is less problematic than the potential leaching of Cu into watercourses.
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