Copper as a nutrient, an antinutrient and antibacterial for poultry

Inclusion of copper in animal diets is common practice. Nevertheless, there are several factors to consider. An overview.


Inclusion of cop- per in animal di- ets is common practice in the industry.

opper was first shown to be an essential nutrient for sustaining haemoglobin levels, even though blood contains little copper. Interest in copper nutrition intensified in the 1930s when it was demonstrated

that certain diseases of cattle were shown to be due to a cop- per deficiency. These early studies led to extensive mapping of copper deficient areas around the globe and subsequently the use of copper in animal diets.

Copper requirement Copper requirements usually fall within the range of 4 – 8 ppm. Copper (Cu) can exist in three states of oxidation with two variants and so reactivity with other ions is inevitable but

variable. We can use this reactivity to develop “organic” forms of copper. The main function of Cu is as a cofactor in critical enzymes in blood and tissues. Deficiency signs range from anaemia to inadequate cartilage formation. While there is quite efficient recycling of Cu by the kidneys, there is poor re- cycling from bile and so bile is the main route for clearance when dietary supply exceeds demand. Very high copper levels are sometimes used as an antibacterial, where levels approach 25 – 40 x the normal requirement.

Sources and availability Copper sulphate is often the standard, although copper chlo- ride, oxide, and carbonate are also available commercially. Over the last few years two other issues have arisen which have refuelled interest in copper source and bioavailability. So called organic sources of copper, which are usually at- tached to amino or organic acids, have rekindled interest in the bio-efficacy of mineral supplements. The other more re- cent area of interest is consideration of the availability of min- erals such as copper in natural feed ingredients. Traditionally requirements for Cu are met entirely by supplements with no account of the mineral present in cereals and proteins. This recent interest stems from attempts to minimise the nutrient supply of Cu and other minerals as a means of reducing ma- nure levels and so addressing environmental concerns. While it is easy to measure total levels of Cu in major ingredients, measuring bioavailability is a complex procedure. A broiler starter diet will normally provide around 150% of the Cu requirement. However, the proportion that is available to the bird is variable due to farming conditions when grow- ing maize and soya and the prior nutritional status of animal proteins. Bioavailability will be affected by parameters used in estimation, which for Cu seem to range from simple pro- duction characteristics through to liver and bile accumulation indices. The bioavailability of Cu in wheat and maize seems to

▶ ALL ABOUT FEED | Volume 29, No. 5/6, 2021 15


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