IT DOES AFFECT THE GIZZARD
Copper Sulfate has been used for decades at 250ppm in piglets starter and grower diets as growth promoter. Several modes of action are proposed by scientists to explain the positive effect of high level of copper on animal growth but the main one is related to its antibacterial effect, easily demonstrated in-vitro. Copper Sulfate is less used in Poultry and we were looking for the reasons behind this difference of use.
The reduction of these bacteria load is actually reducing their degradation of nutrients in the small intestine and increase the availability of vital nutrients for the animals such as amino-acids and fat. Studies show that the addition of high level of copper in the diets (250ppm in Swine and 150ppm in Poultry) bring down the quantity of protein produced by bacteria in the ileum (called bacteria protein).
As result of a lower production of bacterial protein synthesis, there is an improvement of the Apparent Ileal Digestibility (AID) and Apparent Total Tract Digestibility (ATTD) as illustrated below, explained the better growth performance of the animals.
Apart from the antibacterial effect, some studies underlined as well the correlation between higher dose of copper with the augmented expression of genes involved in the post-digestive metabolism of lipids. These reasons partly explain why copper sulfate has been used successfully in Swine nutrition from piglets weaning diets up to grower and even sometimes finisher diets. An interesting point to note is that the growth promoting effect of copper seems to be additive to the growth promoting effect of zinc oxide and even antibiotics.
In Poultry, a meta-analysis of all publications on the subject brings unclear results. The copper sulfate is used at dosage from 75 up to 150ppm but growth promoting effect is not observed in all studies. When the challenge is limited, the differences between treatment and control is rarely observed. Copper sulfate seems to have a growth promoting effect only when the bacterial challenge on the birds is augmented.
Nevertheless, the antibacterial effect of copper is not to be questioned anymore, even for Poultry and is certainly contributing positively to the gut health of the birds and a nutrient sparing effect. The reasons why these growth promoting effects do not appear in all studies may actually come from some toxic factors that copper may have on Poultry.
We know, even in Swine, that high dosage of copper, especially copper sulfate can increase copper bioavailability and disturb homeostasis. With facing too high level of solubilized copper in the gut, the mechanism of regulating its absorption is overwhelmed and excess of copper are stored in liver which could lead to its dysfunction. Poultry is particularly sensitive to copper toxicity, apparently more than Swine.
Another negative effect of copper sulfate could be related to its effect on the gizzard. In his 2016 publication, Pr Bent Jensen from European Food Safety Authority made a literature review and reveal the correlation between the usage of 100ppm of Copper during 8 weeks and gizzard erosion in 84-week layers with some negative effects on egg quality.