Gut Health of Broilers in Response to Different Sources and Levels of Copper

Copper (Cu) is a vital element involved in cellular metabolism and enzyme systems. At levels greater than nutritional requirements, dietary Cu addition enhances growth performance as a growth promoter (Pesti and Bakalii, 1996). Copper dosing at levels up to 250 mg/kg feed has been shown to improve intestinal structure and function, and alter the intestinal microbiota profile (Di Giancamillo et al., 2018). However, a high level of copper in the sulphate form (CuSO₄) which is chemically reactive, may irritate the gut lining and oxidize fat and other nutrients. Copper in the hydroxychloride form (CH) is comparatively less soluble and reactive than CuSO₄at neutral pH, and presents higher bioavailability.

This study aimed to compare the effects of nutritional and growth-promoting dose of CH with CuSO₄, by examining intestinal morphology, caecal microbiota population, and jejunal gene expression. Ross 308 male day-old chicks (n = 864) were fed wheat-soy-based starter (d 0-14) and grower diet (d 14-35). There were eight dietary treatments replicated six times in 48 floor pens: negative control (NC) treatment with no supplemental Cu, 15 and 200 mg/kg Cu from CuSO₄or 15, 50, 100, 150 and 200 mg/kg Cu from CH. On d 14, the pooled caecal contents from three sacrificed birds per replicate were collected for microbial group analysis by real-time quantitative PCR, a 1-cm section of jejunum from each bird was collected for gene expression analysis. Mid jejunum sections were collected for morphology measurement on d 35.

Birds fed diets supplemented with Cu from CH had longer villi compared to those fed CuSO₄supplemented at either level (15 or 200 mg/kg) (P < 0.01), reflecting better absorption of nutrients in the intestine. Increasing dietary Cu linearly decreased the population of both beneficial bacteria - Lactobacillus (P = 0.032), and pathogenic groups - Bacteroides (P = 0.033) and Enterobacteriaceae (P = 0.028). Copper supplementation at 200 mg/kg from CH inhibited the growth of Bacteroides and Enterobacteriaceae compared with the NC diet and 200 mg/kg CuSO₄ supplemented diet. CH may have a higher concentration of free Cu-Cu ions at lower parts of the intestine which is soluble and can penetrate into the bacterial cells then change the enzyme activity of the bacteria, leading to bacterial death. Neither copper level nor source had an impact on the mRNA expression of jejunal genes involved in gut integrity (claudin-1, claudin-5, junctional adhesion molecule B, occludin, tight junction protein-1) (P > 0.05). This indicates that that the NC diet was not severely deficient in Cu, and a high level of Cu supplementation, up to 200 mg/kg, does not negatively affect gut permeability in broilers.

In conclusion, supplementation of broiler diets with copper at growth-promoting levels (up to 200 mg/kg) in the CH form alters gut microbiota composition but does not negatively affect gut integrity. Supplementation with copper from CH could be beneficial over CuSO₄at improving intestinal morphology.

ACKNOWLEDGEMENTS: This study was funded by Trouw Nutrition, a Nutreco company.

Presented at the 34th Annual Australian Poultry Science Symposium 2023. For information on the next edition, click here.