Tibia Quality, Tissue Mineralization and Liver Lipid Peroxidation of Broilers in Response to Different Sources and Levels of Copper

Copper (Cu) is a vital element involved in various physiological and biochemical processes, namely cellular metabolism and enzyme systems. Higher levels of copper than nutritional requirements (up to 250 mg/kg) are supplemented to poultry diets. However, if in excess, excreted Cu can contaminate the environment. High levels of copper sulphate (CuSO₄) may damage other dietary nutrients through increased oxidation. Meanwhile, copper hydroxychloride (IBC) is less soluble than CuSO₄ at neutral pH; therefore it is less destructive and increases stability of essential nutrients such as vitamins and fats in the feed and within the bird (Luo et al., 2005).

This study aimed to examine the efficacy of CuSO₄ compared with that of IBC on tibia breaking strength, ash and Cu content, Cu concentration of distal ileal digesta and liver malondialdehyde (MDA) concentration in broiler chickens. A total of 864 Ross 308 male day-old chicks (41.9 ± 0.19 g) were fed wheat-soybean meal based starter diets from day 1-14 and the grower diets from day 14-35. Birds had ad libitum access to feed and water throughout the study period. 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 CuSO₄ or 15, 50, 100, 150 and 200 mg/kg Cu from IBC. On d 35, the right tibia, liver and ileal digesta samples were collected from three representative birds per replicate after euthanasia. The tibias were subjected to breaking strength by an Instron instrument. Mineral concentration in liver and ileal digesta were determined by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) technique. MDA level in the liver was determined using a lipid peroxidation (MDA) assay kit (AB118970, abcam^®, UK).

Tibia strength increased with the increments of supplemental Cu. The highest tibia breaking strength value was observed in birds given the 200 mg/kg IBC diet (338 N/mm²), suggesting higher bioavailability of Cu from the hydroxy source. The lowest tended to be seen in birds fed diets without supplemental Cu (285 N/mm², P = 0.059). Dietary treatment had no significant effect on tibia ash content (average of 45.5 %, P > 0.05) or tibia Cu content (average of 1.94 µg/g, P > 0.05). Liver Cu level was greater in birds fed the 200 mg/kg CuSO₄ diet (18.9 µg/g, P < 0.01) and 200 mg/kg IBC diet (14.6 µg/g) compared to those on any other treatment. The Cu composition of ileal digesta increased with increasing of supplemental Cu in the diets (P < 0.01). The highest ileal digesta Cu level was observed in birds fed CuSO₄ at 200 mg/kg (995 µg/g), indicating that more Cu from CuSO₄ was unavailable and excreted. The concentration of liver MDA was not significantly affected by the dietary treatments (average of 0.801 nmol/mg, P > 0.05), indicating that high dietary Cu did not negatively impact hepatic oxidation.

It can be concluded that supplementation of copper from IBC is beneficial to broiler chickens in promoting bone development. The inclusion of 200 mg/kg IBC resulted in the highest bone strength and similar organ Cu accumulation to 200 mg/kg CuSO₄.

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