Determination of relative bioavailability of copper in tribasic copper chloride to copper in copper sulfate for broiler chickens based on liver and feather copper concentrations

• Copper bioavailability was determined based on liver and feather copper contents.
• Copper bioavailability varies with target tissues of broilers, but insignificantly.
• Relative bioavailability of copper can be measured with feather copper contents.

This experiment was conducted to determine the relative bioavailability (RBV) of copper (Cu) in tribasic copper chloride (TBCC) to Cu in copper sulfate (monohydrate form; CuSO4·H2O) as a reference Cu source for broiler diets based on liver and feather Cu concentrations. A total of 588 1-day-old broiler chicks were randomly allotted to 1 of 7 dietary treatments with 7 replicate cages of 12 birds each (6 males and 6 females). Birds were fed the corn–soybean meal-based basal diet (8.76 mg/kg Cu), or basal diets supplemented with 0, 100, 200, or 300 mg/kg Cu from either CuSO4 or TBCC for 21 d. Results indicated that birds fed diets containing 300 mg/kg of Cu from CuSO4 had the least (P < 0.05) average daily gain (ADG) and average daily feed intake (ADFI) among 7 dietary treatments. The ADG and ADFI were less (P < 0.01) for birds fed diets containing CuSO4 than for those fed diets containing TBCC. Birds fed diets containing 300 mg/kg of Cu had greater (P < 0.01) liver and feather Cu concentrations than those fed diets containing 100 or 200 mg/kg of Cu. The RBV of Cu in TBCC to Cu in CuSO4, when it was calculated based on log10 transformed liver Cu concentrations and added Cu intake, was 92.6 ± 7.9%, whereas the RBV of Cu in TBCC to Cu in CuSO4 determined using feather Cu concentrations was 84.3 ± 8.4%. However, these two values were not significantly different. In conclusion, the RBV of Cu in TBCC to Cu in CuSO4 varies with target tissues, but the values are not significantly different. Thus, the RBV of Cu in TBCC to Cu in CuSO4 can also be determined using feather Cu concentrations in broiler chickens. From a practical standpoint, the RBV is likely close to 88.5% when values determined from liver and feather Cu concentrations are averaged.