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Table 3 Optimum supplemental copper (Cu) level for broiler chicks considering sources individually or combined

From: Broiler responses to copper levels and sources: growth, tissue mineral content, antioxidant status and mRNA expression of genes involved in lipid and protein metabolism

Item Regression Eqs. 1 Optimal supplemental Cu level. mg/kg2 P-value Coefficient of determination (R2)
Body weight
  Copper levels y =  − 0.1003x2 + 1.3533x + 505.73 6.75 0.042 5.36
  CuPro y =  − 0.1296x2 + 1.9294x + 505.78 7.44 0.066 6.73
Average daily gain
  Copper levels y =  − 0.0101x2 + 0.1352x + 33.81 6.76 0.045 5.33
  CuPro y =  − 0.0129x2 + 0.1926x + 33.82 7.47 0.067 6.63
Feed conversion ratio
  Copper levels y = 0.00049x2 − 0.0091x + 1.3182 9.31 0.002 11.4
  CuPro y = 0.00044x2 − 0.0088x + 1.3038 9.87 0.041 13.7
  CuSO4.5H2O y = 0.00054x2 − 0.0095x + 1.3325 8.84 0.014 13.3
  1. CuPro (organic), copper proteinate and organic trace minerals; CuSO4.5H2O (inorganic), copper sulphate and inorganic trace minerals
  2. 1Regression equations obtained from fitting performance data to polynomial quadratic regression model Y is dependent variable and X is the supplementation Cu concentration in the corresponding diet (mg/kg)
  3. 2Cu/kg diet to a semi-purified diet containing 1.32 mg Cu/kg