Table 2.

Literature summary of effect of REE supplementation in poultry

Dose	Results and conclusions	Reference
250 mg/kg (La 100 mg, Ce 150 mg) and 500 mg/kg (La 200, Ce 300 mg) of REE in the diet of laying hen	Significant increase in plasma Ca and P levels at first and second month when supplemented group treated with REE at 250 mg/kg Whereas in group supplemented with 500 mg/kg REE plasma Ca and P had significantly increased only during first month of the trial No significant changes were reported in second month of the trial Non-significant effect on total protein, albumin and globulin level	Reka et al [49]
Lanthanum oxide (La2O3; having 85.3% La) at 100 (85.3 ppm La), 200 (171 ppm La) and 300 (256 ppm La) ppm to starter and finisher diet of broiler	Improvement in the total weight gain over the control on supplementation of La at 171 ppm Relatively lower counts of bacteria were obtained in group supplemented with 85.3 ppm La	Agbede et al [50]
Lanthanum oxide at 0, 100, 200, 300, or 400 mg/kg) in the diet of laying hen	Significant increase in Haugh unit and eggshell breaking strength Significantly decreased thiobarbituric acid reactive substance (TBARS) values in egg yolk Non-significant effect on SOD and GPx values Significant decrease in serum MDA concentration Non-significant difference in serum Ca and P level	Durmus and Bolukbası [51]
Cerium oxide at 0, 100, 200, 300, or 400 mg/kg in the diet of laying hen	Non-significant effect on feed intake and egg weight Egg production and feed conversion rate were improved by maximum level of cerium oxide (at 400 ppm) Significant decrease in SOD and MDA concentration Significant increase in serum Ca and P concentration	Bolukbası et al [52]

REE, rare earth elements; SOD, superoxide dismutase; GPx, glutathione peroxidase; MDA, malondialdehyde.