The effects of different levels of Chlorella microalgae on blood biochemical parameters and trace mineral concentrations of laying hens reared under heat stress condition. 
This study was conducted to investigate the effect of different supplementation levels of Chlorella microalgae on serum metabolites and the plasma content of minerals in laying hens reared under heat stress condition (27.5-36.7 °C, variable).  A total number of 378 (40 weeks of age, with mean body weight of 1390 ± 120 g) were randomly allocated to six treatments with seven replicates.  The birds were randomly assigned to 6 treatments (C, T1, T2, T3, T4, and T5) with 7 replicate cages of 9 birds.  C. microalgae at the rates of 100, 200, 300, 400, and 500 ppm with water were offered to groups T1, T2, T3, T4, and T5, respectively, while group C served as a control.  At 71 days of trial, blood samples (14 samples per treatment) were taken for measuring serum metabolites and at 72 days for plasma mineral analysis.  The results of this experiment showed that the supplementation of 200-500 ppm C. microalgae decreased the serum content of cholesterol, triglycerides, and LDL (P < 0.05) whereas HDL content increased (P < 0.05) in the hens supplemented with C. microalgae (300 or 400 and 500 ppm).  C. microalgae at rates of 300-500 ppm caused a marked (P < 0.05) increase in the plasma content of manganese or iodine and selenium but other minerals were not statistically different among treatments.  Overall, from the results of the present experiment, it can be concluded that supplementation of C. microalgae at high rates was beneficial on blood parameters of laying hens reared under heat stress.