This study was conducted to investigate the effect of increasing dietary levels of inorganic
chromium (CrCl3 x 6H2O) on the performance, blood chemistry, and immune response of broilers. Eighty newly hatched Ross PM3 broiler chicks were evenly distributed to five groups of 16 chicks each. Two groups (control and only sheep red blood cell inoculated) were fed the basal diet containing 2.2 and 4.5 mg Cr/kg and the remaining groups were fed 20, 40, or 80 mg/kg Cr-supplemented diets for 44 d. Chicks in all groups, except in the control, at 3 and 5 wk of age, were injected intraperitonally with sheep red blood cell for determining the primary and secondary antibody responses, respectively. When the chicks were 4 wk of age, a delayed-type
hypersensitivity test was performed. White blood cells were differentiated. Blood samples were collected for the determination of
serum proteins,
glucose,
cholesterol,
cortisol, minerals, and
alkaline phosphatase activity and for antibody response.
Chromium had no effect on
weight gain, but 20 mg/kg supplemental Cr resulted in 18.57% reduction in feed consumption and improved feed efficiency by 16.77%.
Chromium did not affect serum
cholesterol and P levels but reduced serum
glucose and increased
serum protein, Cr, Ca, and Mg levels, and ALP activity. A slight reduction was observed with Cr supplementation in
cortisol levels. Slight but not significant increases were observed with Cr in serum Zn and Cu.
Chromium increased the ratio of bursa of Fabricius and liver to
body weight. Heterophil and monocyte counts and heterophil/lymphocyte ratio were reduced and lymphocyte counts, total
antibody, IgG, and
IgM titers were increased by supplemental Cr. All levels of Cr increased the cell-mediated response to
phytohemagglutinin. No alterations in tissues were observed by histopathological examinations.