| A large number of studies have shown that adding moderate doses of trivalent chromium in feed can significantly improve the growth performance and quality of meat. But many farmers often added excessive trivalent chromium in the process of large-scale farming in order to in pursuit of greater economic benefits; however, a lot of toxic events caused by chromium have been widely reported. So people pay more attention to the toxic effects of trivalent chromium on the breeding process. There is little study about the toxicity of chromium on poultry in vivo, so it is necessary to explore the toxic effects of chromium on animals. Our study aimed to investigate the effects of growth performance, renal oxidative damage and the changes in the contents of trace elements induced by trivalent chromium in Hyline brown chickens, providing a scientific basis for the toxic effects of chicken.The acute experiment through lavage was done to calculate the median lethal dose(LD50) of chromium trichloride by Horn method, and the LD50 was 5013 mg/kg body weight. A total of 72 chickens were divided into four groups to do the chronic poisoning experiment for 42 days: 3 experimental groups, the high-dose group(1/2 LD50 Cr Cl3), middle-dose group(1/4 LD50 Cr Cl3) and low-dose group(1/8 LD50 Cr Cl3), which were administrated Cr Cl3 solution orally; the control group with the same dose of distilled water. All the chickens were access to the same standard feed. The mass of body, chest, leg muscle and kidneys were used to measure the impact on the growth and development. The oxidative damage of kidneys was measured through pathological histology, the activity of antioxidant enzyme and the content of non-enzyme substances. The contents of trace elements in the organs were detected by flame atomic absorption spectrophotometry. Results showed that as the increasing time and dose of poisoning, the growth rate decreased significantly(P < 0.05). The body weight in the three Cr-treated groups was obviously lower than the control groups on 14 d, 28 d and 42 d, respectively. The mass of chest muscle, leg muscle and kidney in the three Cr-treated groups was also significantly(P < 0.05) lower than the control groups with a relationship between dose and time. The experimental groups presented similar damages, including slight swelling, nuclear condensation, and dissolution in the tubular epithelial cells. A part of the renal tubules showed severely swelling or enlarged lumen, and some membrane of epithelial cells dissolved or disappeared. In the high- and middle-dose groups, the medulla units were hemorrhage, and renal tubule showed severe atrophy. Moreover, the structure of glomerulus was degenerative; and the renal capsule lumen significantly largened. Yellow substances were found in the renal distal tubules. These substances were speculated as renal granular casts, which were produced by the tubule damage caused by heavy metal poisoning. In the low dose and control group the pathological changes was not obvious. The total antioxidant capacity(T-AOC) in the three Cr-treated groups was decreased significantly(P < 0.05) as the increasing time and dose of poisoning; and the activities of the antioxidant enzymes(SOD, GSH-PX, CAT) were also decreased significantly(P < 0.05). The content of hydrogen peroxide(H2O2) reduced but was higher than the control groups. The contents of glutathione(GSH) and malondialdehyde(MDA) increased significantly(P < 0.05) with a time- and dose- dependent relationship. Elements(Cr, Ca, Mg, Mn, Fe, Cu and Zn) determination showed that the contents of Cr in the organs increased significantly(P < 0.05), however, the content of Cr reached saturation on 42 d that didn’t increase at all. In the serum, the contents of Ca, Fe and Cu increased significantly(P < 0.05) with the increasing time and dose, the rest decreased. In the heart and liver tissues, in addition to Fe, the contents of other elements decreased significantly(P < 0.05) with the increasing time and dose. In the kidney and brain tissues, the content of Ca increased with the increasing time and dose but other elements decreased significantly(P < 0.05). Summarizing, it could preliminarily concluded that oral administration of chromium trichloride in the drinking water can lead to growth retardation of chicken, oxidative damage and dysfunction of kidney, and interfer the elements metabolic pathway to change the element content with a time- and dose- dependent relationship in the body. |
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