Effect Of Chromium Yeast On Growth And Immunity In Rex-rabbits And Study Of Application Safety

Chromium as the trace element necessary for animals, its biological activity had been paid more and more attentions by researchers. With the research progress of chromium in vivo biological effects of animals, it has been found that chromium involved in sugar, fat and protein metabolism of animals. Chromium played a role in the reduction of animal stress, and it could improve immunity, reproductive performance, carcass quality and growth, etc, particularly in regard to cattle and pigs.The experiment mainly studied the growth, immunity and feeding safety by adding chromium yeast in diet of Rex-rabbits. The effect of chromium yeast was evaluated by applying in diet with different doses in different physiological periods of Rex-rabbits. The appropriate amount of chromium yeast was determined to provided the theoretical basis for secure applications to Rex-rabbits production.Ninety-six weanling Rex-rabbits (30±2 days of age) were randomly divided into four groups, twenty-four rabbits of each. Each group was fed diet with 0, 200, 400 and 800μg/kg chromium yeast, respectively. The trial was conducted for 60d. Body absolute weights were determined on day 0, 15, 30, 45 and 60 postweaned. Then blood samples were taken from the heart for measuring serum biochemical indices, immunoglobulin (IgG, IgM, IgA) levels, lymphocyte transformation rates, leukocyte phagocytosis rates, and contents of chromium, zinc and manqanese in sera.Besides, forty youthful Rex-rabbits (3 months of age) were raddomly divided into four groups, ten rabbits of each. Each group was fed diet with 0, 2, 20 and 200μg/kg chromium yeast, respectively. The trial was conducted for 20d. Body absolute weights were determined on day 0, 10 and 20. Then blood samples were taken from the heart for measuring serum biochemical indices, immunoglobulin (IgG, IgM, IgA) levels, transaminase(ALT, AST) contents, lymphocyte transformation rates, leukocyte phagocytosis rates , and contents of chromium, zinc and manqanese in sera. At the end of the trial, the rabbits were put to death with bleed. The liver, kidney, gluteus and shankborn were taken to measure the contents of chromium, zinc and manqanese. The heart, liver, kidney spleen and lungs were taken to slice.The results were as follows:1.The diet supplemented with 400μg/kg chromim yeast markedly increased daily gain on 15d after weaning (P<0.01). It could promote growth, anti-weanling stress and immunity of Rex-rabbits.2. The diet supplemented with 200mg/kg chromium yeast would not lead to acute poisoning, but would lead to cumulational toxicity at 20mg/kg. The renal toxicity was the most obvious, followed by the liver. The growth and immune suppression had been restrained. Youthful Rex-rabbits could be tolerated 2mg/kg chromium yeast. The diet supplemented with 2mg/kg chromium yeast could keep growth and immune function normal.3. Chromium contents in sera was transient and unstable, could not represent the level of chromium in body. Serum chromium contents would not significantly change when the diet supplemented with 2mg/kg chromium. Serum chromium contents would rise sharply when the diet supplemented with 20mg/kg. Chromium was antagonist with zinc and manganese in body. With the addition of chromium in diet, animals'absorption of zinc and manganese reduced, the contents of zinc and manganese in tissues also reduced. Chromium in body was mainly in the shankborn, less in liver and kidney, and the least in muscle.