Effects Of Dietary Supplemental Chromium On Heat Stressed Laying Hens

This experiment was carried out to evalulate the effects of dietary supplemental chromium on laying performance,egg quality,blood physiological and biochemical index and nutrient utilizability in heat stressed layers in two forms of chromium yease(CrY) and chromium picolinate (CrP) .The results were as follows:1 Feeding trial 630 healthy HaiLan layers, 40 weeks of age, with similar body weight, were randomly allotted into seven groups with 3 replicates in each group and 30 hens in each replicate. The layers were fed maize-soyabean basical diets and diets supplemented with 200ug/kg, 400ug/kg, 600ug/kg of chromium as chromium yeast or chromium picolinate. Experimental period lasted for six weeks. The temperature of layers house was 28℃-35℃. The results showed that:(1) Compared with the control, laying rale were increased 3.21% {P>().05), 4.14%(P<0.05) and 4.83%(P<0.05) by supplemented 200ug/kg: 400ug/kg and 600ug/kg of chromium as chromium yeast respectively ;egg production were increased 3.37%(P>0.05)4.31%(P<0.05) and 5.07%(P<0.05) respectively. Laving rale were increased 4.25%(P<0.05),5.20%(P<0.05) and 5.76%(P<0.01) by supplemented the three similar level of chromium as chromium picolinate respectively ; egg production were increased 4.45%(P<0.05)5.41%(P<0.05) and 6.00%(P<0.01) respectively. Mortality was significantly or extremely significant decreased (P<0.05 or P<0.01) in all experimental chromium groups. Rates of broken egg were decreasded significantly. Laying rate.egg production,rate of broken egg had no difference (P>0.05) among thesupplemental chromium groups. Laying rate were increased 3.21%,4.14% and 4.83% by supplemented 200ug/kg. 400ug/kg and 600ug/kg of chromium as chromium yeast respectively;egg production were increased 3.37%,4.31% and 5.07% respectively. There was no difference among chromium levels(P > 0.05) . lntake,feed/egg and average egg weight were not affected by cliromium supplementation.(2) Egg shell thickness and calcium concentration of egg shell of 400ppb and 600ppb chromium yeast groups were significantly higher than those of control(P<0.05);cholesterol concentrations in egg yolk of 600ppb chromium chloride or cliromium picolinate were significantly lower than those of control(P<0.05); level of DM,CP and EE in egg had a lower tendency. Excessive supplementation of chromium had no influence on egg shape index and haulf unit.(3)Compared with control, content of serum total cholesterol and triglyceride and activity of ALT were remarkably lower(P<0.05), concentration of serum phosphate was significantly higher(P<0.05) in 200ppb chromium yeast; content of serum total protein , phosphate , E2 and T3 were significantly higher(P<0.05), concentration of serum triglyceride and ALT were significantly decreased(P<0.05), content of serum total cholesterol was extrenly reduced(P<0.01) in 400ppb chromium yeast; content of serum globulin, total protein, calcium, E2 and T3 were significantly higher(P<0.05), concentration of serum glucose,triglyceride LDH and ALT were significantly decrcased(P<0.05), content of serum phosphate were increased extremly(P<0.01). content of serum total cholesterol and triglyceride were reduced extremly(P<0.01) in 600ppb chromium yeast: content of serum total cholesterol and activity of ALT were remarkably lower(P<0.05), concentration of serum total protein , phosphate, E2 and T3 was significantly higher(P<0.05) in 200ppb cliromium picolinate: concentration of serum globulin and calcium were increased significantly(P<0.05 ); content of serum total protein, phosphate , E2 and T3 were extremly higher(P<0.01), concentration of serum triglyceride and ALT were significantly decreased(P<0.05) in 400ppb cliromium picolinate; content of serum globulin, albin, calcium, K+ were significantly lugher(P<0.05), concentration of serum glucose,triglyceride, cholesterol, Cl+, LDH were significantly decreased(P<0.05),content of serum total protein, phosphate, E2,T3 were increased extremly(P<0.01) activity of ALT was reduced extremly(P<0.01) in 600...