Effects of Cod Liver Oil and Chromium Picolinate Supplements on the Serum Traits, Egg Yolk Fatty Acids and Cholesterol Content in Laying Hens

This study investigated the effects of cod liver oil and chromium picolinate on the serum traits and egg yolk fatty acids and cholesterol content in laying hens. One hundred 45-week old single comb white Leghorn laying hens were assigned randomly to four groups. These groups were: (1) control (soybean oil), (2) 1,000 ppb (mg/kg) chromium (organic form chromium picolinate) (Crpic), (3) 3% cod liver oil (CLO), and (4) 1,000 ppb chromium with 3% cod liver oil (CLO+Crpic). The experiment was conducted for 40 days. Results indicated that serum triacylglycerol (TG) and cholesterol contents in the CLO group and the serum glucose content in the Crpic group were significantly lower than those in the control group (p<0.05-0.01). The yolk cholesterol content in the CLO and Crpic groups were also lower than the control group (p<0.01). The lipoprotein profile displayed that in the Crpic group, high-density lipoprotein (HDL) and HDL-cholesterol (HDL-C) were significantly higher (P<0.05) than the control group. Meanwhile, low-density lipoprotein+very low-density lipoprotein (LDL+VLDL) and LDL-C+VLDL-C were significantly lower (p<0.05) than the control group. Notably, of all four groups, the CLO group displayed a more profound effect on serum traits and lipoprotein (p<0.05-0.001). Furthermore, the fatty acid composition of the egg yolks presented that C18:2 in the CLO and Crpic groups was significantly lower (p<0.05-0.001) compare to the control. However, only in the CLO group, C18:3, C20:5 and C22:6 were significantly higher (p<0.001) than the control. Only serum glucose and LDL+VLDL showed the CLOxCrpic interaction (p<0.05), most parameters did not. Therefore, supplemented chromium picolinate or cod liver oil in the diet of laying hens had beneficial effects. However, when these two factors were combined, there was no interaction with most parameters.