Effects of Dietary Niacin Levels on Laying Performance, Egg Quality and Lipid Metabolism of Shanma Ducks during Laying Peak Period

Abstract

The aim of this study was to investigate the effects of different dietary levels of niacin on laying per⁃ formance, egg quality and lipid metabolism of Shanma ducks during laying peak period. Using a single factor completely randomized design, a total of 1 050 Fujian Longyan Shanma ducks of 24⁃week⁃old with the same body weight were randomly divided into 7 groups with 6 replicates per group and 25 ducks per replicate. The corn⁃soybean meal type basal diet was used in the experiment, and the dietary niacin supplemental levels of each group were 0 (control), 15, 30, 45, 60, 75 and 90 mg/ kg, respectively. The trial lasted for 16 weeks. The results showed as follows: 1) dietary niacin levels had no significant effects on laying performance and egg quality of Shanma ducks (P>0.05). 2) With the dietary niacin supplemental level increasing, the fat con⁃ tent in yolk was gradually decreased (P<0.05), the fat proportion in the whole egg was also gradually de⁃ creased (P<0.05), and the free fatty acid content in yolk was gradually increased (P<0.05). Compared with the control group, dietary supplementation of 75 and 90 mg/ kg niacin significantly decreased the fat content in egg yolk (P<0.05), dietary supplementation of 75 mg/ kg niacin significantly decreased the fat proportion in whole egg (P<0.05), and dietary supplementation of 45, 60, 75 and 90 mg/ kg niacin significantly increased the free fatty acid content in yolk (P<0.05). 3) Dietary niacin levels had no significant effects on plasma con⁃ tents of uric acid, cholesterol, triglyceride and low⁃density lipoprotein cholesterol (P>0.05). 4) When the di⁃ etary niacin supplemental level was 15 mg/ kg, the liver cholesterol content was significantly higher than that in the other groups (P<0.05), and the relative mRNA expression levels of liver fatty acid synthase (FAS), ste⁃ rol regulatory element binding protein 1 (SREBP1) and apolipoprotein A1 (ApoA1) were the highest. In con⁃ clusion, the dietary supplementation of niacin in the corn⁃soybean meal type basal diet has no significant effects on the laying performance and egg quality of Shanma ducks, but when the dietary niacin supplemental level ex⁃ ceeds 75 mg / kg, it can promote the lipolysis in eggs and reduce the fat content in egg yolk.