Effects of rapeseed meal on laying performance and egg quality in laying ducks

This study was conducted to investigate the effect of different varieties of rapeseed meal (RSM) with different concentrations of glucosinolates (Gls) and erucic acid (EA) on performance and egg quality of laying ducks. A total of 576 twenty eight-wk-old laying ducks were randomly allocated to 4 treatments. Each treatment had 8 replicates of 18 laying ducks raised in 6 adjacent cages with 3 laying ducks per cage. The control diet was corn soybean meal based without RSM. Three varieties of RSM varying in Gls concentrations were supplemented to the base diet at 10% by substituting soybean meal to formulate the three RSM diets. The experiment lasted 12 wk. Diets with 10% RSM decreased average egg weight (P < 0.01) and feed intake (P = 0.07) compared with the control diet, but there was no significant difference in laying performance among the 3 RSM diets. RSM increased color value (P < 0.05) and crude protein (CP) content (P < 0.05) of yolk compared with the control diet, but had no significant effects on the other egg quality indexes including eggshell strength, albumen height, Haugh unit, and the composition ratio of eggshell, albumen and yolk. RSM decreased total monounsaturated fatty acids (MUFA) (P < 0.01) and increased total polyunsaturated fatty acids (PUFA) (P < 0.01) of yolk, but total saturated fatty acids (SFA) proportions and UFA/SFA ratio of egg yolk were not significantly affected by RSM. RSM increased deposition of trimethylamine (TMA) and 5-vinyl-1,3oxazolidine-2-thione (5-VOT) in yolk (P < 0.01); moreover, the high Gls RSM increased deposition of TMA (P < 0.01) and 5-VOT in yolk (P < 0.01) compared with the RSM varieties low in Gls. These results suggested that dietary inclusion of 10% RSM decreased egg weight of laying ducks, and affected yolk quality especially yolk color, fatty acid profile, CP, TMA, and 5-VOT content of yolk. Moreover, RSM with higher Gls concentration resulted in higher deposition of TMA and 5-VOT in egg yolk.