Effects of different rapeseed varieties on egg production performance, egg quality, hormone levels, follicle development, and thyroid function in hens

This study was to evaluate the effects of rapeseed (<i>Brassica napus</i> L.) from China with different content of glucosinolate (Gls) and erucic acid (EA) on laying hens. A total of 600 laying hens at 33 wk of age were randomly divided into 5 treatments containing a control diet and 4 diets with 11.5% rapeseed. The 11.5% rapeseed diets varied in Gls and EA levels: 1) Deyou no. 6 (DY6) with Gls at 22.67 μmol/g and EA at 0.7%, 2) Mianbangyou no. 1 (MB1) with Gls at 43.23 μmol/g and EA at 3.5%, 3) Deyou no. 5 (DY5) with Gls at 74.66 μmol/g and EA at 16.20%, 4) Xiheyou no. 3 (XH3) with Gls at 132.83 μmol/g and EA at 44.60%. Each group had eight replicates and each replicate had 15 hens. The trial lasted for 12 wk with 4 wk withdrawal. From 1 to 8 wk of the trial, 11.5% rapeseed reduced average daily feed intake (ADFI) compared to the control group (<i>P</i> = 0.002), and egg-laying rate of XH3 rapeseed was lower than that of DY6 rapeseed (<i>P</i> = 0.006), and egg weight of MB1, DY5, and XH3 rapeseed were lower than that of the control group (<i>P</i> = 0.007). Egg mass was reduced by 11.5% rapeseed and egg mass of XH3 and DY5 rapeseed were lower than that of DY6 rapeseed (<i>P</i> = 0.004). Feed conversion ratio (FCR) of 11.5% rapeseed was higher than that the control group and FCR was higher in XH3 rapeseed than in DY6 rapeseed from 1 to 8 wk (<i>P</i> = 0.008). At wk 8, the lightness value of eggshell color of XH3 rapeseed was significantly lower than that of the control and DY5 rapeseed (<i>P</i> = 0.012). Xiheyou no. 3 rapeseed had a higher redness value of eggshell color than the control and MB1 and DY5 rapeseed (<i>P</i> = 0.008). Albumen height of DY5 rapeseed was lower than that of the control group at wk 8 (<i>P</i> = 0.012). Mianbangyou no. 1 and DY5 rapeseed decreased Haugh unit at wk 4 and 8, respectively (<i>P</i> = 0.011, <i>P</i> = 0.024). Serum estradiol (E2) content was decreased by 11.5% rapeseed (<i>P</i> = 0.003). Thyroid index increased as the Gls and EA content increased (<i>P</i> = 0.008). The smallest hierarchical follicle numbers of XH3 and MB1 rapeseed were lower than that of the control group (<i>P</i> = 0.009). After 4 wk withdrawal, the egg weight, egg mass, and FCR did not recover (<i>P</i> = 0.011, <i>P</i> = 0.033, <i>P</i> = 0.024, respectively). In conclusion, 11.5% rapeseed decreased egg production performance which might be caused by decreasing hormone levels, and high Gls and EA rapeseed had a lower performance than low Gls and EA rapeseed.