Effects of dietary rapeseed meal on laying performance, egg quality, apparent metabolic energy, and nutrient digestibility in laying hens

The objective of the present study was to investigate the effects of low glucosinolates rapeseed meal (RSM) on laying performance, egg quality, nutrient digestibility, and AME in laying hens. A total of 900 thirty-week-old laying hens were randomly assigned to 6 dietary treatments with 10 replicates per treatment and 5 cages (3 hens) per replicate. The isoenergetic and isonitrogenous diets containing 0, 58.8, 117.6, 176.4, 235.2, and 294.0 g RSM/kg were formulated on a digestible amino acid basis. The study lasted for 12 wk. Results showed that the egg production and egg mass linearly decreased with the increased content of RSM (P < 0.01), and the feed conversion ratio (FCR) increased linearly during wk 1 to 12 (P = 0.003). The increasing RSM content had a quadratic effect on average egg weight (P < 0.01) and average daily feed intake (ADFI, P < 0.01) during wk 1 to 12. The increasing RSM content had a quadratic effect on apparent metabolic energy (AME), N, and amino acid digestibility at wk 12 (P < 0.04), except Tyr and Ser. Dry matter, Tyr, and Ser digestibility linearly decreased as the RSM concentration increased at wk 12 (P < 0.01). The egg albumen height decreased linearly at wk 4 and 12 (P < 0.01 and P = 0.02, respectively), and Haugh units decreased in a linear manner at wk 4 and 12 (P = 0.03 and 0.02). The egg yolk color increased linearly with increased content of RSM at wk 4 and 12 (P < 0.01). The serum triiodothyronine (T3) and thyroxine (T4) linearly increased as the RSM content increasing (P < 0.01). Using a one-slope broken-line analysis, the breakpoint (BP) for egg weight of daily RSM intake during wk 1 to 12 occurred at 13.6 g/hen. The daily RSM intake BP of egg production at wk 1 to 12 occurred at 6.5 g/hen. Supplementation of low glucosinolate RSM in hens' diet should be lower than 117.6 g/kg in terms of egg production performance, egg quality, blood hormone content, nutrient digestibility, and AME.