General
All animal experimentation procedures were approved by the Institutional Animal Care and Use Committee at China Agricultural University (Beijing, China). Two experiments were conducted in the Metabolism Laboratory of the Ministry of Agriculture Feed Industry Centre (China Agricultural University, Beijing, China). The DLRSM samples were obtained from the main double-low rapeseed producing areas in China. All samples were solvent-extracted DLRSM. Thirteen meals were selected from the collected 20 DLRSM to achieve the greatest variability (Table 1). However, only 10 of the collected 20 DLRSM were selected to determine their ileal AA digestibility. The chemical composition and AA content of these DLRSM are shown in Tables 2 and 3. The diets in both experiments were all fed as mash. The pigs were fed the diets equal to 4 % of their body weight (BW) and the daily feed allowance [13] was offered in two equal meals at 0800 and 1700 h. Water was freely available at all times throughout the experiment. The barrows were individually placed in stainless-steel metabolism crates (1.4 m × 0.45 m × 0.6 m) in a temperature-controlled room (22 ± 2 °C). The pigs used in both experiments were crossbred (Duroc × Landrace × Yorkshire) barrows obtained from Fengning Swine Research Unit, China Agricultural University (Beijing, China).