Replacing soybean meal with fermented rapeseed meal improves growth performance and intramuscular fat deposition in growing-finishing pigs.

This study aimed to investigate the effects of replacing soybean meal (SBM) with fermented rapeseed meal (FRSM) on growth performance, nutrient digestion and absorption, carcass characteristics and meat quality in growing-finishing pigs. Eighty-four 80-d-old healthy pigs (initial body weight: 33.65 ± 0.62 kg) were randomly assigned to four dietary groups: SBM group (corn-SBM diet), 50%RSM group (hot pressed RSM replacing 50%SBM on an isonitrogenous basis), 50%FRSM group, and 100%FRSM group (FRSM replacing 50% or 100%SBM on an isonitrogenous basis). Each group consisted of 7 replicates of 3 piglets for a 91-d trial. Results indicated that 50%FRSM and 100%FRSM groups showed numerically increased average daily feed intake and average daily gain in pigs during 30 to 125 kg phase compared to SBM and 50%RSM groups (P > 0.05). The mRNA level of jejunal taste receptor (T1R1 and ENaC) in pigs significantly increased in 50%FRSM and 100%FRSM groups compared to 50%RSM groups (P < 0.05), while the mRNA level of POMC in hypothalamus exhibited an inverse pattern (P = 0.001). Regarding nutrient absorption, the mRNA levels of jejunal nutrient transporters (CAT1, PepT1, and SGLT1) in the 100%FRSM group were significantly higher than those in the SBM and 50%RSM groups (P < 0.05). Longissimus dorsi intramuscular fat content was significantly higher in the 50%FRSM and 100%FRSM groups than in the SBM group (P = 0.005). Further analysis showed that 100%FRSM diet upregulated mRNA expression of lipid metabolism-related genes (FATP, DGAT1, and PID1) (P < 0.05) and increased lactate dehydrogenase activity in longissimus dorsi muscle (P = 0.017). In conclusion, supplementation with FRSM numerically improves the growth performance of growing-finishing pigs by enhancing feed intake and nutrient absorption, and promotes intramuscular fat deposition through enhanced lipid and energy metabolism. The results suggest FRSM can serve as a viable alternative plant protein for swine diets.