Effects of Rapeseed Feeding on Swine Metabolome

Rapeseed meal (RSM) is a rich source of amino acids, lipids, fiber, minerals, and vitamins. Despite its favorable nutrient content, the antinutrient properties of bioactive phytochemicals within rapeseed pose as challenges in adopting rapeseed meal as a major component of swine feed. In this study, the control diet containing 14% soybean meal (SBM) and the rapeseed diet containing 20% RSM were formulated to have similar NE and standardized ileal digestible amino acid content. To understand the influences of RSM feeding on metabolic homeostasis, 40 nursery pigs, initial BW 17.8 ± 2.7 kg, were equally spilt-up into two groups, and pair-fed with control and rapeseed diets, respectively. On d21, all pigs were sacrificed for harvesting serum, digesta, and liver samples. All samples were examined by LC-MS-based metabolomic analysis for determining the metabolic effects of these two diets. Rapeseed exposure markers, including; sinapine, sinapic acid, and gluconapin, were identified in the digesta by an unsupervised principal component analysis (PCA) model and metabolite characterization, Furthermore, different distribution of free amino acids in the intestine was observed between the two meals. However, feeding RSM did not significantly affect the levels of microbial metabolites in the digesta, including short-chain fatty acids and secondary bile acids, in spite of 2% greater NDF content. As for serum and liver extracts, the separation of rapeseed diet from control was only achieved in the supervised partial least squares-discriminant analysis (PLS-DA) model, but not in the PCA model, suggesting that limited metabolic differences existed between the two feeding groups. Nevertheless, oxidized metabolites, including oxidized glutathione, cystine, and pyroglutamate, as well as triacylglycerol/phospholipid ratio were positively correlated with rapeseed diet in the model, while ascorbic acid in the liver was negatively associated with it. These observed metabolic changes suggest the occurrence of oxidative stress after short-term RSM feeding, and warrant further studies on their correlations with growth performance in long-term feeding.