Effects of dietary supplementation with fermented flaxseed meal on the growth performance, immune function, and intestinal microbiota of growing pigs

Flaxseed meal is a highly nutritious feed resource rich in protein and unsaturated fatty acids. However, the presence of antinutritional factors such as cyanogenic glycoside limits its practical use. Fermentation has been demonstrated to degrade these antinutritional factors. However, little research has been conducted to investigate the effects of fermented flaxseed meal (FFSM) on the growth performance of growing pigs. This study thus aims to examine the effects of supplementing with 10 %, 15 %, and 20 % FFSM on the growth performance, immune function, and intestinal microbiota in growing pigs. Utilizing a completely randomized design, ninety-six growing pigs, each averaging 39.57 +/- 0.63 kg, were allocated into four dietary groups with eight replicates per group and three pigs per replicate. The dietary treatments included: a control group (corn-soybean meal-based diet without FFSM) and basal diets supplemented with 10 %, 15 %, and 20 % FFSM. The trial lasted for 30 days. Results showed that including FFSM at 10 %, 15 %, and 20 % did not affect the average daily gain and average daily feed intake of pigs. However, the gain-to-feed ratio exhibited a linear decrease as the level of FFSM increased. Furthermore, FFSM supplementation linear increases neutral detergent fiber (inclusive of residual ash) and acid detergent fiber digestibility (P < 0.05). Investigating immune parameters and metabolites revealed a linear increase in immunoglobulins (IgA and IgM) and total bile acid in serum with increasing levels of FFSM supplementation (P < 0.05). Delving deeper into the gut microbiota's complex ecosystem reveals that the quadratic response in Lactobacillus abundance and linear increase in Bacillus abundance (P < 0.05), while a linear and quadratic decrease in Clostridium_sensu_stricto_1 abundance with increasing FFSM addition (P < 0.05). Additionally, the concentrations of butyric acid and total short-chain fatty acids in feces changed quadratically with increasing proportions of FFSM (P < 0.05). The collective findings underscore the valuable role of microbial fermentation in enhancing the nutritional profile and utilization of flaxseed meal in the diets of growing pigs. Incorporation of FFSM not only augments the immune functionality of pigs but also ameliorates the balance of the intestinal microecology.