Effects of dietary net energy and fibre-degrading enzymes on growth performance and gut microbiota in growing-finishing pigs

ABSTRACT This study aimed to evaluate the effects of dietary net energy (NE) and fibre-degrading enzymes on growth performance, nutrient digestibility, serum biochemical and inflammatory markers, faecal short-chain fatty acids （SCFA） and microbiota composition in growing-finishing pigs. A total of 192 crossbred pigs (69.40 ± 1.95 kg) were randomly allocated to 4 dietary treatments (2 × 2 factorial: high/low NE with/without enzyme) in a 35 d trial, with each group comprised 6 replicates (8 pigs per replicate, 4 barrows and 4 gilts). A reduced NE led to a lower average daily gain, whereas the fibre-degrading enzyme supplementation tended to increase the ADG (P = 0.09) and acid detergent fibre digestibility (P < 0.01). The blood urea nitrogen concentration was lower in pigs fed a lower NE level or supplemented with fibre-degrading enzymes. Pigs fed diets supplemented with fibre-degrading enzymes presented lower serum interleukin-1β levels; greater relative abundances of beneficial microbes, such as Akkermansia and Prevotellaceae UCG-001 (P < 0.05); and higher faecal concentrations of acetate and butyrate (P < 0.05). In conclusion, fibre-degrading enzymes partially mitigated the decline in ADG caused by a 40 kcal/kg reduction in dietary NE level by improving fibre utilization and modulating the gut microbiota composition, thus providing a theoretical basis for reducing pork production costs.