Effects of adding different levels of Aspergillus niger on in vitro fermentation parameters, methane emissions, and microbial community in dairy cow rumen

Abstract: To investigate the effects of dietary supplementation with different sources of probiotics on the growth performance, serum immunity and antioxidant function, apparent nutrient digestibility, and fecal microorganisms of weaned piglets, this study employed a single-factor experimental design. One hundred and fifty-six healthy Duroc × Landrace × Large White crossbred weaned piglets were randomly divided into four groups (three replicates per group, with 13 piglets per replicate): an antibiotic group (basal diet + 0.15 g/kg chlortetracycline, AN group), a low-concentration Bacillus licheniformis preparation group (basal diet + 0.5 g/kg Bacillus licheniformis preparation, LBL group), a high-concentration Bacillus licheniformis preparation group (basal diet + 1.0 g/kg Bacillus licheniformis preparation, HBL group), and an Enterococcus faecalis preparation group (basal diet + 0.5 g/kg Enterococcus faecalis preparation, EF group). The experimental period was 28 days. The results showed that: 1) Compared with the AN group, the final weight of the HBL and EF groups was significantly increased (P<0.05), the average daily gain (ADG) of the HBL and EF groups was significantly increased (P<0.05), and the feed conversion ratio (F/G) of the LBL group was significantly decreased (P<0.05); compared with the LBL group, the average daily feed intake (ADFI) of the EF group was significantly increased (P<0.05). 2) Compared with the AN group, the serum levels of immunoglobulin A (IgA), interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the LBL and EF groups were significantly increased (P<0.05), the serum malondialdehyde (MDA) level in the EF group was significantly decreased (P<0.05), and the serum catalase (CAT) activity in the LBL group was significantly increased (P<0.05). 3) Compared with the AN group, the apparent digestibility of crude protein in the HBL group was significantly increased (P<0.05). 4) Compared with the AN group, the relative abundance of Firmicutes was decreased in the LBL and HBL groups, while it was increased in the EF group; the relative abundance of Actinobacteria was increased in all experimental groups, and the relative abundance of Bacteroidetes was increased in the LBL group. In conclusion, adding probiotics to the diet can improve the growth performance of weaned piglets, enhance immunity and antioxidant capacity, and improve fecal microbial composition. The effect of adding Enterococcus faecalis was superior to that of adding Bacillus licheniformis.