1. This study was conducted to investigate the effects of methionine and betaine supplementation on growth performance, carcase composition and lipid metabolism in growing broilers. 2. A total of 450 commercial broilers, 22 d of age, were randomly allocated to three groups, each of which included three replicates (50 birds per replicate). The groups received the same methionine-deficient diet supplemented with 0 or 1 g/kg methionine, or 0·5 g/kg betaine, respectively. 3. Methionine and betaine supplementation significantly improved weight gain and feed conversion. Supplemental methionine and betaine also significantly increased breast muscle yield and decreased abdominal fat content. Meanwhile, addition of methionine and betaine significantly increased the contents of creatine and free carnitine in liver, the activity of hormone-sensitive lipase in abdominal fat and the concentration of free fatty acid in serum, whereas uric acid concentration in serum was significantly decreased. 4. The results of this study suggest that betaine can spare methionine in its function as an essential amino acid and is as effective as methionine in improving performance and carcase quality of growing broilers if the diet is moderately deficient in methionine. The decrease in abdominal fat may be due to the increased carnitine synthesis in liver and hormone-sensitive lipase activity in abdominal fat.

Weaning stress in piglets can lead to poor health outcomes and reduced production. We investigated the effects of probiotics, one potential antibiotic alternative, on the growth performance, serum biochemical parameters, intestinal morphology, mucosal immunity, hypothalamic neurotransmitters, and colonic microflora in weaned piglets. Thirty-six weaned piglets were fed a basal diet, a diet supplemented with colistin sulphate antibiotic, or a diet supplemented with probiotics including Clostridium butyricum, Bacillus subtilis, and B. licheniformis. Probiotics significantly increased the feed : gain ratio, improved the average day gain from day 1 to day 28, and decreased the diarrhoea index. Probiotics also lowered the serum concentrations of AST, ALT, and ALP on day 14 and lowered the serum concentration of ALT on day 28 compared with the control. Probiotic supplementation caused fewer ileal apoptotic cells. The serum and ileal concentrations of TNF-α and IL-1β on day 28 were significantly lowered, and the serum concentrations of IL-6 were significantly lowered on days 14 and 28. Probiotic-fed piglets exhibited higher contents of hypothalamic serotonin and dopamine as well as serum γ-aminobutyric acid along with higher colonic concentrations of butyrate and valerate on day 28. High-throughput sequencing showed 972 core operational taxonomic units among all groups, of which 48 were unique to the probiotic-treated group. The relative abundance of genus Bacillus and species Bacillus velezensis was enriched in probiotic piglets; the phylogenetic investigation of communities by the reconstruction of unobserved states indicated that amino acid metabolism, DNA repair, replication and recombination proteins, and secretion systems were enriched with probiotics. In conclusion, the Clostridium butyricum-based probiotics improved growth performance, enhanced intestinal morphology, changed hypothalamic neurotransmitters and modulated colonic microflora in weaned piglets.

The present study investigated the effect of Bacillus subtilis DSM 29784 (Ba) and enzymes (xylanase and β-glucanases; Enz), alone or in combination (BE) as antibiotic replacements, on the growth performance, digestive enzyme activity, immune response and the intestinal barrier of broiler chickens. In total, 1200 1-d-old broilers were randomly assigned to five dietary treatments, each with six replicate pens of forty birds for 63 d as follows: (a) basal diet (control), supplemented with (b) 1 × 10⁹ colony-forming units (cfu)/kg Ba, (c) 300 mg/kg Enz, (d) 1 × 10⁹ cfu/kg Ba and 300 mg/kg Enz and (e) 250 mg/kg enramycin (ER). Ba, Enz and BE, similar to ER, decreased the feed conversion rate, maintained intestinal integrity with a higher villus height:crypt depth ratio and increased the numbers of goblet cells. The BE group exhibited higher expression of claudin-1 and mucin 2 than the other four groups. BE supplementation significantly increased the α-diversity and β-diversity of the intestinal microbiota and markedly enhanced lipase activity in the duodenal mucosa. Serum endotoxin was significantly decreased in the BE group. Compared with those in the control group, increased superoxide dismutase and glutathione peroxidase activities were observed in the jejunal mucosa of the Ba and BE groups, respectively. In conclusion, the results suggested that dietary treatment with Ba, Enz or BE has beneficial effects on growth performance and anti-oxidative capacity, and BE had better effects than Ba or Enz alone on digestive enzyme activity and the intestinal microbiota. Ba or Enz could be used as an alternative to antibiotics for broiler chickens.