Feed supplementation with Ligilactobacillus salivarius PS21603 optimises intestinal morphology and gut microbiota composition in weaned piglets

Abstract Post-weaning diarrhoea in piglets remains an important cause of economic losses for swine producers. Feed supplementation with probiotics is one of the alternatives to antibiotics used to reduce the impact of such gastrointestinal disease. The aim of the present study was to evaluate the effect of Ligilactobacillus salivarius PS21603 supplementation on the intestinal structure and the gut microbiota composition of weaned piglets. Safety and tolerance of L. salivarius PS21603 were previously evaluated in a 28-days study using 384 weaned piglets (28 ± 2 days old and 7.5 ± 1.5 kg) divided in three treatment groups: T1: Basal diet + L. salivarius PS21603 10 9 cfu/day, T2: Basal diet + L. salivarius PS21603 10 7 cfu/day, and T3: Basal diet (control group). For the present study, 16 piglets per treatment group were randomly selected and faecal samples were collected on day 0 (weaning) and 28 of study. At the end of study, three males and three females per treatment were euthanised. Intestinal morphometric values were measured after necropsy. Faecal counts of Escherichia coli were evaluated by culture techniques, and faecal microbiota composition was assessed by high-throughput sequencing. All data were analysed and compared between treatment groups. Supplementation with L. salivarius PS21603 caused an increase in the intestine length of piglets from T1 and in the villous height:crypt ratio of piglets from T2 ( P < 0.05) compared to T3 on day 28. According to the Shannon Diversity Index, microbiota diversity increased on day 28 compared to day 0, with no significant differences observed between treatments. The main changes in the relative abundance of bacteria at the phylum, family, and genus levels were observed between different sampling time points. However, piglets from T1 and T2 had lower faecal E. coli counts than T3 on day 28 ( P < 0.05). Moreover, supplementation with L. salivarius PS21603 modulated gut microbiota through a more optimal composition, reducing Escherichia and increasing Bifidobacterium relative abundance in piglets from T1 ( P < 0.05) from the beginning to the end of the study. Therefore, the strain L. salivarius PS21603 has shown probiotic properties to be used as feed additive in the pig industry, along with good hygiene and farm management practices, for the prevention and/or treatment of post-weaning diarrhoea in piglets.