On-top arginine supplementation during lactation affects milk composition, performance, and intestinal bacterial and viral microbial community of sows and their piglets.

Early gut microbiome colonization is crucial for gut physiology, immunity, and growth. It is influenced by factors like the maternal microbiome, which can be modified through diet, including amino acids (AAs) supplementation. Among AAs, arginine (Arg) is known to play a key role in lactating sows, which has attracted increased interest recently. The aim of this study was to investigate whether dietary supplementation of lactating sows with on-top Arg (22 g/d/sow) could influence the productive performance and milk of sows and their litters and their gut microbial community, including both viruses and bacteria. Thirty-two sows were divided into two groups balanced for parity and body weight: 1) control (CO) (fed a corn-based diet) and 2) CO + 22.5 g/d/sow of on-top Arg (ARG). Diets were fed from 4 d before farrowing (d4) to weaning (d27). Piglets were weighed at d0, d7, d14, d27, d34, and d41. Colostrum and milk were sampled at farrowing, d10, and d20 from proximal and immunoglobulin composition. Fecal and cecal samples were collected at d27 from sows and piglets (8 piglets/group), respectively. Arg increased the lactose content of milk collected at d20 (P = 0.05), favored the average daily gain of piglets from d0 to d41 (P = 0.04), and tended to reduce their mortality (P = 0.08). The gut microbiome of sows and piglets differed significantly in terms of bacterial and viral communities (beta diversity, P < 0.05). Bacteriophage composition differed markedly between sows and piglets, with higher Petitvirales in sows and Caudovirales in piglets (P < 0.01). Caudovirales positively correlated with Subdoligranulum, Ruminococcus, Romboutsia, and Marvinbryantia (r > 0.5; P < 0.05), which were also more abundant in piglets (P < 0.05). Arg did not affect the fecal microbial community of sows, whereas it increased the alpha diversity of the cecal bacterial (Shannon, P = 0.08) and viral (Shannon, P < 0.01) community of piglets. Piglets from ARG dams had a higher abundance of Collinsella (linear discriminant analysis [LDA] score = 4.16, P.adj = 0.05) and Cremvirales (P = 0.09) and an absence of Piccovirales (P = 0.07). In conclusion, the present study confirms the interest of Arg for lactating sows to promote piglet growth and intestinal eubiosis. The study shows that Arg administration can indirectly modify the microbiota profile of piglets at weaning. Finally, the results obtained between the viral and bacterial communities highlight the strong interplay between them, likely mediated by bacteriophages, warranting further investigation.