Influence of different Carbohydrate Composition in Barley Varieties on Salmonella Typhimurium var. Copenhagen Colonization in a ’Trojan’ Challenge Model in Pigs

Based on previously performed in vitro studies, which showed that hulless barley varieties could reduce large intestinal Salmonella Typhimurium var. Copenhagen proliferation in pigs, two in vivo experiments were conducted with a total of 252 piglets to prove these observations. In experiment 1, 126 weaning piglets were randomly allocated into pens of seven animals each and fed one of 6 experimental diets. Three diets contained (75% as-fed) one of 3 hulless barley varieties with -glucan (BG) contents ranging from 5-11% and amylose from 5-40%, and two diets contained a low BG and amylose hulless barley supplemented with isolated barley BG or raw potato starch. A hulled barley diet served as a control. Two piglets per pen (’Trojan’ pigs) were orally infected with Salmonella Typhimurium var. Copenhagen (ST). The remaining 5 pigs per pen were designated ’Contact’ pigs. The ST shedding was determined over one week after infection. On day 6, the two trojans and two random contacts from each pen were euthanized and intestinal contents and mesenteric lymph nodes cultured for ST. Intestinal volatile fatty acids and microbial composition were determined. In experiment 2, 126 piglets were assigned to one of 3 diets based on hulled or hulless barleys. The timeline, infection, sampling and analyses were similar as in experiment 1 except samples were taken from 4 contacts pigs. Hulless barley varieties with high BG and amylose tended to decrease ST persistence in experiment 1. Clostridia from cluster I in the colon were reduced with high amylose hulless barley or diets supplemented with potato starch (p<0.05), whereas other microbial groups were not. Propionate increased (p<0.05) and acetate decreased (p<0.05) with hulless barley inclusion. Using more experimental units per barley, experiment 2 revealed a reduced ST shedding and reduced number of clostridia for high BG hulless barley as compared to common hulled barley and a low BG variety (p<0.05). In conclusion, high BG hulless barley do not prevent ST colonization but might help to reduce transmission in pigs, likely by supporting an intestinal environment limiting growth of this zoopathogen.