Safety Evaluation of an Intranasally Applied Cocktail of Lactococcus lactis Strains in Pigs

SIMPLE SUMMARY: In this study, the safety of an intranasally applied cocktail of Lactococcus lactis was evaluated in new-born pigs. Prior to farrowing, twelve sows were assigned to either a placebo or cocktail group. Immediately after farrowing, either the placebo or cocktail was applied to both nostrils of all piglets in the corresponding group. Piglet health and growth were monitored at regular intervals, and on three occasions piglets were necropsied and samples were collected from the respiratory tract to identify any changes caused by the treatment. The results show that the cocktail did not negatively impact piglet growth or health, nor did it cause histological changes in the nasal conchae, tonsils or lung tissues; but it did alter the gene expression of pBD2, TLR9 and IL-1β in the nasal conchae. These findings indicate the cocktail is safe for administration to pigs. ABSTRACT: Three Lactococcus lactis strains from the nasal microbiota of healthy pigs were identified as candidates for reducing MRSA in pigs. The safety of nasal administration of a cocktail of these strains was examined in new-born piglets. Six days pre-farrowing, twelve sows were assigned to the placebo or cocktail group (n = 6/group). After farrowing, piglets were administered with either 0.5 mL of the placebo or the cocktail to each nostril. Health status and body weight were monitored at regular time points. Two piglets from three sows/treatment group were euthanised at 24 h, 96 h and 14 d after birth, and conchae, lung and tonsil samples were collected for histopathological and gene expression analysis. Health scores were improved in the cocktail group between d1–5. Body weight and daily gains did not differ between groups. Both groups displayed histological indications of euthanasia and inflammation in the lungs, signifying the findings were not treatment related. The expression of pBD2, TLR9 and IL-1β in the nasal conchae differed between groups, indicating the cocktail has the potential to modulate immune responses. In summary, the L. lactis cocktail was well tolerated by piglets and there was no negative impact on health scores, growth or lung histopathology indicating that it is safe for administration to new-born piglets.