Effects of dietary Lactobacillus plantarum by different supplementation methods on product quality and the palatability, biochemical parameters, and fecal microbiota composition of beagles

Abstract

Background: Probiotics exert multiple health-promoting effects on companion animals by regulating gut microbiota and immunity. However, their application is restricted by poor environmental tolerance, although various preservation techniques have been developed. Aim: This study compared the effects of external spraying (ES) and internal encapsulation (IE), two L. plantarum incorporation methods, on (1) probiotic viability during storage and tolerance to simulated gastrointestinal juices, (2) feed palatability in dogs, (3) body weight, fecal score, and serum hematological and biochemical parameters, and (4) fecal microbiota composition and apparent total tract nutrient digestibility in beagles. Methods: Lac16 strain was incorporated into a basal dog feed at 2.0 × 10¹¹ CFU/kg by either ES or IE. After 1 mo of storage at 30 °C, the viable bacteria were enumerated, and the simulated gastrointestinal tolerance of the probiotic was detected. Palatability was assessed using a 7-day two-bowl free-choice test, and health-related indicators were analyzed using a 12-beagle crossover feeding trial (2 4-week periods separated by a 4-week washout). Results: Both methods caused >99% loss of viable L. plantarum by day 60, but IE retained higher viability from day 15 onward (P < 0.05; trend at day 30, P = 0.060) and higher in vitro gastrointestinal survival (P < 0.05). The IE-processed diet possessed superior palatability relative to the ES-processed diet (P < 0.05). The fecal score was higher in the IE group on days 7 and 14 but lower on day 28 than in the ES group (P < 0.05). Most hematological and biochemical parameters did not differ, except for the high fluorescence reticulocyte percentage, which was significantly higher in the ES group than in the IE group (P < 0.05). The total apparent tract digestibility of crude protein, crude fat, calcium, and phosphorus did not differ between the groups (P > 0.05). ES showed higher fecal species richness (enriched Lactiplantibacillus and Lachnospiraceae NK4A136, P < 0.05) but not -diversity separation (P = 0.992). Conclusion: Both the IE and ES methods resulted in severe loss of viable probiotics after long-term storage. However, compared with ES, the IE method improved probiotic viability, gastrointestinal tolerance, and palatability and modified the fecal microbiota composition, while both methods had minimal effects on blood biochemical parameters and nutrient digestibility.