AUTHOR=Schwaiger Karin , Storch Julia , Bauer Christoph , Bauer Johann 

TITLE=Lactobacillus (Limosilactobacillus) reuteri: a probiotic candidate to reduce neonatal diarrhea in calves

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1266905

DOI=10.3389/fmicb.2023.1266905

ISSN=1664-302X

ABSTRACT=<sec id="sec1"><title>Background</title><p>Diarrhea in newborn calves is considered life-threatening and results in large economic losses in dairy farms. Lactobacilli generally play an important role in intestinal health, and <italic>Lactobacillus</italic> (<italic>Limosilactobacillus</italic>; <italic>L.</italic>) <italic>reuteri</italic> is the dominant <italic>Lactobacillus</italic> species in the feces of healthy calves during the first week of life. In calves with diarrhea on day 2 postpartum, lactobacilli are significantly reduced even up to 24 h before the onset of clinical signs. Since the probability of occurrence of diarrheal disease decreases as the <italic>L. reuteri</italic> count in the feces increases, oral administration of this species might have a protective effect against diarrhea.</p></sec><sec id="sec2"><title>Objective</title><p>These studies were designed to demonstrate whether oral administration of preselected <italic>L. reuteri</italic> isolates can reduce the incidence of diarrhea in newborn calves on dairy farms.</p></sec><sec id="sec3"><title>Microorganisms</title><p>46 <italic>L. reuteri</italic> isolates from 2-day-old healthy calves were available from a previous study.</p></sec><sec id="sec4"><title>Animals</title><p>170 newborn calves of Simmental breed of 10 dairy farms in Bavaria (Germany), were included in the study; of 166 animals the data could be evaluated.</p></sec><sec id="sec5"><title>Methods</title><p>Microbiological (antibiotic sensitivity test, acid and bile salt stability test, antimicrobial activity of the supernatants), molecular biological (PCR, RAPD-PCR) and toxicological methods (MTT test) were used to select and to characterize suitable <italic>L. reuteri</italic> isolates. The administration of a suspension of two selected <italic>L. reuteri</italic> isolates (6–8 × 10<sup>8</sup> colony forming units per day) to calves was performed from day 2 to day 5 after birth in a double-blinded placebo-controlled study. Clinical monitoring of the calves continued until the 14th day of life.</p></sec><sec id="sec6"><title>Results</title><p>Out of 46 <italic>L. reuteri</italic> isolates, only 2 met the set criteria and were used in the feeding trial. In the placebo group, 44 of 83 calves developed diarrhea within the first 2 weeks of life, whereas in the <italic>L. reuteri</italic> group this was only the case in 31 of 83 animals (<italic>p</italic> &lt; 0.05).</p></sec><sec id="sec7"><title>Conclusion</title><p><italic>L. reuteri</italic> appears to be of particular importance for the intestinal health of newborn calves. The diarrhea protective effect could be even more pronounced if an improved administration regimen is developed in terms of start, frequency, and duration.</p></sec>