Evaluation of encapsulated probiotics administered early in newborn calves

• A higher abundance of Lactobacillus and Collinsella was observed in the treated group. • 16S rRNA sequencing revealed no structural microbiota differences between groups. • The dominant genera included Bacteroides , Prevotella , Collinsella , Alloprevotella , and Lactobacillus in both groups. • Lack of clinical impact may relate to dosage, duration, or delivery method used. This study evaluated the effects of probiotic administration on growth performance, health status, and fecal microbiota in Holstein calves. Thirty animals were assigned to two groups: the treated group of animals, from 2 to 30 days of age, received a daily oral capsule containing Lactobacillus johnsonii , Ligilactobacillus murinus , Limosilactobacillus mucosae and Ligilactobacillus salivarius (1 × 10 9 CFU per capsule), whereas the control group received placebo. Health status was monitored using the Wisconsin scoring system, and body weight was recorded at 2 and 60 days of age. Fecal microbiota was characterized at 30 ± 3 days through 16S rRNA gene sequencing. No significant differences were observed between groups regarding diarrhea incidence, weight gain, or microbiota structure. A higher relative abundance of Lactobacillus and Collinsella was observed in the treated group. En este estudio se evaluó el efecto de la administración de probióticos sobre el crecimiento, la salud y el microbioma fecal de terneros Holando Argentino. Treinta animales fueron asignados a dos grupos: el tratado recibió una cápsula oral diaria con Lactobacillus johnsonii , Ligilactobacillus murinus , Limosilactobacillus mucosae y Ligilactobacillus salivarius (1 × 10 9 UFC por cápsula) desde los 2 hasta los 30 días de vida, mientras que el grupo control recibió un placebo. El estado sanitario fue monitoreado mediante el test de Wisconsin y el peso corporal se registró a los 2 y 60 días. El microbioma fecal se analizó a los 30 ± 3 días mediante secuenciación del gen 16S rRNA. No se observaron diferencias significativas entre los grupos en la incidencia de diarreas, la ganancia de peso ni la estructura del microbioma. El grupo tratado presentó una mayor abundancia relativa de Lactobacillus y Collinsella .