Understanding Age-Related Longitudinal Dynamics in Abundance and Diversity of Dominant Culturable Gut Lactic Acid Bacteria in Pastured Goats

SIMPLE SUMMARY: Evaluating age-based differences in the resident lactic acid bacteria in the gut of healthy animals is important for potential probiotic species identification and development. This gives an understanding of unique bacterial populations that are well-adapted for survival in each age group. In goats, the resident gut lactic acid bacteria diversity in different age groups has not been fully described. The objective of the study was to evaluate the abundance and identity of the lactic acid bacteria populations in different age groups of goats from birth until ten months age. We detected higher counts of lactic acid bacteria in young goat kids before weaning than goats after weaning. Additionally, we detected different lactic acid bacteria populations in the different age groups evaluated. The findings give insight on potential lactic acid bacteria species that could be targeted for the development of probiotics for different ages of goats. These results may also broadly imply that when selecting potential bacteria for probiotic evaluation in other host animals, it is important to consider the target age to ensure success of establishment in the gut. ABSTRACT: Understanding gut lactic acid bacteria (LAB) in healthy hosts is an important first step in selecting potential probiotic species. To understand the dynamics of LAB in healthy goats, a cohort of thirty-seven healthy new-born goat kids was studied over a ten-month period. Total LAB was quantified using SYBR green qPCR. Seven hundred LAB isolates were characterized using microscopy, M13 RAPD genotyping and 16S rDNA sequencing. The highest and lowest LAB counts were detected at one week and ten months of age, respectively. Diverse LAB species were detected, whose identity and prevalence varied with age. The main isolates belonged to Limosilactobacillus reuteri, Limosilactibacillus fermentum, Lactobacillus johnsonni, Ligilactobacillus murinus, Ligilactobacillus salivarius, Limosilactobacillus mucosae, Lactiplantibacillus plantarum, Ligilactobacillus agilis, Lactobacillus acidophilus/amyolovolus, Pediococcus spp. and Enterococcus spp. Uniquely, L. reuteri and Pediococcus spp. were most common in pre- and peri-weaned goats, while Lactobacillus mucosae and Enterococcus spp. were predominant in goats one month and older. Based on RAPD genotyping, L. reuteri had the highest genotypic diversity, with age being a factor on the genotypes detected. This data may be relevant in the selection of age-specific probiotics for goats. The findings may also have broader implications by highlighting age as a factor for consideration in probiotic bacteria selection in other animal hosts.