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Modulation of animal gut microbiota is a prominent function of probiotics to improve the health and performance of livestock. In this study, a large-scale survey to evaluate the effect of lactic acid bacteria probiotics on shaping the fecal bacterial community structure of feedlot cattle during three experimental periods of the fattening cycle (163 days) was performed. A commercial feedlot located in northwestern Argentina was enrolled with cattle fed mixed rations (forage and increasing grain diet) and a convenience-experimental design was conducted. A pen (n = 21 animals) was assigned to each experimental group that received probiotics during three different periods. Groups of n = 7 animals were sampled at 40, 104 and 163 days and these samples were then pooled to one, thus giving a total of 34 samples that were subjected to high-throughput sequencing. The microbial diversity of fecal samples was significantly affected (p < 0.05) by the administration period compared with probiotic group supplementation. Even though, the three experimental periods of probiotic administration induced changes in the relative abundance of the most representative bacterial communities, the fecal microbiome of samples was dominated by the Firmicutes (72–98%) and Actinobacteria (0.8–27%) phyla, while a lower abundance of Bacteroidetes (0.08–4.2%) was present. Probiotics were able to modulate the fecal microbiota with a convergence of Clostridiaceae, Lachnospiraceae, Ruminococcaceae and Bifidobacteriaceae associated with health and growth benefits as core microbiome members. Metabolic functional prediction comparing three experimental administration periods (40, 104 and 163 days) showed an enrichment of metabolic pathways related to complex plant-derived polysaccharide digestion as well as amino acids and derivatives during the first 40 days of probiotic supplementation. Genomic-based knowledge on the benefits of autochthonous probiotics on cattle gastrointestinal tract (GIT) microbiota composition and functions will contribute to their selection as antibiotic alternatives for commercial feedlot.

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As a first step for the use of probiotics in a formula for cattle, it is required to have available low-cost culture medium(s) and efficient production conditions for the growth of probiotic bacteria and high production of cell biomass. De Man-Rogosa-Sharpe (MRS) medium, used frequently for Lactic acid bacteria (LAB) contains adequate ingredients for their growth, but is very expensive for industrial application. The nutrients required for LAB growth are strain-dependent. In this work, traditional culture media were evaluated omitting and/or modifying ingredients in their composition, as carbon or nitrogen source, on the basis of their low-cost industrial waste, to select those supporting the most efficient growth. The results showed that the formulation of culture media containing fructose (0.5%) and molasses (1.0%) was better for the growth and production of cell biomass for all the strains assayed, except Lactobacillus gasseri CRL1421 growing in 1.5% corn syrup. FM902 yeast extract at concentrations between 1.5%-2.5% was the most adequate for most of the strains. The LAB grown in the designed media maintained the beneficial properties for which they selected. The use of the culture media designed to produce biomass decrease production costs, which is an important step for the feasible industrial production of probiotic pharmaceuticals.

Modulation of animal gut microbiota is a prominent function of probiotics to improve the health and performance of livestock. In this study, a large-scale survey to evaluate the effect of lactic acid bacteria probiotics on shaping the fecal bacterial community structure of 126 feedlot cattle during three experimental periods of the fattening cycle (163 days) was conducted. A feedlot industry located in northwestern Argentina was enrolled with cattle fed mixed rations (forage and increasing grain diet). High-throughput sequencing (HTS) of 16S rDNA amplicons was applied to characterize the fecal microbiota and explore its modulation as affected by the administration of five probiotic groups and experimental administration periods. The microbial diversity of fecal samples was significantly affected (p < 0.05) by the administration period compared with probiotic group supplementation. The fecal microbiome of samples was dominated by the Firmicutes (72-98%) and Actinobacteria (0.8-27%) phyla, while a lower abundance of Bacteroidetes (0.08-4.2%) was present. At the family level, probiotics were able to modulate the fecal microbiota with a convergence of Clostridiaceae, Lachnospiraceae, Ruminococcaceae and Bifidobacteriaceae associated with health and growth benefits as core microbiome members. Metabolic functional prediction comparing experimental administration periods showed an enrichment of metabolic pathways related to complex plant-derived polysaccharide digestion as well as amino acids and derivatives during the first 40 days of probiotic supplementation. Genomic-based knowledge on the benefits of autochthonous probiotics on cattle gastrointestinal tract (GIT) microbiota composition and functions will contribute to their selection as antibiotic alternatives for the feedlot industry.