Natalia Cecilia Maldonado and María Elena Fátima Nader-Macías*
Four different autochthonous calves’ strains: Lactobacillus johnsonii CRL1693, L. murinus CRL1695, L. mucosae CRL1696 and L. salivarius CRL1702 were evaluated by their resistance and survival to dairy farm conditions and were used to prepare probiotic fermented milk for young calves. The strains were previously isolated from calf’s faeces and selected by their beneficial properties. The resistance of the microorganisms to water, colostrum and raw milk was by using those of the environment of a dairy farm. Compatibility assays were performed to know if the strains can be combined in the final fermented product. For the elaboration of fermented milk, different inoculum, incubation times and acidifying capability of the strains were determined and also their survival and the maintenance of beneficial properties during storage at low temperature. Antibiotic resistance profiles were applied to differentiate the strains throughout the experiments. The results indicate that bacteria survive in colostrum (1, 3 or 5 days after calving) and water for 2 or 4 hours. All the strains grow in raw milk, and were compatible between them. The optimum fermentation time was 8 hours at 37°C, reaching 3.78 × 108 CFU/ml from an inoculum of 3 × 109 CFU of each strain in sterile milk. Surface properties as auto-aggregative and hydrophobicity patterns were maintained after the process. Bacteria remained viable during 30 days at refrigeration temperature at a concentration of 3.37 × 107 CFU/ml. The dose suggested is 10 ml of fermented milk prepared at the laboratory and stored at 4°C for younger animals. For older calves, a second fermentation in the farm is proposed to reach 3.94 × 106 CFU/ml. Animal experiments are being performed to determine the efficacy of the fermented milk for diarrhea prevention.
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