Anaerobic rumen fungi: Probiotic for dairy cows?

Isabel Gigli, Facultad de Agronomía, Universidad Nacional de La Pampa, Argentina

Mario Calafat1, Aníbal Pordomingo2, and Isabel Gigli1
1. Facultad de Agronomía, Universidad Nacional de La Pampa, Argentina;
2. Instituto Nacional de Investigación Agropecuaria, EEA Anguil, Argentina

Among volatile fatty acids (propionate, butyrate and acetate) produced by ruminal microflora, propionate is the one that directly impacts total milk production. Once absorbed by ruminal papilla, propionate is transformed into glucose in the liver, and then used in the mammary gland to synthesize lactose. Changes in the cows’ diet and subsequent changes in the ruminal microflora could affect volatile fatty acids production. Ruminal microflora consists of bacterial protozoa, methanogenic archaea and anaerobic fungi. These anaerobic fungi penetrate the cellulose material and therefore collaborate with the bacterial degradation. As a first step in evaluating the possible use of ruminal fungi as a probiotic, we studied the kinetics of dry matter and volatile fatty acids production of Panicum Vigatum in two development stages (senescence and green). In previous studies, we determined that the optimal antibiotic combination and concentration to obtained an enriched fungi culture was 0.2 mg/ml of Streptomycin plus 1.25 mg/ml of Penicillin. Briefly, whole rumen content, kindly provided by INTA (National Institute of Agricultural Technology), from eight different cows adapted to natural pasture was collected. At the laboratory, these samples were strained through a double-layered cloth, pooled, and kept under CO2 flushing. Previously, Panicum Vigatum—senescence and green leaves—were cut in 5mm diameter discs by a cork borer punched and cultured in the presence of antibiotic, as previously described, in anaerobic condition. Control samples were cultured in similar condition but without antibiotics. Neocallimastix fungi were identified by light microscopy of preparations stained with lactophenol blue solution. Dry fiber matter disappearances and volatile fatty acid concentrations were determined at 48 and 160 hours. In the senescence leaves samples, there was no statistical significance in the percentages of dry fiber matter disappearances or on the volatile acid concentrations between the two groups (control and enriched fungi culture). On the contrary, when green leaves were inoculated, the dry fiber disappearance and the concentration of propionate were higher (p ≤ 0.05) in the enriched fungi group at 48 hours (control 3.3 nmol/l ± 0.07 vs enriched fungi 4.1 nmol/l ± 0.45) and at 160 hours (2.5 nmol/l ± 0.07 vs 3.0 nmol/l ± 0.45). We conclude that ruminal anaerobic fungi favored propionate production when green leaves are inoculated. These preliminary results
encourage us to continue our studies to determine if anaerobic ruminal fungi could function as probiotic to increase propionate concentration in the rumen and consequently to produce a positive impact on milk production.

The authors acknowledge the financial support from POIRe (Proyectos Orientados de Investigación Regional) 29014-05-UNLPam and Weizur SRL for funding this project.

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