Dissertação
Função de bactérias e fungos ruminais na degradação de forragens in vitro
Fecha
2021-02-23Autor
Rösler, Dérick Cantarelli
Institución
Resumen
The study was conducted to evaluate the interactive role of bacteria and fungi on the
degradation of forages C3 and C4 in vitro. Dry and ground (1 mm) samples of Cynodon
spp. (Tifton 85) and Lolium multiflorum Lam. (Azevém) were weighed (1.5 g) in triplicate
in 160 mL flasks and incubated in vitro for 48 h in medium (50 mL buffer + 50 mL
ruminal inoculum) containing or not antimicrobial substances. A mixture of penicillin,
chloramphenicol and streptomycin (500 mg/L each) was used as an antibiotic and
cycloheximide (50 mg/L) was used as antifungal. In vitro fermentations were carried out
anaerobically in water-bath slow-stir system at 39 °C. The treatments were: antibiotic
(F), antifungal (B), positive control (BF+, without antimicrobials) and negative control
(BF-, with antimicrobials). Three replicate assays were performed for each forage and, in
each assay the gas volume was measured at 3, 6, 9, 12, 24, 36 and 48 hours of
incubation. For 24, 36 and 48 hours there was a three replicate of flasks of each
treatment, which the solid residue had its DNA extracted. The DNA of bacteria and
rumen fungi at each treatment and hour was quantified by Polymerase Chain Reaction
real time (qPCR) analysis. The enzymatic activity of each treatment, at each time, was
evaluated through incubation with xylan and subsequent analysis of reducing sugars by
the Somogyi-Nelson method. Data of cumulative gas production in each flask in each
assay was fitted to an one-pool logistic model which generated three kinetic parameters:
total gas production (V, mL), rate of gas production (Kd, %/h) and lag time (L, hours).
The data were analyzed using the GLM procedure of the SAS and the means compared
using the T Student test, with a significance value of 5%. Ruminal bacteria had the
greater role in the degradation of forages. For tifton 85, fungi and bacteria interacted
synergistically and allowed greater degradation and bacterial adherence. There was
poor degradation and adherence of fungi to azevém, and bacteria was the main
responsible for the adhesion and degradation of this forage. Greater enzymatic activity
was observed for tifton 85, compared to azevém. The interaction of bacteria and fungi
tends to have greater enzymatic activity and there was no difference between isolated
populations about the production of enzymes. The results of this study contribute to a
better understanding of the activity of fungi in the rumen, as well as its interaction with
the bacterial population on the degradation of forages