Equine fecal inoculum optimization in in vitro fermentation assays of dehydrated roughage

Abstract

This study evaluated the influence of coastcross hay substrate hydration and equine fecal inoculum dilution on the parameters of fermentation and microbiology in in vitro essays. A 2 × 2 factorial block design was used. The first factor was hydration of the coastcross hay substrate 12 h before incubation or at the time of incubation, and the second factor was the dilution of fecal inoculum with a nutrient solution in a weight: weight ratio of 1:1 or 1:3. Degradation of the dry matter (DM), organic matter (OM), and neutral detergent fiber (NDF) were evaluated at 24, 48, and 72 h. Microorganisms were counted 24 h after inoculation. The ammoniacal nitrogen concentration (NH 3-N), pH, and cumulative gas production were measured up to 72 h and adjusted by the non-linear Gompertz regression model. Hydration of substrate and time of incubation increased nutrient degradation of coastcross hay, as well as the final volume of gases and the concentration of Streptococcus spp. The 1:3 dilution increased the final pH and Streptococcus spp. concentration. The hydration of substrate did not have any effect on NH 3-N, Lactobacillus spp., cellulolytic, and total anaerobic bacteria concentrations. In addition, no effect of hydration was observed on the fermentation rate and the maximum fermentation time on the model used. The fermentation profile of the grass substrate is not affected by dilution, and, therefore, horse feces can be used as a source of inoculum in in vitro fermentation trials. Hydration increases the gas volumes and the nutrient degradation of grass hay, renders the lag phase time insignificant and, therefore, can be irrelevant in terms of fermentation model settings.

Impact of Storage Conditions on Equine Fecal Inoculum for Estimating In Vitro Digestibility

“…Microbial inoculum dilution and substrate hydration are other potential sources of variability, as substrate is hydrated when it reaches the cecum for fermentation. Franzan et al found that inoculum dilution does not alter fermentation, and substrate hydration increases the fermentation process, increasing nutrient degradation [ 8 ]. With large variations in microbial communities attributed to diet, collection time, and variation between individuals, microbial inoculum and its handling provides variability between runs and experiments.…”