PSXII-36 Modelling in vitro gas production kinetics of fresh alfalfa incubated with inocula from five ruminant species

Abstract

Abstract The objective was to identify the non-linear model with the best fit for cumulative gas production from fermentation of fresh alfalfa, with or without tannin extract, incubated with rumen fluid from five different species of ruminants. Fifteen animals (Taurine and Zebuine cattle, water buffaloes, sheep and goats) were used as inoculum donors. During incubation, 500 mg of fresh alfalfa, with or without 150 mg of acacia tannin extract, were used as substrate in the semi-automated gas production technique. Experimental design was completely randomized in a factorial arrangement with five inoculum sources (ruminant specie) and two treatments (with or without tannin extract). We used the PROC NLMIXED to fit ten mathematical models and the best one was chosen based on the lowest AIC and MSE and highest R2. Lastly, the best model was validated using the cross validation technique. The model with the best fit was the Groot model (AIC 1255.5; MSE 174.01; R2 0.9496) comparatively to others methods and the most part of error is from random effect (97.7%). Tannin inclusion reduced parameters potential gas production (A) and time to produce half of total gas production (T1) (P > 0.0001); however, no difference was observed on the gas production rate (k) (P > 0.1181). When no tannin was added, differences between the two cattle category were observed. Comparing water buffaloes’ inoculum with Taurine inoculum, no differences were observed for “A,” however, this parameter differed among water buffaloes and Zebuine cattle. In conclusion, Groot model had the best fit on in vitro bioassay with alfalfa substrate and treated or not with tannin extract. The tannin extract reduced the potential gas production; however, it did not change the gas production rate. For evaluation of alfalfa by cumulative gas production technique, the potential gas production was changed by using different animal categories as inoculum donor.