Avaliação de modelos matemáticos de cinética de degradação ruminal

Abstract

The aim of this study was to identify the models which best fit the degradation profiles of some forages used in ruminant nutrition in order to obtain better estimates of the parameters that describe the kinetics of ruminal degradation. It were taken Three trials comparing four mathematical model (M1, M2, M3 and M4) degradation kinetics with different forages. In assay 1 ten forages were used, including three temperate grasses, four tropical grasses and three temperate legumes, all analyzed in triplicate (30 profiles). In assay 2 and 3 was evaluated oat IAPAR 126, subjected to four levels of nitrogen fertilization (12 profiles) harvest at four differents time (12 profiles). In addition to the modeling testing, chemical analysis were taken for possible correlations with the estimates of the parameters describing the kinetics of degradation. The way of the model fit to the data was verified by the corrected Akaike criterion (AICcr) the difference between the AICcr values (Δr), the probability of likelihood (Wr) and the relative likelihood (ERr). The M3 was the best fit to 72% of the profiles, the M1 to 22% and the M4 to 6%. There was a positive correlation between EE and LDA, EE and PB and between LDA and PB in the assay 3 and negative correlation between k2 and aFDN, k2 and k1 and between PB and k1. In trial 2 there was a positive correlation between k1 and k2 and negative correlation between PB and k1. The M3 results in estimates more credible parameters for forage with higher fiber and lower levels of non-fibrous carbohydrates and protein. The M1 has better quality forage adjust the gas production profiles with higher carbohydrate content not fibrous and lower lignin contente.