Prognostic capacity assessment of a multiparameter risk score for aerobic stability of maize silage undergoing heterofermentative inoculation (Lactobacillus buchneri) in variable ensiling conditions

Abstract

The aerobic stability of silage is partially a consequence of its fermentative profile. The use of Lactobacillus buchneri (Lb) inoculant is widely adopted to promote a favourable quality of maize silage. Few studies investigated the effect of pre-ensiling composition on aerobic stability and the fermentative profile of silage. We evaluated the use of Lb in maize silage under variable ensiling conditions including differences in composition at harvest and exposure to air to test its possible effect on aerobic stability and fermentative profile, also by the means of a multiparameter prognostic risk score. Samples of maize from a single maize hybrid of late-ripening (n = 108) were collected in a single field area, at three maturity stages (MSe) and after three samples sealing delay periods (DLe) of air exposure (0, 6, 20 h). The heterofermentative inoculation with Lb was dispensed at three dosages (MXe: half dose, standard dose, double dose) and compared to a control (pure water). The combinations of MXe × MSe × DLe, were repeated three times. The 108 samples were ensiled in a 21 L bucket for 60 days, and analysed for the fermentative profile, dry matter (DM), and DM recovery (DMr) at three times (OTe: at the silos opening, after 48 h, after 96 h). The aerobic stability of the silage was considered as the outcome for the survival analysis by the means of an Akaike's information criterion backward Cox model (AIC-Cox), and the end-point was the event (defined as the aerobic instability). Concerning the main fermentative traits of post-ensiled maize (pH, ammonia, mannitol, ethanol, lactic, acetic, propionic, and butyric acid), and the DMr, we found effects (P < 0.05) for the use of inoculant (except for DMr, mannitol, ethanol, and butyric acid), for the maturity stage (except for ammonia), and the sealing delay (except for mannitol, lactic, and butyric acid). In the AIC-Cox model, the lignin (sa) and ADF were used as predictors, and the concordance index was 0.75 (P = 0.0001). Based on the AIC-Cox model, drawing a nomogram, it was possible to assess the probability of aerobic stability of maize silage through a prognostic score which allows a fast and easy risk stratification of maize using the pre-ensiled composition as predictors.