Effects of an inoculant containing a Lactobacillus buchneri that produces ferulate-esterase on fermentation products, aerobic stability, and fibre digestibility of maize silage harvested at different stages of maturity

Abstract

The aim of this research was to study the effects of a commercial inoculant containing Lactobacillus casei and Lactobacillus buchneri that produces ferulate esterase enzymes on fermentation products, aerobic stability, microbial status, dry matter (DM) losses, and digestibility of neutral detergent fibre (aNDF-D) of maize silages ensiled at four stages of maturity. The kernel milk line (ML) was used to time the forage harvest, and 1/6 ML, 2/5 ML, 3/4 ML and black layer (BL) were observed, for harvest stages I, II, III and IV, respectively. Chopped whole plant maize was untreated or treated with L. casei LC32909 and L. buchneri LN40177, which were applied to achieve a final application rate of 1×104cfu/g and 1.0×105cfu/g of fresh forage, respectively. The maize was ensiled in laboratory silos for 260 days before opening. The DM content, starch and ether extract concentrations and mould count increased, whereas water activity, nitrate, ash, water soluble carbohydrates (WSC) and crude protein (CP) contents progressively decreased with increasing maturity at harvest. The 24-h and 48-h aNDF-D were similar for harvest stages I, II and III, whereas they were the lowest in harvest stage IV. The effect of inoculation decreased with increasing DM content at ensiling, and the inoculum was ineffective at the last stage of maturity, probably due to the high epiphytic lactic acid bacteria (LAB) count, low water activity and low sugar content that could have negatively influenced the inoculation outcome. The inoculation lowered the lactic acid, yeast and mould counts and increased acetic acid, 1,2-propanediol, pH, DM losses and aerobic stability in the first three harvest stages, whereas no differences were observed between the treated and untreated silages harvested at the last stage of maturity. Regardless of the treatment, the yeast count fell under the detection limit and the aerobic stability of the silage increased to over 200h when the acetic acid content exceeded 25g/kg DM. Furthermore, the DM losses were closely correlated to the acetic acid production and increased to 80g/kg of DM in the treated silages harvested at the earliest stage of maturity. The potential milk production, estimated with MILK2006 model (Shaver et al., 2006, http://www.uwex.edu/ces/dairynutrition/spreadsheets.cfm), showed that the greater aNDF-D of the treated silage, which was observed in harvest stages I and III, did not counterbalance the higher DM losses attributable to the L. buchneri activity during ensiling, in terms of milk per Mg of original ensiled DM.