The efficacy of different silage additives on different mixtures of white lupin and spring wheat was investigated in four separate trials. The bicrop was harvested 96 days (trials 1 and 2) and 110 days (trials 3 and 4) after sowing. For each maturity stage, two mixtures of white lupin and spring wheat were reformed in the ratios of 1:2 and 2:1 on fresh matter (FM) basis respectively. The crops were treated with formic acid (FA), sodium nitrite–hexamine mixture (NaHe) or homofermentative lactic acid bacteria (LAB). The control silage was made without additive. Additives were not able to improve the quality of white lupin–wheat silage in all trials, compared with untreated silage. The treatment with LAB showed good results only at the first stage of crop maturity with sufficient amounts of water‐soluble carbohydrate in the pre‐ensiling crops. The FA treatment showed elevated butyric acid levels in all trials, which suggests that the FA application level used (4 L t−1 FM, 100% FA) was insufficient to decrease pH enough for preventing the growth of clostridia and butyric acid fermentation. NaHe was the only additive that was able to inhibit the activity of clostridia in all trials.

The addition of hexamine did not improve silage quality compared with a solution of sodium nitrite. © 2018 Society of Chemical Industry.

Legumes are particularly susceptible to clostridial fermentation when ensiled because of their high buffering capacity and water-soluble carbohydrate contents. The aim of the study was to investigate if a sodium nitrite treatment (900 g t-1 herbage in fresh matter [FM]) impairs butyric acid fermentation of red clover-timothy-meadow fescue silage compared with formic acid-treated (4 l t-1 FM) and untreated silage. The sward was harvested after wilting at low dry matter (DM) (LDM, 194 g kg-1) and high DM (HDM, 314 g kg-1) concentrations and half of the herbage batches were inoculated with Clostridium tyrobutyricum spores before additive treatments. No butyric acid fermentation was observed in HDM silages probably because of the relatively high DM and nitrate contents of the herbage mixture. In LDM silage butyric acid was detected only in formic acid-treated silage, and the number of clostridia copies was higher in formic acid-treated than in sodium nitrite treated silage. Sodium nitrite treatment was superior to FA treatment in suppressing clostridial fermentation in the LDM silages.