EFFECT OF HEXAMINE AND SODIUM-NITRITE IN COMBINATION WITH SODIUM BENZOATE AND SODIUM PROPIONATE ON FERMENTATION AND STORAGE STABILITY OF WILTED AND LONG CUT GRASS-SILAGE

Bale silage usually is made of unchopped or long cut grass. Long cut h erbage may be difficult to ensile, because of delay in the fermentatio n process. Long herbage reduces the density of silage and it is also d ifficult to distribute and mix additives in such material. The aim of the present study was to increase silage quality by using additives ba sed on a mixture of hexamine, i.e. hexamethylene-tetraamine (HMTA) and sodium nitrite (NaN) together with sodium benzoate (NaB) and sodium p ropionate (Nap), which are known to prevent growth of undesired fungi. The silage crop (344 g DM kg(-1); 153 g CP, 105 g ash, 90 g WSC, a bu ffering capacity of 270 mE and a ME value of 11.7 MJ per kg DM) consis ted of about 80% ryegrass (Lolium perenne) and 20% of meadow fescue (F estuca pratensis), was harvested by a self-loading wagon. Grass was en siled in 24 litres stainless steel containers. Silos were either close d immediately with a water-seal or aerated with 16 litres of air per 2 4 hours during the first 12 days of ensiling. Additives were added in concentrate form at low application rate, or diluted in water to 10 li tres ton(-1) fresh matter (FM). The following treatments were used (li tre ton(-1) FM): Untreated without an additive; Formic acid 3.4 litres ; KST 4.5 and 10 litres giving 400 g HMTA, 600 g NaN, 300 g NaB, 600 g NaP; KSQa 3 and 10 litres giving 500 g HMTA, 750 g NaN; KSQb 3 and 10 litres giving 1000 g HMTA, 750 g NaN; KSBa 10 litres giving 500 g HMT A, 750 g NaN, 1500 g NaB; KSBb 10 litres giving 1000 g HMTA, 750 g NaN , 1500 g NaB. The KSQ treatments, being a mixture of HMTA and NaN, red uced the growth of clostridium spores in the silage. When a mixture wa s weaker, but used in combination with sodium propionate and sodium be nzoate (treatment KST), the reduction was stronger. The number of clos tridium spores was reduced about 40 times compared with untreated sila ge and no butyric acid was detected. However, yeasts were more unaffec ted and reduced only after addition of 1500 g NaB (treatment KSB). The results also showed that an increased dose of HMTA from 400-500 g up to 1000 g ton(-1) FM did not improve silage quality, but stimulated mo uld growth. Butyric acid was positively correlated with clostridium sp ores, but the correlation was not strong r=0.53, (p <0.001). The relat ion between yeast counts and aerobic stability of silage became more o bvious r(2)=0.76 (p <0.001). Sodium benzoate reduced the number of yea sts down to 2.2-3.7 log CFU g(-1) FM and these silages were stable for 7 days or more. It is concluded that the activity of clostridia and f ungi in silage made from unchopped, wilted grass, is inhibited simulta neously when KSQ and NaB are used in appropriate doses.