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.
1996
Laettemaee P. | Lingvall P.
Bale silage usually is made of unchopped or long cut grass. Long cut herbage may be difficult to ensile, because of delay in the fermentation process. Long herbage reduces the density of silage and it is also difficult to distribute and mix additives in such material. The aim of the present study was to increase silage quality by using additives based on a mixture of heaxamine, i.e. hexamethylene-tetraamine (HMTA) and sodium nitrite (NaN) together with sodium benzoate (NaB) and sodium propionate (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 buffering capacity of 270 mE and a ME value of 11.7 MJ per kg DM) consisted of about 80% ryegrass (Lolium perenne) and 20% of meadow fescue (Festuca pratensis), was harvested by a self-loading wagon. Grass was ensiled in 24 litres stainless steel containers. Silos were either closed immediately with a water-seal or aerated with 16 litres of air per 24 hours during the first 12 days of ensiling. Additives were added in concentrate form at low application rate, or diluted in water to litres ton-1 fresh matter (FM). The following treatments were used (litre 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 HMTA, 750 g NaN, 1 500 g NaB; KSBb 10 litres giving 1 000 g HMTA, 750 g NaN, 1 500 g NaB. The KSQ treatments, being a mixture of HMTA and NaN, reduced the growth of clostridium spores in the silage. When a mixture was weaker, but used in combination with sodium propionate and sodium benzoate (treatment KST), the reduction was stronger. The number of clostridium spores was reduced about 40 times compared with untreated silage and no butyric acid was detected. However, yeasts were more unaffected and reduced only after addition of 1 500 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 growth. Butyric acid was postively correlated with clostridium spores, but the correlation was not strong r=0.53 (p less than 0.001). The relation between yeast counts and aerobic stability of silage became more obvious r2=0.76 (p less than 0.001). Sodium benzoate reduced the number of yeasts 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 fungi in silage made from unchopped, wilted grass, is inhibited simultaneously when KSQ and NaB are used in appropriate doses.
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