Effect of treatment with formaldehyde, formic acid, and formaldehyde—acid mixtures on the chemical composition and nutritive value of silage

Abstract

Perennial ryegrass—clover-based herbage was made into direct cut silage in 10-tonne stacks. Formalin (40% w/v formaldehyde) was applied during harvesting at 3.3 and 5.6 litres per tonne of fresh grass and formic acid (85% w/w) at 1.8 litres per tonne, either alone or in combination with formalin. After 4½ months' storage the silages were fed to penned Romney sheep for 4 weeks. Addition of formic acid produced silages with lower contents of total volatile acids, especially butyric acid, and ammonia, and increased voluntary intake. This occurred both in the absence and in the presence of formaldehyde. In the absence of formic acid, formaldehyde treatment markedly reduced protein degradation but did not affect voluntary intake. The two combinations of formic acid and formaldehyde caused the greatest suppression of the silage fermentation, and voluntary intake tended to be higher on these treaments than where formic acid was applied alone. Wool growth rate was very low and was unaffected by any of the treatments.