Effect of formaldehyde treatment on the chemical composition and nutritive value of silage

Untreated and formaldehyde (HCHO)‐treated silages were fed to sheep over a 6‐week period. Each silage was fed at two levels of energy intake; maintenance, when digestibility was measured, and ad libitum . Supplements of d‐l methionine were given by oral and intraperitoneal methods. The chemical composition and osmotic pressure of rumen fluid were determined on all treatments. Formaldehyde treatment reduced the apparent digestibility of nitrogen (N) by 10% (P < 0.01). The trend for this treatment to reduce the digestibility of dry matter and energy by 3‐4% did not attain significance. Oral or intraperitoneal supplementation with d‐l methionine did not affect the digestibility of dry matter, energy, or N. After feeding there was an increase in the concentration of ammonia and volatile fatty acids in rumen fluid and in the osmotic pressure of this medium. In post‐feeding samples of rumen fluid, the concentration of ammonia and the molar proportions of iso‐ and n‐valeric acids were reduced by HCHO treatment of silage, from which it was deduced that protein breakdown during the combined silage plus rumen fermentation processes was reduced by this treatment. Methionine supplementation had no effect on any of the rumen fluid parameters measured.