The digestion by cattle of grass silages made with no additive or with the application of formic acid or formic acid and formaldehyde

The aim of the experiment was to assess the effect of applying, at commercially recommended rates, formic acid or formic acid/formaldehyde at ensilage upon the subsequent digestion of the silages by cattle. Three wilted grass silages were made from perennial ryegrass ensiled at a DM concentration of 206 g kg−1 after a poor wilting period of 49 h without additive application and with application of 2.5 litres t−1 of formic acid or of 4.5 litres t−1 of a mixture of (gkg−1) 500 formic acid, 200 sulphuric acid and 200 formatin giving an application rate of 15 g formaldehyde kg−1 herbage crude protein (N × 6.25). The silages were fed to cattle equipped with rumen cannulae and duodenal re‐entrant cannulae. Results from analyses of silage composition and from the digestion of organic matter and N showed no major differences between silages. The efficiency of rumen microbial N synthesis, the rumen degradability of silage N (determined in vivo or in sacco) and in vivo digestion of individual amino acids were also unaffected by additive treatment. These results indicate that poor wilting conditions before ensilage restricted the effectiveness of additive treatment; the ineffectiveness of formaldehyde in reducing the rumen degradability of silage N may also have been related to the low rate of formaldehyde application.