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

Abstract

Abstract Ryegrasss-white clover pasture was conserved as silage, as hay made at the same time as silage (early hay), and as hay cut 4 weeks after silage (late hay). The silage was either untreated or treated with formaldehyde alone, formaldehyde + formic acid, or formaldehyde + sulphuric acid. After 4 months' storage the six diets were fed to penned Romney wethers for 6 weeks. Mean daily voluntary intakes of digestible organic matter (DOM) in g/kg W0.75 were untreated silage 18.2, formaldehyde silage 25.0, formaldehyde + formic acid silage 29.6, formaldehyde + sulphuric acid silage 26.4, early hay 36.2, and late hay 24.2. The generally low intakes are considered to be due to heavy sheep in fat condition Leing used. Organic matter digestibility was unaffected by any of the silage treatments, but early ilay reduced it by 4 percentage units. Apparent nitrogen digestibility was markedly reduced by all three silage treatments and by making hay. The amount of digestible energy (DE) /unit DOM was unaffected hy making either hay or formaldehyde + formic acid silage, but was increased respectively 3.5, 13.5, and 8.5% in untreated, formaldehyde, and formaldehyde + sulphuric acid silage. This resulted in DE intakes being similar for all three treated silages. Untreated and formaldehyde-treated silages had the lowest temperatures after opening, although voluntary intakes on both declined with time. Adding either formic or sulphuric acids to formaldehyde increased stack temperatures on exposure to air but, surprisingly, prevented the decline in intake with time. Wool growth and fibre diameter were lowest for untreated silage, highest for early hay, and intermediate and of similar magnitude for the other treatments. Wool synthesised per unit of DE intake did not differ among the silages, but was higher on hay than on silage diets.