The effect of paraformaldehyde on the fermentation quality and feeding value of ryegrass and lucerne silages

Abstract

SUMMARYCrops of perennial ryegrass and lucerne were each ensiled without additives and after the addition of paraformaldehyde to provide about 0·1, 0·2 or 0·4% HCHO/t crop fresh weight. The ryegrass and lucerne silages were offered ad libitum to sheep in separate experiments of identical design.All theryegrass silages were well preserved with low pH values, the level of butyric acid was very low and ammonia-N comprised less than 8% of total N. The lucerne silage made without additive had a pH of 5 and acetic acid comprised the major part of the total fermentation acids. Ammonia-N comprised over 12% of total N. All levels of paraformaldehyde addition restricted fermentation in both crops and led to an increase in the proportion of total N which was insoluble in hot water.Voluntary intake of organic matter (OM) was higher for the lucerne than for the ryegrass silages but digestible organic matter (DOM) intake was higher for the ryegrass. Intakes of OM and DOM were not significantly affected by paraformaldehyde treatment. The addition of paraformaldehyde significantly depressed apparent digestibility of OM and cellulose with the ryegrass but had less effect with the lucerne. Nitrogen digestibility was significantly depressed in both crops at all paraformaldehyde levels. Paraformaldehyde addition resulted in increased faecal N output and decreased urinary N, but retention of N was not significantly affected.The lack of response in feeding value to paraformaldehyde treatment may have been due to the relatively high intake and N retention of the untreated silages which were fairly well preserved.