The effect of formaldehyde or glutaraldehyde application to lucerne before ensiling on silage fermentation and silage nitrogen digestion in sheep

Siddons, R.C.; Arricastres, C.; Gale, D.L.; Beever, D.E.

British Journal of Nutrition 52(2): 391-402


ISSN/ISBN: 0007-1145
Accession: 006644174

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The primary growth of lucerne (Medicago sativa) was ensiled after treatment with either formic acid alone (4.1 liters/t; silage F) or with formic acid and either formaldehyde (30.5 g/kg crude protein (nitrogen .times. 6.25; CP); silage FF), glutaraldehyde (44.2 g/kg CP; silage FG) or a mixture of the 2 aldehydes at approximately half their individual application rates (silage FFG). Compared with formic acid alone, both formaldehyde and glutaraldehyde reduced protein breakdown and carbohydrate fermentation during ensiling. The extent of protein protection afforded within the silo was similar for the 2 aldehydes, whereas formaldehyde was more effective in restricing carbohydrate fermentation. The effect of treatment FFG on silage fermentation was confounded by the silo bag bursting and the development of a clostridial-type fermentation. All aldehyde treatments reduced silage soluble-N content but N disappearance when the silages were incubated in polyester bags in the rumen was high for all silages and reductions due to the aldehydes were small. Silage digestion was studied in 4 mature sheep each fitted with a rumen cannula and re-entrant cannulas in the proximal duodenum and distal ileum. The apparent digestibility or organic matter (OM) in the whole tract was reduced (P < 0.05) to a similar extent by both aldehydes, whereas rumen OM digestion was reduced (P < 0.05) more by glutaraldehyde than by formaldehyde. The effects on digestion appeared to be due to the action of the aldehydes on the foods rather than to any adverse influences of the aldehydes on the metabolism of the rumen microbes: although rumen ammonia levels were lower (P < 0.05) when the aldehyde-treated silages were given, rumen casein-degrading activity, the degradation of different feedstuffs when incubated in polyester bags in the rumen and microbial N flow at the duodenum did not differ (P > 0.05) between silages. All aldehyde treatments decreased (P < 0.05) the apparent digestibility of N in the whole tract. Silage N degradability in the rumen was also decreased (P < 0.05) from 0.82 for silage F to 0.67, 0.60 and 0.62 for silages FF, FG and FFG, respectively, and consequently non-ammonia-N (NAN) flow at the duodenum increased (P < 0.05). The aldehydes did not adversely affect the apparent digestibility of NAN in the small intestine, and net NAD absorption from the small intestine increased from 8.8 g/d with silage F to 11.4, 15.3 and 14.2 g/d with silages FF, FG and FFG, respectively. Both the decrease in N degradability in the rumen and the increase in net NAD absorption from the small intestine were greater (P < 0.05) with glutaraldehyde than with formaldehyde.