J. Jouany, P. Thivend
Aug 1, 1986
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0
Influential Citations
41
Citations
Journal
Animal Feed Science and Technology
Abstract
Abstract The effect of avoparcin on the degradability of eight proteins, chosen for their different solubilities (corn steep, lupin seed, peanut cake, rapeseed cake, soya bean cake, corn feed, fishmeal and corn fiber) was studied in an in vitro system which allowed the main digestion end products formed in the rumen (VFA, gases, NH 3 -N and nitrogen incorporated in bacteria) to be defined. Avoparcin caused a decrease in the degradability of the different proteins. The decrease was largest with the highly soluble proteins. Degradability in the presence of avoparcin ( Y ) was linearly related to the control degradability ( X ) in the equation: Y = 0.650 X + 4.423. Avoparcin was found to reduce the amount of nitrogen incorporated in bacteria. This decrease was relatively constant despite the different types of nitrogen used (ammonium sulfate alone or added to proteins). In fermenters containing (NH 4 ) 2 SO 4 as the only source of nitrogen, the addition of avoparcin lowered the VFA production by 20% mainly in acetate and butyrate whilst propionate production was not modified. VFA production, which was increased when protein was added to the fermenters, was not changed by the presence of avoparcin. The slight decrease in acetate and butyrate production was compensated for by a slight increase in propionate production in the fermenters containing protein nitrogen. Gas production was reduced by avoparcin (10–20%). Gas analysis carried out on fermenters containing (NH 4 ) 2 SO 4 as the only source of nitrogen showed a large decrease in methane production with avoparcin. Microbial synthesis efficiency, expressed as the ratio “microbial nitrogen incorporated per mole of VFA produced”, was lowered by avoparcin. This decrease in fermenters containing proteins was largely due to a lower microbial synthesis since VFA production was not modified. These results can be explained if avoparcin uncouples fermentation, as previously shown with monensin. Although avoparcin has no effect on ion-transport, it produces the same changes in the pattern of fermentation and protein degradability as the ionophores (monensin-lasalocid). It improves the metabolic utilization of diet energy and protein degradability.