Adaptation of pregnant ewes to an exclusive onion diet

A diet consisting entirely of cull onions fed to pregnant ewes produced Hei nz body hemolytic anemia in all sheep after 21 d. After 28 d of daily consu mption of 20 kg of onions/ewe, the anemia stabilized, and for the remaining 74 d the packed cell volume increased in the majority of sheep, although i t did not return to normal. Compared to control ewes fed an alfalfa and gra in diet, the onion-fed ewes had comparable body condition scores and fleece weights. There was no significant difference (alpha=0.05) in pregnancy or lambing rate, number of lambs born/ewe exposed, or number of lambs born/ewe lambing, Greater numbers of sulfate-reducing bacteria (Desulfovibrio spp) and more ruminal hydrogen sulfide were present in onion-fed sheep compared to controls. Although an average 27% reduction in packed cell volume and He inz body anemia developed in the onion-fed ewes, on the basis of this study it appears that pregnant ewes may be fed a pure onion diet with minimal de trimental effects. This adaptation to a pure onion diet is in part likely d ue to the apparent ability of the sheep's rumen to Quickly develop a popula tion of sulfate-reducing bacteria that decrease the toxicity of onion disul fides.