The effects of organic selenium supplementation on the rumen ciliate population in sheep

The effect of selenium supplementation on the rumen protozoan population of sheep was demonstrated. Both the total and generic counts of rumen ciliates in sheep fed a diet with basal Se content (70 µg/kg dry matter) were compared to those of animals given feed supplemented with inorganic (disodium selenite) or organic Se (selenized yeast) (310 µg/kg dry matter). The genera ofEntodinium, Isotricha, Dasytricha, Ophryoscolex, Diploplastron andPolyplastron occurred in all sheep except for the control, in whichOphryoscolex was not observed. The population ofOphryoscolex caudatus f.tricoronatus was significantly higher in sheep supplemented with organic Se than in animals given inorganic Se (by 160 %). Supplementation of feed with selenized yeast induced significant growth in theDiploplastron population (by 63 %) while no change occurred in sheep given selenite. The populations ofDasytricha ruminantium andPolyplastron multivesiculatum were higher than control in both Se-supplemented groups. The ciliate population ofEntodinium spp. was not influenced by Se supplements. Our results suggest a protective effect of Se feed supplementation on the development of some rumen ciliate species in young ruminants.