THE EFFECT OF SULFATE ON THIAMINE-DESTROYING ACTIVITY IN RUMEN CONTENT CULTURES INVITRO

The effect of sulphur on thiamine-destroying activity was studied in n ative or thiamine-spiked rumen content cultures. The treatments consis ted of water [control (Ctrl)], sodium chloride (NaCl) and sodium sulph ate (Na2SO4). A net gain (relative to 0 h) of thiamine in native cultu res was observed for at least 48 h at levels of S ranging from 0.25 to 8 mg S added per ml of the culture and also in the Ctrl and respectiv e NaCl cultures. However, after 48 h of incubation thiamine concentrat ion was lower (p < 0.05) in native cultures treated with Na2SO4 relati ve to Ctrl and NaCl treatments. There was a linear (p < 0.03) time tre nd indicating an effect of Na2SO4 over time on changes in thiamine con centration in native rumen cultures. In thiamine-spiked rumen content cultures, the cultures treated with Na2SO4 produced higher (p < 0.05) thiamine-destroying activity. There was no effect of cation (Na) on th iamine-destroying activity. Initial heat treatment of thiamine-spiked cultures inactivated part of the thiamine-destroying activity. There w ere no differences among treatments in heat treated cultures. It is co ncluded that sulphate increases thiamine-destroying activity in the ru men content and the destructive mechanism involves thermolabile factor (s), however, the ruminal synthesis of thiamine is not affected by sul phate.