Studies On The Effect Of Soy Isoflavones On Ruminal Metabolism In Goat

The effect of soy isoflavones on the ruminal metabolism in goat were studied in this research which included three series:Series 1: Effects of soy isoflavones on ruminal metabolism in vitroMixed ruminal fluid from three female goats and artifical saliva(1:2) were incubated in anaerobic media for 12h in vitro with the power of peanut fodder(0.6 g) and concentrate(0.3 g) as the substrate. The soy-isoflavones(daidzein and genistein) were added to the incubation at different concentrations. The result showed that, when the concentration was 100mg/L, soy-isoflavones obviously affected ruminal metabolism, but results had diversity. Under this concentration, daidzein could increase NH₃-N, microbial protein(MCP) and all kinds of volatile fatty acids were obviously improved(P<0.05), A% decreased, P% increased. This result demonstrated daidzein promoted carbohydrates and nitrogen metabolism of ruminal microorganism. At the same concentration, genistein could increase NH₃-N appreciably, MCP was increased markedly(P<0.01), but total volatile fatty acid(TVFA) decreased, A% increased markedly(P<0.01), P% decreased markedly(P<0.01), this indicated that genistein promoted nitrogen metabolism but changed the fermentation pattern from P to A.Series 2: Effects of soy isoflavones on ruminal metabolism in vivoThree local female goats with permanent fistulae were used to study the effects of soy isoflavones(daidzein and genistein) on ruminal fermentation. Soy isoflavones were fed with diet and the levels of pH, NH₃-N, TDHA, MCP and VFAs were tested before feeding in the morning and every two hours from 2h to 10h after feeding in the morning. The result showed that: both of daidzein and genistein can affect the ruminal metabolism, but their effects had diversity. Daidzein can improve the activity of TDHA and the concentration of NH₃-N, MCP and all kinds of VFA, the proportion of propionate were enhanced. At 8h, compared with the control, the concentration of propionate were increased markedly (P<0.01). This demonstrated that daidzein promoted carbohydrates and nitrogen metabolism of ruminal microorganism. The result is same as that of in vitro. Genistein also can enhance the concentration of NH₃-N, MCP, and the activity of TDHA. But reduce the production of VFA, especially the acetate and propionate(P<0.01).This is consistent with the result of in vitro. But A% decreased, P% increased. The experimentations both in vitro and in vivo showed that genistein improved the nitrogen metabolism of ruminal microorganism and changed the fermentation pattern of rumen.Series 3: The metabolism of soy isoflavones in rumen and its effect on the concentration of 17β-estradiolThe feeding of goats and the the collection of samples are same as that of series 2. The change rule of soy isoflavones of the samples at different times were tested by HPLC, and the concentration of 17β-estradiol was tested by RIA. The result showed that, the soy isoflavones of the control phase were not detected, but there was 17β-estradiol in the rumen fluid. After feeding daidzein, there was equol in rumen fluid, and the concentration of equol was higher than that of daidzein, however, the genistein of the experiment phase wasn't detected. Daidzein and genistein all could improve the concentration of 17β-estradiol in rumen,but the effect of daidzein was more obviously(P<0.01).