Effect Of Sources And Levels Of Selenium On In Vitro Ruminal Fermentation And Nutrient Degradation Of Dairy Cows

In vitro anaerobic fermentation technology was used in this experiment in order to research the effects of different sources and levels of selenium on rumen fermentation and nutrient degradation of dairy cows, which will provide theoretical basis for selecting suitable source and appropriate dosage of selenium in dairy cow diets.The experiment was divided into2parts. Trial1was a3×4factorial arrangement with a total of12groups, and the first fator was the source of selenium (Sodium selenite, Selenium methionion, Selenium yeast), and the second factor was selenium level added to incubating system (0,0.1,0.2and0.3μg per milliliter medium). In vitro ruminal fermentation fluid samples of each group were collected at the time point of3h,6h,9h,12h,24h48h after in vitro batch culture. The purpose was to study the effects of different sources and levels of selenium on in vitro ruminal fermentation by measuring ruminal fermentation parameters.Trial2with similar design to the trial1was conducted to research the effects of different sources and levels of selenium on nutrient degradation in in vitro rumen of dairy cows.The preliminary results were as following with this experimental conditions:(1) Supplementing organic selenium (methionine selenium, selenium yeast)could increase significantly BCP concentration of in vitro culture fluid (P<0.05), and selenium yeast had the best effect. Selenium sources had no significant effects on pH value, the concentration of NH3-N, Se, acetic acid, propionic acid, butyric acid and C2/C3of in vitro culture fluid (P>0.05), but pH value with adding selenium yeast had a tendancy to be reduced, and the others had an increasing tendancy.(2) Adding0.3μg/mL of selenium in In vitro culture medium could improve the concentration of NH3-N, BCP,Se, acetic acid, propionic acid, butyric acid and reduced C2/C3significantly (P<0.05). Andingg0.1μg/mL and0.2μg/mL selenium also had the better promoting effect.(3) Adding sodium selenite, methionine selenium, or selenium yeast in in vitro culture medium had no effects on DM, CP, NDF, ADF degradation rate (P>0.05), but selenium yeast had the best effect, and methionine selenium was the second.(4) With the increasing selenium added to in vitro culture fluid (Oμg,0.1μg,0.2μg, 0.3μg/mL selenium), nutrient degradation rate had an increasing tendancy. In vitro culture medium supplemented with the level of0.2μg/mL,0.3μg/mL selenium could improve DM, CP, NDF, ADF degradation rate significantly (P<0.05), and adding0.3μg/mL of selenium was the best.(5) All the indicators showed that adding the appropriate amount of selenium could improve rumen fermentation and nutrient degradation.Selenium yeast was the best selenium sources, and0.3μg/mLselenium had the best effect.