Effect of Different Levels of Milk Thistle (Silybum Marianum) in Diets Containing Cereal Grains with Different Ruminal Degradation Rate on Rumen Bacteria of Khuzestan Buffalo

The objective of this study was to investigate the effects of diets containing different levels of milk thistle (0, 100 and 200 g/kg dry matter) and grains (barley and corn) with different rumen degradation rates on rumen bacteria and whole rumen microorganisms (WRM) of Khuzestan buffalo. The gas production (GP) technique, two steps digestion and specific bacteria culture medium methods were used for this purpose. The rumen fluid was taken from two fistulated buffaloes. The results of GP potential of experimental diets by WRM were not significantly different, however in both basal diets GP increased by increasing the level of milk thistle (P>0.05). The highest amount of GP in diet based on barley and corn was for diets containing 200 and 100 g milk thistle, respectively. Rate of GP by WRM was significantly different (P<0.05), so that in both basal diets at the level of 100 g milk thistle had the highest GP rates. Potential and rate of GP of diets by buffalo rumen bacteria was not significantly different (P>0.05). In two-steps digestion method us-ing of different levels of milk thistle in diets (based on barley and corn) had no negative effect on the di-gestibility of nutrients by WRM (P>0.05). In barley-based diet adding milk thistle was numerically in-creased dry matter and neutral detergent fiber (NDF) digestibility compared with the control (P>0.05), while in the corn-based diet dry matter and NDF digestibility were reduced (P>0.05). The digestibility of dry matter by bacteria in corn-based diet was significantly reduced compared with the control (P<0.05). Nutrient digestibility of experimental diets by bacteria in the specific bacteria culture did not be affected by milk thistle in diets (P>0.05). Therefore, results provided here suggest that milk thistle could be used up to 20% of buffalo's diet without any negative effect on digestion and fermentation characteristics by WRM and bacteria.