Effects of Bentonite on Weight Gain, Feed Consumption, Blood Metabolites and Ruminal Protozoa in Dairy Calves

In order to ascertain the effects of addition of bentonite as a pelleting medium in the feed mixture for calves, fourteen 30d-old calves were randomly distributed into two equal groups (CON and EXP). From 30 to 120d of age the EXP group was fed a feed mixture containing 1.5% of natural bentonite while the CON group was fed the same pellets without added bentonite. Body weight was determined before and at the end of the trial. Feed intake was measured daily. Health status was monitored daily. Blood and rumen content samples were taken at 50 and 90d of experiment and analyzed for select parameters. The addition of bentonite had no effect (P > 0.05) on average daily gain, feed intake and health. Blood pH, total number and motility of ruminal protozoa in the EXP group were significantly (P < 0.001, P < 0.05 and P < 0.05; respectively) higher than in CON group at both the periods. At 120d of age the EXP calves had a significantly (P < 0.05, P < 0.05 and P < 0.01; respectively) higher serum total protein, albumin and triglyceride concentrations and lower iron and IGF-I (P < 0.05 and P < 0.01, respectively) concentrations than respective controls values. It is concluded that the use of pelleted feed containing bentonite tended to improve growth of calves as well as the activity of protozoa in the rumen. Additionally, the results indicate a positive influence of the function of hepatocytes concomitant to a reduction in serum iron and IGF-I concentrations.