Relationships between blood metabolites and acidosis induced by feeding pelleted barley and wheat grains in dairy cows

It has been demonstrated that in acidosis condition due to transferring some metabolites from the rumen to blood, total metabolism could be changed. But relative change in blood metabolites and their relationship with behavior and performance of animal are not clear. The study investigated the relationship of the change in blood metabolites and the occurrence of acidosis to find easy to measure indicators.
Nine multiparous cows (650±56 kg BW; mean±SD) averaging 102±13 days in milk and producing 54±6 kg/d were randomly assigned to a triplicate 3 × 3 Latin square. During each 21-d period, cows were offered one of three total mixed rations that varied in diet fermentability. The three levels of diet fermentability were achieved by increasing the proportion of pellets containing ground wheat and barley in the dietary DM from 11.7%, to 23.3% and 35.0% by replacing ground corn grain. Each period had 14 d of adaptation and 7 d of sampling. Rumen pH and VFA profiles, feed intake, sorting index, chewing activity, milk production and efficiency, and blood metabolites (measured before and 4 h after morning feeding) were measured. The significant correlation between the blood metabolite and aforementioned variable were considered.
The result of this study showed the concentration of serum amyloid A measured 4 h after morning feeding was correlated with rumen pH (r=-0.45) and total VFA concentrations (r=0.51). Also, the concentration of aspartate amino transferase in the blood measured before morning feeding was significantly correlated with the proportion of rumen VFA. The metabolite along with alkaline phosphatase that measured 4 h after morning feeding were correlated with most variables of chewing activities (0.38≤r≤0.57), milk fat production (-0.61≤r≤-0.44) and feed efficiency (r=0.43). The concentration of cholesterol measured at 4 h post feeding was strongly correlated with most indicators of feed intake, milk production and its efficiency (0.57≤r≤0.77). Also, the concentration of glucose in the blood measured 4 h after morning feeding was correlated with feed intake at early time after morning feeding (r=-0.55). Moreover, the concentration of antioxidant in the blood measured before morning feeding was related to protein percentage (r=-0.55), milk production (r=0.57) and its efficiency (r=0.44). There were no clear relationships between blood metabolites and sorting index.
Overall, according to results it could be concluded that blood metabolites had a strong relationship with indicators of rumen acidosis and the concentration of alkaline phosphatase and aspartate amino transferase were a good indicators for predicting acidosis and relative consequences.