For the sake of examining the relationship between blood concentrations of lactic acid (LA) and ammonia (NH
3) and rumen condition, 25 Holstein dairy cows were divided into 3 groups on the basis of diet: normal (N), high starch (S), and high protein (P). In the S group, the number of protozoa and their motility in rumen fluid decreased remarkably after feeding. Two hours after feeding, rumen-fluid concentrations of both D-LA and L-LA increased. Rumen-fluid pH, however, dropped after feeding. Correlation between D-LA and L-LA concentrations in both blood and rumen fluid was observed. In the P group, 23 hours after feeding, NH3 concentration in the rumen fluid increased remarkably. In the N and S groups, however, concentration in the rumen fluid decreased 4 hours after feeding. Correlation of NH
3 concentration in both rumen fluid and blood was observed 4 hours after feeding. Blood LA and NH3 concentrations reflect protein intake and digestion in dairycow rumen.
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