Histamine concentration in blood and contents of digestive tract in cattle overfed concentrate.

Changnes in histamine concentration were determined in the blood and contents of the digestive tract in cattle on concentrate overfeeding. Seven Holstein steers 15 weeks old were divided into two groups. One group of 4 steers (group C) was fed high concentrate and the other of 3 steers (group H) hay to serve as a control for l0 months. Histamine concentration was determined in plasma and ruminal contents collected at intervals of 2 or 3 weeks. Plasma histamine levels varied greatly in both groups during the experimental period. Their changes were almost the same in these groups. There was no significant difference in plasma histamine concentration between the two groups. The histamine level varied greatly in each group. It was more variable in group H than in group C. It was higher in group H than in group C and after l58 days of experiment. The histamine concentration was determined in the contents of the digestive tract collected from each steer at the time of slaughter. The histamine levels of the contents of the rumen and omasum were lower and those of the duodenum and ileum higher in group C than group H. There was no significant difference in the histamine concentration of the contents of the other portions of the digestive tract between both groups. The pH value of the contents of the digestive tract was generally smaller in group C than in group H. The pH value was especially small in the contents of rumen, omasum and duodenum.