Abstract
Histamine concentrations of ruminal contents and plasma were determined in the cattle fed on a formula feed and rolled barley. Groups of three Holstein steers were each fed rice straw (0.6 kg) and concentrate rations (10 kg) consisting of 100% rolled barley in diet 1, 50% formula feed and 50% rolled barley in diet 2, 75% formula feed and 25% rolled barley in diet 3, and 100% formula feed in diet 4. Diet 5, a control, consisted of hay, haycube, formula feed (3kg) and rice straw. Each diet was fed for 4-5 weeks. Ruminal contents and plasma were sampled on the last day of each experimental feeding. The ruminal histamine levels at all sampling were significantly higher in diets 1, 2, 3, and 4 than in diet 5. The levels in diets 3 and 4 were markedly high and increased to the maximum immediately after feeding. The plasma histamine levels were significantly higher in diets 3 and 4 than in diets 1, 2 and 5 at perfeeding. Although there was no characteristic change in the plasma histamine level after feeding diet 1 or 2, the levels remarkably increased in diets 3 and 4. It was evident that ruminal histamine levels of steers fed on diets with higher contents of formula feed increased extremely after feeding. The increased plasma histamine concentration may have reflected the increased ruminal concentration.
