| Abstrakt: |
Four trials were conducted to determine the relation of histamine, pH and lactic acid to sub-acute and acute acidosis.In a trial investigating adaptation to high concentrate feeds, wheat depressed feed intake and increased (P<.05) ruminal lactate. One percent NaOH plus 3% fat improved feed intake and reduced ruminal lactate levels on the wheat ration. Rumen fluid pH and histamine were not affected (P>.05) by grain source (wheat vscorn) or additives.In three lambs engorged with 3.2 kg of a ground corn diet, rumen pH declined from 6.77 to 4.74 after 4 hr and remained low until hour 60. There were two ruminal lactate peaks, one at 4 to 6 hr postengorgement and the second at 60 hour. Ruminal histamine was highest at 2, 10, 24 and 60 hr postengorgement.Infusing 50 ml of distilled water (control), 450 mg histamine, 15 g lactic acid or 400 mg histamine and 15 g lactic acid into the rumen of three sheep per treatment 1 hr postfeeding did not affect intake, but ruminal histamine disappearance was slower with the added lactic acid than when infused alone. Histamine disappeared more rapidly than lactic acid and both were removed more quickly than PEG.Trial 4 was the same as trial 3 except histamine and lactic acid levels were doubled (900 mg and 30 g, respectively). Addition of lactic acid or lactic acid plus histamine depressed (P<.05) intake, but histamine alone had no effect. Our results suggest that ruminal histamine does not play a major role in ruminant acidosis. |
