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Occurrence and Disappearance of Ruminal Histamine and Tyramine¹

University of Kentucky^3,4,, Lexington 40506

Abstract

Three trials were conducted to study the occurrence and disappearance of histamine and tyramine from rumen fluid. Wethers were fed diets containing either no protein or 10% casein to study the effect of feed protein on ruminal amine levels at 0 and 4 hr postfeeding. There were no significant effects of time on any of the amines measured. Tyramine and tryp-tamine concentrations were higher (P<.01 and P<.05, respectively) when 10% casein was fed. Much of the amine concentration in rumen fluid appeared to result from the decarboxylation of dietary amino acids.

Histamine and tyramine were incubated in rumen fluid in vitro. During a 4-hr incubation period 65% of the histamine disappeared from rumen fluid of steers fed either grain or roughage. Tyramine disappearance from rumen fluid of a steer fed roughage was 5.4%, but no tyramine disappeared when incubated with fluid from a steer fed grain.

In trial 3, polyethylene glycol (PEG), histamine and tyramine were mixed into rumen fluid of four roughage-fed steers to measure amine disappearances in vivo. Apparent disappearances between .5 and 4 hr were calculated as 8.1%/hr for histamine and 8.2%/hr for tyramine. Comparing these disappearances in vivo with those observed in vitro, the disappearances of both amines in vivo appeared to be primarily due to microbial action rather than to absorption from the rumen.

¹ The investigation reported in this paper (77-5-198) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the director.

² Present address: Department of Agriculture, Southwest-Missouri State University, Springfield, MO 65802.

³ Department of Animal Sciences.

⁴ Appreciation is expressed to Mr. Walter Stroup for his statistical counsel.