BLOOD METABOLITE AND REGULATORY HORMONE CONCENTRATIONS AND RESPONSE TO METABOLIC CHALLENGES DURING THE INFUSION OF MIMOSINE AND 2,3-DIHYDROXYPYRIDINE IN ALPINE GOATS

Sixteen Alpine wethers (average BW 35 +/- 2 kg) were used to evaluate the effect of continuous 48-h intravenous infusions of saline (CON), mimosine (MIM; 200 mg.kg(.75).d(-1)), 2-hydroxy-3(1H)-pyridine (2,3-DHP; 200 mg.kg(.75).d(-1)), or MIM+2,3-DHP (100 mg of MIM plus 100 mg of 2,3-DHP.kg(.75).d(-1)) on hepatic function and selected blood metabolite and circulating hormone concentrations. Neither MIM nor 2,3-DHP affected plasma ammonia N, glucose, cortisol; or insulin concentrations over time (P > .10). Jugular plasma total protein concentration was greater in the MIM group (P < .07). Plasma triiodothyronine (P < .01) and thyroxine (P < .08) concentrations were higher in the goats receiving the MIM, 2,3-DHP, and MIM+2,3-DHP infusions than in the goats receiving the CON infusion. Plasma urea N concentration was decreased by MIM (P < .10) and MIM+B,S-DHP (P < .03) compared with the CON infusion. A Propionate Load Test was conducted at 24 to 28 h into the infusion to assess the toxins' effects on the liver's ability to increase circulating glucose concentrations in the presence of elevated propionate levels. The results indicated that neither 2,3-DHP nor MIM reduced the liver's ability to respond to a bolus dose of propionate (P > .10). Following a Urea Load Test, circulating ammonia N and glucose concentrations in the MIM, 2,3-DHP, and MIM+2,3-DHP treatments had lower peak values than that in the,CON treatment (P < .01). It is concluded that continuous short-term infusion of MIM and 2,3-DHP increased circulating thyroid hormone concentrations in goats and improved the goats' ability to detoxify a bolus dose of urea N without affecting its glucogenic capacity in response to elevated propionate levels.