Characterization of toxicosis in sheep dosed with blossoms of sacahuiste (Nolina microcarpa)1

Abstract

To characterize more fully sacahuiste (Nolina microcarpa Watson) toxicosis in sheep and to evaluate benefits of supplemental Zn, sheep were dosed intraruminally with sacahuiste blossoms. In Trial 1, eight fine-wool sheep (47 +/- 2 kg BW) were fed alfalfa hay at 1% of BW daily and dosed intraruminally with inflorescences amounting to 1% of BW daily, in three portions per day, for 10 d. Four sheep were dosed intraruminally with aqueous ZnSO4 (30 mg of Zn/kg BW) daily for 3 d before initial sacahuiste dosing and on alternate days thereafter, and four sheep were untreated with Zn. Toxicosis was evident within 24 h after initial sacahuiste dosage, involving inappetence, depression, hypokalemia, hypophosphatemia, hyperbilirubinemia, and elevated serum enzymes (alkaline phosphatase, creatine kinase, lactate dehydrogenase, aspartate aminotransferase, and gamma-glutamyl transpeptidase). One sheep (untreated with Zn) died on d 3. Aqueous ZnSO4 alleviated inappetence and suppressed elevation of serum urea N and creatinine but did not suppress other changes in serum clinical profiles. In Trial 2, sacahuiste inflorescences were ruminally dosed into 12 fine-wool wethers (29 +/- 2 kg BW) in amounts equalling 0, .25, .50, .75% of BW per day, and chopped alfalfa hay was provided at 1.75% of BW per day for 14 d. Sacahuiste inflorescenses dosed at .75% of BW elicited severe toxicosis within 24 h, and dosage at .50 or .25% of BW per day increased (P = .12) serum bilirubin. Ruminal fluid pH, mean particle retention time, and particulate passage rate were not affected (P > .10) by sacahuiste, but ruminal fluid passage rate increased 1.6-fold (P < .10) and ruminal fluid volume decreased by 60% (P < .10) in sheep given inflorescenses amounting to .50% of BW daily. Sacahuiste inflorescenses dosed intraruminally at .75% of BW per day elicited ruminal impaction with severe hepatotoxicosis, and dosages amounting to .50% or .25% of BW per day caused similar trends.