EFFECTS OF GRADED-LEVELS OF BENTONITE ON SERUM CLINICAL PROFILES, METABOLIC HORMONES, AND SERUM SWAINSONINE CONCENTRATIONS IN LAMBS FED LOCOWEED (OXYTROPIS-SERICEA)

To determine which clay minerals have the potential to bind swainsonin e, an in vitro screening procedure was conducted. Twenty compounds wer e screened in one replicated in vitro trial. A commercially available bentonite bound approximately 10% swainsonine and was chosen for use i n a subsequent lamb feeding trial. Twenty fine-wool lambs (30.5 +/- .7 kg) were assigned to one of five treatments (four lambs/treatment). T reatments included 1) positive control, 100% sorghum sudangrass hay, 2 ) 85% sorghum sudangrass:15% locoweed (Oxytropis sericea, 430 ppm [DM basis] of swainsonine) + 0 g of bentonite, 3) Treatment 2 + 14 g of be ntonite, 4) Treatment 2 + 28 g of bentonite, and 5) Treatment 2 + 42 g of bentonite. Lambs were fed the experimental diets for 35 d and were then fed the positive control diet for an additional 21 d. Lambs were weighed and blood was collected via jugular venipuncture weekly from d 0 through 56. On d 35, additional blood samples were collected 1, 2, 4, and 8 h after feeding. Weekly blood samples were analyzed for seru m clinical chemistry profiles, and additional blood samples collected on d 35 were analyzed for serum metabolic hormones and serum swainsoni ne concentrations. Within 1 wk, serum alkaline phosphatase and glutami c oxaloacetic transaminase activities increased markedly (P < .05) in lambs fed locoweed. Serum insulin, growth hormone, and prolactin conce ntrations were not affected by feeding locoweed, but serum triiodothyr onine and thyroxine concentrations were decreased by approximately 50% (P < .05) in lambs fed locoweed. Serum swainsonine concentrations wer e not detected in lambs fed the positive control diet and ranged from 144 to 235 ng/mL in lambs fed locoweed. Overall, serum profiles, metab olic hormone concentrations, and serum swainsonine concentrations indi cated that the bentonite (up to 42 g daily) was ineffective in allevia ting locoweed toxicosis.