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United States Department of Agriculture

Agricultural Research Service


item Reed, Meredith
item Obeidat, Belal
item Strickland, James
item Krehbiel, Clinton
item Taylor, Joshua - Bret
item Loest, Clint
item Bell, Greg

Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2003
Publication Date: 7/1/2003
Citation: Reed, M.M. Obeidat, B.S., Strickland, J.R., Krebiel, C.R., Taylor, J.B., Loest, C.A., Bell, G.S. Effects of swainsonine on digestion in wethers consuming locoweed. Western Section of Animal Science Proceedings. 2003. v 54. p. 108-111.

Interpretive Summary: In the western United States, locoweed poisoning results in substantial economic losses each year. Although the clinical signs of toxicity as well as the effects on livestock productivity are well defined, limited information is available describing the affects of locoweed on nutrient digestion in the grazing animal. The objective of this study was to assess the effects of swainsonine on digestion of sheep (wethers) consuming locoweed. Locoweed was fed to sheep for 23 days at levels known to induce varying degrees of locoweed toxicity in grazing animals (e.g., sheep, cattle). At the conclusion of the trial, locoweed toxicity was observed, but digestion was not altered in the sheep consuming locoweed.

Technical Abstract: A trial was conducted to study the effects of swainsonine on digestion. Mixed breed wethers were assigned to one of three treatments. Wethers received blue grama hay plus 1.6 mg swainsonine/kg BW (n = 5), 0.2 mg swainsonine/kg BW (n = 6), or no swainsonine (control; n=6). Swainsonine was administered by feeding locoweed (428 ug swainsonine/g dry matter). Blood was collected via jugular venipuncture at 12 h intervals on d 1, 8, 11, 14, and 18 to determine serum swainsonine, alkaline phosphatase, and aspartate-amino transferase activity. Rises (P < 0.05) in alkaline phosphatase and aspartate amino transferase activity indicated subclinical toxicity in treated wethers. Rumen samples were collected from 0 to 48 h in 8 h intervals to determine effects on ammonia and volatile fatty acid concentrations. Ammonia concentrations were lower (P < 0.05) for controls than treated animals at 8 h and higher (P < 0.05) at 24 and 48 h. Volatile fatty acid (VFA) concentrations essentially were not affected (P > 0.08) showing no time by treatment effect for all VFA except valerate. Valerate concentrations increased (P < 0.05) at h 8 in 1.6 mg swainsonine/kg BW wethers. In situ samples contained 5 g of treatment diets and placed into the rumen representing h 0, 3, 6, 9, 12, 24, and 48. Treatments were 0.2 mg swainsonine/kg BW (n = 4), 1.6 mg swainsonine/kg BW (subacute exposure; n = 4), 0 at 1.6 mg swainsonine/kg BW (acute exposure; n = 3), or no swainsonine (n = 3). Dry matter digestion was greatest (P < 0.05) for both the 1.6 mg swainsonine/kg BW and 0 at 1.6 mg swainsonine/kg BW treatments. Organic matter, NDF, ADF, and CP showed no effects (P > 0.1) on digestion. Duodenal and fecal flow rates were apparently unaffected (P > 0.09). Enzyme and swainsonine activity levels in serum indicated subclinical toxicity. However, lack of consistent results in digestive parameters indicates limited effects of swainsonine on digestive processes.

Last Modified: 08/18/2017
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