Sublethal levels of toxic larkspur: effects on intake and rumen dynamics in cattle
Pfister, J.A. | Adams, D.C. | Arambel, M.J. | Olsen, J.D. | James, L.F.
Four ruminally-cannulated steers with an average body weight of 260 kg were fed an alfalfa hay basal diet and dosed intraruminally with 0, 150, 300, 450 g/day of ground larkspur (Delphinium barbeyi) in a Latin-square design. Larkspur contains diterpenoid alkaloids and when consumed at levels near 2.5 g/kg body weight, is a highly toxic range plant. Doses were designed to imitate sublethal ingestion of larkspur by grazing cattle. Larkspur had no influence (P greater than 0.1) on crude protein or fiber digestibility, ruminal fluid volume, fluid turnover time or fluid dilution rate. There was a positive quadratic effect with the addition of the lowest level of larkspur for dry matter intake (P = 0.08), digestible dry matter intake (P = 0.01), dry matter and organic matter digestibility (P = 0.06), and ruminal fluid flow rate (P = 0.09). Ruminal ammonia-N levels showed a negative quadratic response (P = 0.03) to the addition of the lowest level of larkspur. Total viable bacteria numbers tended (P = 0.4) to decrease with increasing amounts of larkspur. Larkspur is apparently a nutritious range plant when consumed by grazing cattle at levels that do not produce visible symptoms of intoxication, as indicated by muscular tremors, sternal recumbancy and respiratory paralysis.
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