THE TOXICITY OF PYRROLIZIDINE ALKALOID-CONTAINING PLANTS AND OTHER HEPATOTOXIC AND NEUROTOXIC PLANTS
Location: Poisonous Plant Research
Title: A comparison of the metabolism of the abortifacient compounds from Ponderosa Pine needles in conditioned versus naive cattle
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 4, 2012
Publication Date: June 13, 2012
Citation: Welch, K.D., Gardner, D.R., Pfister, J.A., Panter, K.E., Zieglar, J., Hall, J. 2012. A comparison of the metabolism of the abortifacient compounds from Ponderosa Pine needles in conditioned versus naive cattle. Journal of Animal Science. Epub ahead of print.
Interpretive Summary: Ponderosa pine needles are known to induce abortion in cows when consumed during the last trimester of pregnancy. The toxin in the needles that induces abortions in cattle is the labdane resin acid isocupressic acid (ICA). Pine needles also contain lesser amounts of other related labdane acids (agathic acid, imbricatoloic acid and dihydroagathic acid), which may also be abortifacient. Even though ICA is the abortifacient compound in pine needles, studies have shown that ICA is rapidly metabolized in cattle. Previous research suggested that extended exposure of cattle to labdane acids resulted in altered metabolism and/or elimination of these compounds. The objective of this study was to determine if cattle conditioned to pine needles metabolize labdane resin acids differently than naïve cattle. The results presented in this study demonstrate that cattle conditioned to ponderosa pine needles can more efficiently metabolize the abortifacient compounds than naïve cattle. These results suggest that extended exposure of cattle to labdane acids results in a physiological change in the cattle such that the known abortifacient compounds in ponderosa pine needles are metabolized more quickly. The physiological adaptation appears to be an alteration in the ability of rumen microflora to metabolize agathic acid. Further research is necessary to determine if conditioning cattle to pine needles can be used as a potential management tool to prevent or reduce pine needle-induced abortions.
Isocupressic acid (ICA) is the abortifacient compound in ponderosa pine needles, which can cause late term abortions in cattle. However, cattle rapidly metabolize ICA to agathic acid and subsequent metabolites. When pine needles are dosed orally to cattle, no ICA is detected in their serum while agathic acid is readily detected. Recent research has demonstrated that agathic acid is also an abortifacient compound in cattle. The observation has been made that when cattle are dosed with labdane acids for an extended time, the concentration of agathic acid in serum increases for 1 to 2 d but then decreases to baseline after 5 to 6 d even though they are still being dosed twice daily. Therefore, in this study we investigated whether cattle conditioned to pine needles metabolize ICA, and its metabolites, faster than naïve cattle. Agathic acid was readily detected in the serum of naïve cattle fed ponderosa pine needles whereas very little agathic acid was detected in the serum of cattle conditioned to pine needles. We also compared the metabolism of ICA in vitro using rumen cultures from pine needle conditioned and naïve cattle. In the rumen cultures from conditioned cattle, agathic acid concentrations were dramatically lower than rumen cultures from naïve cattle. Thus, an adaptation occurs to cattle conditioned to pine needles such that the metabolism agathic acid by the rumen microflora is altered.