Effect of previous locoweed (Astragalus and Oxytropis species) intoxication on conditioned taste aversions in horses and sheep.

The study examines how the ingestion of a toxic plant called locoweed (Astragalus and Oxytropis species) impacts the ability of horses and sheep to develop taste aversion. The findings suggest that animals previously intoxicated by locoweeds can form strong aversions to new feeds, although the strength of aversion may not be as strong as in animals that were never intoxicated.

Research Objective and Methodology

The primary objective of this research was to understand if prior locoweed poisoning affects the ability to learn food aversion in horses and sheep.

• Three groups were created for both sheep and horses: control, locoweed-novel feed averted, and averted.
• The locoweed-novel feed averted groups were fed locoweed for two periods of 21 and 14 days respectively, with a14-day recovery period following each feeding phase.
• A new test feed was introduced at the end of the first locoweed-feeding period, and animals were evaluated periodically for the persistence and strength of the aversion.

Study Findings

The study findings were focused on the responses of the animals to the test feed following exposure to locoweed.

• During the first recovery phase, locoweed-novel feed averted horses ate significantly less test feed compared to control horses and did not generally differ from averted horses.
• In the second recovery period, locoweed-novel feed averted horses significantly differed in consumption of the test feed from controls and the averted group.
• Locoweed-novel feed averted sheep differed from controls, whereas locoweed-novel feed averted sheep did not differ from averted sheep. During the second recovery period, control sheep significantly differed from averted and locoweed-novel feed averted groups.
• Two intoxicated sheep partially lost the aversion during the first recovery period, but an additional dose of LiCl restored the aversion. Two of the three intoxicated horses had strong aversions that remained, while one horse in the locoweed-novel feed averted group had a weaker aversion.

Conclusion

The study concludes that horses and sheep that have previously been intoxicated by locoweed can form strong and lasting aversions to a new feed. However, in some animals, these aversions may not be as robust as those in animals that were never intoxicated. This information could be valuable in managing livestock’s grazing behavior and health outcomes.