The standard CEL policy does not cover these situations, but you may add CCC coverage to your policy or obtain CCC coverage by itself. Actually you still need this coverage. If one of those horses dies and the insurance company pays the claim but they believe you or your employee were negligent in causing the horse's death, you can still be sued by the horse owner or their insurance company. If this happens, the CCC policy will pay for your defense and pay claims up to the coverage limits. I occasionally trailer boarded horses to shows for their owners.
Policies are available in all U.S. states except Alaska, Hawaii, and Oklahoma.