Horniman has thirty years' experience in the veterinary industry and spent more than twenty of those running a group of private veterinary practices which he has since sold.
His appointment fits in nicely with Sativa’s move into the veterinary market, which it announced last month.
As part of his new senior management role, Horniman’s job will be to explore the use of cannabis-based treatments in animals.
He will also be tasked with liaising with the relevant agencies to establish CBD regulation and progress Sativa's medicinal cannabis Growing Licence application.
“As announced in [January], Sativa is planning to enter the potentially lucrative CBD veterinary market through Sativa Veterinary services,” said Sativa chief executive Geremy Thomas.
“The CBD veterinary market has already taken off in North America and Dr Horniman will also advise on how best to go about launching the veterinary arm in the UK.
Horniman has been granted options over 3.1mln shares in the company with an exercise of 6.5p per share.
Sativa shares closed at 5.25p on Friday afternoon.