Across the world, zoos have tried such delicacies as : raw egg, porridge, boiled cockroaches, and apples. And at least two zoos (Oklahoma City Zoo and Basle Zoo) have tried horsemeat. Thus it seems almost certain  that, along with some humans, various pangolins have also been exposed to Involuntary Hippophagia (the unintended ingestion of a horse, or part thereof).
Source, see: ‘History and dietary husbandry of pangolins in captivity’ (Zoo Biology, Volume 26, Issue 3, pages 223–230, May/June 2007)
 Improbable is confident that pangolins are extremely unlikely to have eaten horse in the wild – thus the hippophagia is involuntary.
 Improbable also has reason to believe that captive Aardvarks too have been subjected to Involuntary Hippophagia. “The meat portion of the mixture may be ground, chopped or mixed horsemeat, dry dog food or processed feline food (eg Nebraska Brand Feline Food is used at Pittsburgh, Zu/Preem Feline Diet at San Antonio) “ See: ‘A review of the management of the Aardvark: in captivity’, Corey A. Goldman, International Zoo Yearbook, Special Issue: Including volume 25 Volume 24, Issue 1, pages 286–294, January 1986.
 The photo shows a Chinese Pangolin at Leipzig Zoo snacking on something that may or may not contain some/none of the ingredients listed above. (courtesy: Nachbarnebenan at Wikipedia)