Based on reports from the European Union (EU) tracking horses sold to Mexico for slaughter and arial footage of a group of abandoned horses, EWA concluded that over 5,000 abandoned horses in the US can be traced back to meat slaughter plants in Mexico.
The EU report identified that over 5,000 horses sold to Mexico for slaughter were deemed, under slaughter regulations implemented in 2009, to be ineligible for slaughter. A similar number were found abandoned together in the same field. The large number of horses being found in one location suggested that these were not cases of owner abandonment; the proximity to Mexico suggests that these were the horses rejected for slaughter.
The link below begins a download of a PDF of the full press release from the investigation.