GLAD Scale for Ranking Welfare of Horses on Arrival after Transport to Slaughterhouses.

To date, there is no official method for measuring horse welfare after transport. This study aimed to develop a scale to classify horses into four categories: good shape; light affected; affected; down (GLAD) based on their welfare impairment measured at unloading. To this end, 15 animal-based measures (ABMs), previously recorded from 1019 horses, were scored. Weight and severity scores provided by welfare experts, alongside the number of welfare principles highlighted by the ABM, were assigned to each ABM. The welfare impairment () of each horse was then calculated as the weighted sum of the severity scores of the 15 ABMs. Three thresholds were also set to define the four GLAD categories; the ABM "down" (i.e., horses unable to stand and walk on arrival, also considered by the law as the indicator of the worst welfare) was used as the higher threshold, , (category D); the intermediate threshold, , was defined by the ABM "injuries", assumed to represent highly impaired welfare (category A); the threshold, , was defined assuming that significant welfare impairment starts from 20% of (L category). Horses with an value below were considered physically and mentally fit (G category). Out of 1019, 43% of horses fell into category G, 48% into L, 9% into A, and 0.3% into D. Our scale could be useful for veterinarians to decide whether a horse can be slaughtered immediately (G), needs rest (L), needs attention (A), or euthanasia (D), but further validation is needed.