Buyers want larger size animals to obtain the maximum meat yield, so go for thoroughbreds and riding horses, the study indicates.
The researchers looked at the animals put up for sale at seven randomly selected auction markets in Britain in August and September 2011, and the type preferred by dealers buying on behalf of abattoirs.
The auctions were in North Yorkshire, West Yorkshire, Wales (Powys), Berkshire and Cheshire and traded equines only, but of all types, breed and age.
Their study was prompted by public concerns about the possible dispatch to slaughter of pet horses and donkeys and unwanted thoroughbred racehorses.
The authors examined 384 animals, which included a broad range of cross breeds, thoroughbreds, and ponies, and found out the destination of the 294 that were sold. Ninety were either withdrawn from sale or didn't reach their reserve price.
Just 68 were bought on behalf of the three main horse abattoirs operating in Britain in 2011, while 226 were bought by other types of buyer.
Almost half of the horses and ponies put up for sale were geldings (42%), followed by mares (30%), fillies (16%), colts (10%), and stallions (2%). Height varied from 9 to 17 hands while age ranged from under 12 months to 21 years.
Animals destined for the meat trade were around 2.5 times as likely to be larger - taller than 15 hands - than those bought by other outlets. Horsemeat buyers avoided ponies and cross breeds and instead opted for thoroughbreds and riding horses (43%). The price per hand for meat trade animals varied from £1.31 to £57.79.
Dealers buying on behalf of abattoirs were twice as likely to purchase animals that had some physical abnormality, including flesh wounds, burn injuries, bruises, swellings, bleeding, discharge, hair loss, or deformity, as those buying for other outlets (26% compared with 13%). And 16% of the animals destined for an abattoir were lame.
The authors conclude: "Equine buyers supplying horse abattoirs in Great Britain had a preference for purchasing larger animals and they avoided buying ponies. This is thought to reflect a preference for animals which provide a maximum meat yield from the carcase to cover the cost of transport, slaughter, and dressing."
They add: "A relatively small proportion of unwanted ponies and small horses were destined for the meat trade. In general, the findings from this study did not support the view that the abattoir industry focused on profiting from the slaughter of pet ponies."