WARNING: This story contains upsetting images.
As El Rocio comes to an end, animal rights organizations have called on authorities to do more to protect the animals used in the annual celebrations.
A shocking video and photographs taken during the week long Romeria festivities reveal the extent of equine collateral damage associated with the event.
Each year, the Monday before Pentecost more than a million people are drawn to the hamlet of Rocio, near Alamonte, to pay homage to the Virgen of El Rocio, with six days of dancing, drinking and partying.
The crowds come on foot, on horseback or in horse drawn carriages and each year and as a result the event is tainted by reports of animal cruelty.
In the last seven years at least 107 horses have died during the annual events.
Spain's animal rights charity Partido Animalista PACMA on Thursday released disturbing footage showing the poor condition of some animals and the deaths of several horses during this year's fiesta, including a pregnant mare and her unborn foal.
"Each year donkeys, horses, mules are abandoned along the pilgrimage route because they have collapsed from heat, exhaustion, a lack of water. Others die from untreated colic," Silvia Barquero, the president of PACMA told The Local.
The charity attended El Rocio to document examples of abuse. As well as recording numerous examples of animals suffering malnutrition they also documented animals with open sores and carrying loads beyond their strength.
"During El Rocio, some people treat their animals like they are motorbikes. But they need great care. They may be very powerful animals but they need to be treated properly or they will suffer and die," said the charity chief.
The worst images show horses that have died along the 60km pilgrimage route, including one horse being scooped in a municipal tractor's shovel and dumped into a container of other dead animals.
VIDEO CONTAINS UPSETTING IMAGES
"We don't have the exact figures yet on how many animal deaths occurred during this year's Rocio but between 2007 and 2014 at least 107 horses have perished,” Barquero explained.
"One of those seen dead in the video is a mare who has given birth prematurely to her foal. Using an animal that is pregnant is against the law yet it happens and there are rarely prosecutions," arquero complained.
The charity along with other animal rights organisations are campaigning for an outright ban on animals being used in the Romeria.
"There are regulations already in place to protect animals, but they do not go far enough and the crimes are not investigated,"she said.
"Those animals dumped in a container all have chips and their owners could be traced and prosecuted for animal cruelty but there is little desire by authorities to pursue it," she added.