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Mr Roberts (65), of Mosgiel, said he has been around New Zealand four times on his 32-year-old horse Zara and had never picked up her manure.
The idea to install a horse manure bin at Ocean View Recreation Reserve was ridiculous, he said.
When the Taieri Times visited the reserve earlier this month, dog walkers said it was unfair there were no consequences when horse owners failed to clean up manure from the reserve and beach.
Mr Roberts said dogs' faeces were different from horses'.
Dog faeces posed a health risk because they were made up of many unknown ingredients but a horse's was 99.9% grass.
Most young riders could not control a horse when collecting the manure and carrying a shovel and riding a horse was unpractical.
And ''if the horse has come off green grass it's shooting out liquid.''
Board chairman Scott Weatherall said the board was investigating ''achievable'' ways to deal with the manure.
Two ideas were a collection bin, or dumping it in a holding tank at the reserve for human waste from self-contained camper vans.
The logistics would be discussed with the pony club and the Dunedin City Council.