Setting aside the general etiquette of picking up (or not) after horses (Letters, 19 January), there is in fact decent evidence that dog poo poses rather more of a public health risk than horse muck – in terms of pathogens, parasites, diet, and how long the stuff remains infectious.

This is not a new debate. As a sergeant in the mounted department in the 1990s, I once found myself dispatched to Radio Merseyside’s Roger Phillips phone‑in to defend our position during an entire programme devoted to complaints about police horses leaving their calling cards in the city centre.

I learned more about equine zoonoses while preparing for that broadcast than I have ever needed since – though colleagues were entirely unsurprised to hear that I’d managed to spend an hour on air talking shit.
Terry O’Hara
Maghull, Merseyside

Reading the letters regarding horse manure, I was reminded of my father in the 1960s when we went for a run out on a Sunday in our little Vauxhall Viva. Spotting a pile of horse manure, he would give a joyous shout of “Road apples!”, pull to a halt and jump out to gather the treasure. He kept a small shovel and a sack in the boot for precisely such occasions. His garden was grateful for the bounty, and I have always remembered the pleasant smell of horse dung as a consequence.
Kay Burkinshaw
Stannington, Sheffield

Having had dogs and ponies to pick up after, I would suggest that dog poo is a more toxic and smelly substance that legally requires removal from public places, while horse poo is basically vegetable matter and friendly bacteria, and goes beautifully on compost heaps. It biodegrades quickly too.
Alex Gallagher
Cranbrook, Kent