First things first - sale of an wasting asset is not liable to CGT. You're not in a trade of selling ponies so no charge to income tax.
Which brings me to my next point, its a pity you don't have such a trade as you could have written the loss on the pony against other profits or income you have from elsewhere !
(Before you ask - you don't and can't have a trade with just one pony)
anybody with more than one has my deepest sympathy!
daughters or ponies!!!!!!!