Warwickshire's County Record Office feature a Record of the Month on their website: August's was Sir Richard Newdigate's Horse Book. Sir Richard Newdigate (1602-1678) lived near Nuneaton, and was Lord Chief Justice during the Commonwealth. He was something of a micro-manager, leading to a very fast turnover amongst his household staff: his stables were closely supervised too. Did this, I wonder, lead to a fast turnover amongst the stable staff?
His horses were a source of family friction: his family thought he spent far too much on his horses, and in his comment on the document (though alas you cannot see this - you can't enlarge the view) he remarks that other breeders with far worse horses ask higher prices. He values his at at much as 50 -60 guineas each, a substantial sum then. I presume that the horses had not been selling as he was over-pricing them. Perhaps Sir Richard was not eager to sell: he remarks later in the document that breeding the horses saved having to buy them. True, though his family had obviously spotted that breeding them on the scale Sir Richard did was not actually saving money; particularly when you didn't sell them.
Many thanks to Rosemary Hall for telling me about this.