I pay a professional horsewoman $25 per day to come to my house and feed my indoor cats, barn cats, and horses twice a day. Her stable is ten minutes away from me.
This has been her fee, regardless of the number of horses I've had or the number of cats. She also will water plants, bring in the mail, and so on. She'll feed, water, check, medicate, and call vet for colic and deal with it, and so on.
When we started, I had 8 horses, with one requiring twice daily bandage changes and another three times daily eye drops. She did it all.
My horses are pastured, which may make a difference, but were all stalled and fed grain twice a day except summer. Stall cleaning not included. Litter box cleaning included.
I have fewer horses now, but more cats (not by choice), but I pay the same amount. In summer, I only ask her to come once a day because they only need a look-at and watering, but I figure the trip and the responsibility are what I'm paying for.
Different areas will have different prices, and it no doubt also depends on who you know and how hard you are to work for.