I agree with the others, I don't believe the smell of horses or cattle spook deer.
There's been a few times I've rode fairly close to deer but it was because the wind was blowing hard enough that they did not here me coming toward them.
The deer do pause and watch for a moment but once they see you moving toward them they perceive that to be a threat and take off running as most prey animals will do.
I have had deer come in my dry lot and lick the mineral block with the horses standing close by in the lot.
Also had a doe in my round pen once, don't know what her plans were.
As for covering your scent one of the best things I've found is cedar trees.
I've built ground blinds using cedar branches and also have cut me a depression back in a cedar tree, if you sit still you will be amazed at how close the deer will come to you.
My brother done this one time and set in one of them fold out chairs, the kind you set down in.
It was colder then heck that morning, he got all comfy setting in the chair, the cedar tree blocking the wind and he fell asleep.
Well he got to snoring and believe me he can snore.
He snored so loud he woke himself up and when he opened his eyes he sees an 8 point buck standing there looking at him not 20 yards from him.
So he sits still until the deer decides to turn and walk away from him and when he felt the time was right he raises his rifle and fills his tag.
I bet that deer never heard a cedar tree snore before.