It's interesting that you mention jersey's. I had a fine old friend who was quite cow savvy who loved jerseys. He figured about 3/8 jersey was about right in mother cow.
After 1st calf, he'd put charolais bulls on them. According to him, they were the only high milking cow developed to milk off of grass alone. Had a tremendous pelvic size, in comparsion to their own size. Internalized their fat, like deer--this went somewhat to marbling, tenderness. And extremely fertile.
He had a set of them out on shares==partially calved out and he hadn't kept tabs on them. Many of these cows were in bcs of about a 2. Horrible deal---almost starved to death. I took them on shares, as he had no place to go. They calved out, weaned decent calves, put on some weight and bred back.
I'm pretty casual about taking my bulls out---figure a late cow, you got options, an open one you don't. But with these--you gotta or lutelyce hiefer calves---
A pretty good sized outfit north of here runs straight herefords, must pretty much let them calve on thier own. Uses 3/4 or full jerseys on their heifers. My buddy bought the heifer calves off the heifers--100+ of them. I helped preg them---wildest little bunch of sumbitchs you ever saw---when you moved them from big pen to smaller one going to alley, they'd flow up the side of pen---like quickly dumping water from one bowl into another. One of them little darlings ran by me at mach 1, about 4 feet away, sunfished and kicked me in the knee cap with both hind feet. As vet said, as I got back to my feet from kick and he got straightened up from laughing himself sick---"quite athletic little devils, aint they?"
My old buddy put togethor a presentation/show me deal on his program. He had a couple college professors from ohio, an economic developement guy and an extension type, also from ohio and a local charolais breeder. We looked at the cattle, then he had an indoor presentation---and the college professors was taking notes. Priceless.
I asked them what their angle was. They said they had hundreds of thousands of acres of reclaimed coal ground, could probably graze 10 1/2 mos of the yr, and multiple generations of people on welfare. Figured a smaller framed cow, with potential to produce big beef calves and good disposition might be a good fit.
These were nice cattle to work---with one exception, and I put that down to envirionment.