I came across this forum while looking for new things to teach my cattle and noticed that there were a couple of threads with people training cows that hadn't been able to find much information on the subjectand hadn't progressed very far. As a prolific cattle trainer, I had to come on to share the goods and fly the flag for cattle!
What you want to look for is information about oxen - cattle have been domesticated and in use for work longer than horses have. An ox is merely a bovine with an education, and there is plenty of material out there about using them for draught which gives you a start, even if it is quite 'narrow'. Stuff about riding, let alone 'natural dressage' is rare, but rest assured, cattle can do most of it too, with a few concessions due to physical limitations e.g: you won't get the 'outline' you get with a horse, given the shortness of the neck, they have less spring/bounce in the leg(but are very agile and flexible, just check out the moves on PBR if you need proof!) and they would find it difficult to rear as that's not really something they do in general.
They are extremely quick to learn and never forget a lesson, which can go both ways! They also hate repetition and micromanagement in my experience, and respond by slowing down and becoming stubborn. Material about training donkeys I have found very useful as the mindset is very similar. They are very spook-proof as they would rather face a threat than run from it and let very little bother them.
Mine do a little of everything - tricks, pulling loads, longreining/driving, riding and just being great pals
I ride treeless, bitless, barefoot and stirrupless and have experienced absolutely no problems training them to respond this way. 
I guess you have seen the posts by Elke (bloem) here in the forum, who is also playing with her cows. 
So great! I love the jumping picture! 
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