there are a few ways you can look at him and tell that he cant breed, such as an injury and something abnormal. but the only sure way that i know of to know if he can breed or not is to have a vet to semen check him.
Most salebarns will check a bull if you buy one there. The local barn here charges $35. Probably similiar price if you take in a bull you bought else where to your local vet. Not sure what the electro-stimulation procedure runs, probablya little a bit more. Unless you know the owner/seller personally and have seen calves from particular bull, you really should get him tested. No reason to waste 3-4 months just to save $35.
While this will tell you his fertility level, it wont tell you anything about his libido. Therefore the pen full of cows would come in handy.
Thanks again everyone for replies I noticed the bull does not pay much attention to the cows ,they fight with him alot but he is new to them.I did not see him mount any cows yet he does smell the cows some not that much let you know if I see any action thanks again Dean
wait til you know one is in heat, you should be able to see him breed if you watch long enough. but some only breed at night . whether you see him breed them or not mark down date & see if they come in heat in about three weeks.
You need to be sure he is fertile. You can't tell by just looking. Did he have a BSE? But there's not a test to check his willingness to breed. So you need to watch him. Make note of when the cattle are cycling and if he breeds them, watch them again at about 18-22 days to see if they return to heat. We use a chinball marker on our gomer bull. When he mounts a cow, he leaves a streak of yellow paint on the cows and we know they've been standing, plus we know he's done his job. Good luck....