Hi, You have a lot of good questions. How old are you? there is quite a difference between the Bovine, and Porcine and Equine, I dont know much about the horse it is pretty new a few people here have them.
First for the most part, the pig valves are actual pig valves, treated to make them less likely to calcif as quickly, but there are a few Porcine Valves being used today, some have better track records Of the ones commonly used today, the Hancock II probably has the longest track record, its been in use over 20-25 years (sorry Im in a hurry so cant look up links) and in people 60 and up who are still alive 20 years the majority of people still have it and it is doing fine. IMO it seems The Hancock II isnt used much in the US, I know some centers in Canada prefer it. Other porcine valves are the freestyle and medtronics Mosaic, the Mosaic was supposed to be the" new improved" Hancock based on the Hancock, but at least from here, it isnt one I would get or advise a loved on too IF you search here for hancock II Norm has alot of good info o it.
there are also a few Bovine, but the most part instead of being made of a cows valve, it is actually made from a cows pericardial sack, that is treated a couple ways to make it strong and plyable and also "thermafix" is supposed to get rid of the parts calcium binds too, to hopefully keep them from calcifying as quickly untreated tissue. CE makes the most pericardial valves the Perimount , is a 2nd generation pericardial valve and has been used in Patients since the early 80's for trials and 90 FDA approved, there are several kinds models of perimounts.
http://www.edwards.com/Products/HeartValves/Pages/PericardialCategory.aspx But for the most part, for a person 60+ there is a good track record of like 85% still doing well hemodynamically at 18+ years.
SJ Jude has a tissue valve, the biocore I believe it is mixed pig /cow, it has only been in use in the US a short time, but have 20 year records in Europe with good results last I looked..
One other thing that could make a difference w/ the various tissue valve someone gets today, Some valves have wider openings than other types of tissue valve, and other features that would make getting a tissue valve placed inside it in the cath lab IF /when the tissue valve needs replaced. They already have an idea of some tissue valves are easier to get a valve inside than others. I know the Perimount is one of the easier to get a TAVI inside, because it has a large opening relative to the size a person gets and it has a good "landing zone" for the doctors to place the new valve on.