Genetically Modified Virus To Kill Bacteria

I heard recently that there is a genetically modified virus that is used in the production of livestock.   This virus is made to kill bacteria and thus allow cattle producers to avoid using antibiotics in their livestock feed.  At first glance, some may think this is a good idea as it eliminates the use of antibiotics in meat production.   But what about raising the cattle in such a way that they are not sick in the first place and in need of anything to keep them from dying before they can be killed for market?  I must be a Luddite or something, but I don’t like this scary idea.  I did a Google search and I can’t find any specific information on this, so I am not even sure it is really true.  Anyone heard of it?

I did come across a reference to scientists developing a genetically modified virus that controls mouse populations by making the females sterile.  Now that is a great idea.  Release something like this that is supposedly tested to be mouse specific and then find out that, whoops it does indeed cross over to a different species.  Even if it is mouse specific, what happens to all the animals that eat mice as part of their diet once all the mice are gone?

I really am concerned about the idea of using genetically modified viruses and bacteria for anything at all.  It just seems like one mistake may be one too many and we all know a mistake wiould probably be inevitable.