Did they eat all the vegetation (grass) in the old pen where these bushes are? What kind of shrubs, how big? Plants that have an excess nitrogen load will often resemble plants that are UNDER fertilized. I'd be a bit concerned, but not knowing your soil or climate, all I can do is sit here and speculate about what your climate is like now, and what your soil parameters are now. If these shrubs are important to you... if you want to be sure they don't die, it might be worth having the soil tested. I think the basic NPK test is about $15, and you can buy a kit for multiple tests for around $22. If you are not too specific about the outcome, you could give them a dose of liquid fertilizer and see what happens. Have they leafed out yet, or are they still dormant? If they've leafed out, what do the leaves look like? Can you post a picture? I wouldn't fertilize any shrubbery until it's broken dormancy.