No, not several hundred for a day. If you are only gone a day, you'd be okay feeding them before you leave and when you get back. For example, if you can feed them on friday night and again on sunday morning, you are probably okay (athough I prefer to have someone stop by so I get them at least one feed every day) A 3-5 day vacation would require a couple hundred live shrimp (or a sitter), more days gone would require more shrimp but you would really be best off with a sitter when you're gone that long. The number of shrimp needed depends on the size of the shrimp and the size and appetite of your seahorses, but you have to remember that when you put in live food, they are going to pig out initially and eat a bunch, and you still have to have food left for the rest of the days, since a big meal the day you leave doesn't do them any more good than a normal sized meal, on average their digestive system will still start to shut down after 3-4 days without food, and they'll become more vulnerable to infection and disease after a day or two.
