ABSOLUTELY. One of the worst things we can do is not treat an infection long enough. The animal may appear better, but that is because the infection is under control, not necessarily gone. If we stop the antibiotics
too soon, the infection could recur and even worsen.
By not giving the full course of antibiotics, we may also inadvertently, help the growth of bacteria which have developed a resistance to the antibiotic. By 'resistance,' we mean some bacteria may have mutated or changed, so they are not affected by an antibiotic that previously killed them or slowed their growth. As more bacteria become resistant to various antibiotics, there are fewer antibiotics which will have an effect on them, thus newer and stronger antibiotics will need to be developed. Inappropriate use of antibiotics (using them too often, for too short a duration or in insufficient doses) may promote the development of resistance.