Exact, 1500 is not a such big amount as people thinks. If we use correctly the term animals, expanding it to flies, worms and zebra fishes instead to use it incorrectly as a synonym for "birds and mammals", the real number should be much higher.

To kill 1500 vinegar flies in a week for research is not uncommon or a strange thing.

We need to remind that the faster you do research, the more people will be saved by research. The problem here is not the amount of lab animals killed.