Yes, moral grounds, I'm sure. But there are all sorts of abhorrent treatment of animals - abattoirs, indoor farming, force feeding, etc, etc - so, why is it a moral line to drown rats in the way described? Who decides this stuff?
The ethical committee of whatever university or research organisation is responsible for the person who wants to conduct this experiment.
Also, many countries have laws on animal wellbeing that may supersede even a green light from the ethical committee.
You can do a scientific study without torturing the animal - if you have snow alternative, please explain clearly why, why you study is important enough, and convince the ethics board.
You can eat all kinds of things without torturing the animals - if you have no alternative please explain clearly why, why eating meat is important enough, and convince - actually absolutely nobody, nobody in power cares about animal suffering in our food system.
And before you ask, no not everyone has to eat meat, but, there is at least the reason that an all plant diet is intractable to some people for the sheer amount of carbohydrates, and for others due to the mental load of making sure they get the nutrients that are hard to get in plants but easy to get in meat.
But it's probably also more convenient to do drowned rat studies to figure out specific things than it is to construct more elaborate ones to ascertain the same kinds of findings. So I don't think my take is that far off the mark, still.
This isn't true,as proven by the many laws and regulations about it for decades.
https://en.wikipedia.org/wiki/Timeline_of_animal_welfare_and...
Just because abhorrent treatment of animals exists in one industry doesn't mean it's OK for it to appear in another, or in this case, in the field of science.
As you can imagine, there isn't a single combined committee for these two...
That is why Tyson et al don't have an IRB.