New Zealand Anti-Vivisection Society executive director Tara Jackson, of Christchurch, said the protest, at 11.30am on Saturday, showed "how strongly people feel about" the issue, given wet conditions on the day.
And Ms Jackson felt "pretty good, pretty inspired" by the level of participation in the 90-minute protest outside the Hercus building.
Protesters objected to what they said was needless suffering experienced by laboratory animals, including those used in current experiments at the university.
Ms Jackson said human cell lines could be cultured outside the body, including in petri dishes, and in some cases some human body structures could also be developed outside the body. Her organisation believed that using such human resources for research was more morally and scientifically responsible than undertaking animal experiments.
An Otago University spokesman said the university "recognises that there are different views on this matter, but believes that animal-based research is a vital component for important medical and scientific advances".
Claims of animal mistreatment at Otago University were "outrageous and unfounded", the spokesman said.
"All animal-based research undertaken at Otago goes through a strict ethics approval process and is carried out as humanely as possible.
"The care and treatment of animals housed in our facilities is of the highest standards and is undertaken by professional staff who take their animal welfare responsibilities very seriously.
"Animals are only used in research or teaching if there are no appropriate alternatives. Cell lines, human-based research or computer simulations are used extensively in place of animal research at the university where possible," he said.