I know that mice are disqualified if they don't interact for at least 30 seconds during the test. I am wondering if there is literature on rats and what is considered too little interaction?
I have no experience of laboratory test, however free ranging animals actively avoid interactions, and I believe this avoidance should be considered in studying the social relationships among them. Given your study topic, I advise to take in account the timing of interactions, instead of discarding the short ones.
Yes, Dr Md. Moniruzzaman is absolutely right . Among them, the sex of animals, the size of camera, cage or open field have the influence upon the time (latent period, in sec) before the interaction between the animals will be started. The mean value for rats and mice, I believe, about 20 - 30 seconds. It is suggested that animals are healthy.