Staging of Estrous Cycle in Rats using Vaginal Cytology and Visual Assessment

The determination of different phases of estrous cycle in lab animals is important for reproductive interventions and other experiments related to animal reproduction where rats are used as experimental models. A total 21 Wistar albino (which had completed their pubertal stage ( greater than 4 weeks) weighing approximately 100- 200 g were used in this experiment. Visual assessment was done to observe vaginal opening during different phases of the estrous cycle. This was followed by collection of vaginal discharge samples by flushing it with 0.1 ml of distilled water using micropipette. Vaginal cytology was performed in 21 rats thrice daily, along with visual assessment. The average length of estrous cycle in rats was recorded to be 4-5 days with average duration of proestrus, estrus, metestrus and diestrus of 24, 24-36, 12 and 48 hours, respectively. The average length of estrous cycle in rats was 4-5 days with recorded average duration of proestrus, estrus, metestrus and diestrus of 24, 24-36, 12 and 48 hours, respectively. Vaginal cytology can be considered as a better option compared to visual assessment for assessment of reproductive status in rats.