How long is estrus in rats? - briefly
In female rats, the estrus phase lasts approximately 12–14 hours, occurring once within a 4–5‑day estrous cycle.
How long is estrus in rats? - in detail
Estrous cycles in laboratory rats last 4–5 days, with the estrus phase comprising roughly 24 hours. The cycle proceeds through proestrus (≈12–18 h), estrus (≈24 h), metestrus (≈12–18 h), and diestrus (≈48–72 h). Vaginal cytology identifies the estrus stage by a predominance of cornified epithelial cells; behavioral observation notes increased lordosis and receptivity to males.
Several factors modify the length of the fertile window:
- Strain: Sprague‑Dawley and Wistar rats typically display a 24‑hour estrus, while some outbred stocks may extend to 30–36 hours.
- Age: Young adults (8–12 weeks) maintain the standard duration; older females often exhibit prolonged diestrus, shortening the overall cycle.
- Photoperiod: Continuous lighting or abrupt changes in light‑dark cycles can shift the timing of proestrus onset, indirectly affecting estrus length.
- Hormonal manipulation: Exogenous gonadotropins or antagonists can lengthen or truncate the estrus phase, depending on dosage and timing.
Monitoring protocols usually involve daily vaginal smears taken at the same circadian time to reduce variability. A typical schedule records cornified cell dominance for 1–2 consecutive days, confirming the estrus window for breeding or experimental interventions.