Regular returns to estrus occur 18 - 24 days and 38 - 44 days post-service. A sow has a regular return (maintaining the normal duration of an estrous cycle: 18-24 days or its multiples) when fertilization of the eggs has failed or when all fertilized embryos have been lost within the first half of the estrous cycle (<10-12 days).
Under normal conditions these should make up a very small percentage of the matings, < 5%.
![](https://www.pig333.com/3tres3_common/dist_nou/css/images/imb5.png)
Among the possible causes we must distinguish between two major types:
Causes related to the semen dose (or boar)
Use the buttons above or the flowchart to continue troubleshooting the returns to estrus, or access other parts of the tool.
![Types of gestation losses that can lower the farrowing rate, detailing the different types of returns to estrus based on they occur.](https://www.pig333.com/3tres3_common/art/pig333/16360/regular-returns_169587.jpg?w=820&q=1&ts=1653979446)