Irregular returns to estrus occur from 25 to 37 days post-service. A sow has an irregular return (abnormally long estrous cycle) when all the embryos have been lost (< 35 days of gestation) and are reabsorbed, or when only 5 or fewer embryos remain at 10 days of gestation.
Under normal conditions, these should account for a very small percentage of the matings < 3%.
![](https://www.pig333.com/3tres3_common/dist_nou/css/images/imb5.png)
Irregular returns are generally considered to be a problem when they account for more than 30% of the total returns, but it should be noted that when the total returns are very low, irregular returns will account for a higher percentage of the total, and this is considered normal, as the problem sows are those that return (we are not up against a problem).
Among the possible causes we must distinguish two major types:
Use the buttons above or the flowchart to continue troubleshooting the returns to estrus, or to 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/pig333/16361/irregular-returns_169588.jpg?w=820&q=1&ts=1653979446)