What to Do If a Sow Returns to Estrus? Detailed Explanation of Handling Methods
First find the reasons why the sow returns to estrus, and only then can you find the handling methods. Generally speaking, the reasons for a sow returning to estrus include improper breeding timing, poor semen quality of the boar, failed mating by the boar, neglect of breeding hygiene, delayed ovulation or failure to ovulate in the sow, sow metritis, excessively high temperature or fever in the sow, management-related stress, hereditary reasons, and so on. Different reasons for returning to estrus require different handling methods.
1. Improper breeding timing
The best timing for breeding a sow should be 6 to 18 hours before ovulation; breeding too early or too late will not work. If the sow returns to estrus within 20 days after breeding (18-19 days), it means breeding was too late; if it returns to estrus after 22 days (23-24 days), it means breeding was too early. In the future, improve estrus detection and grasp the best timing for insemination.
2. Poor semen quality of the boar
Semen quality is one of the main factors affecting the conception rate. If the boar's semen quality is poor, breeding will fail and the sow will return to estrus. Before each breeding, the semen quality needs to be checked to ensure the semen quality is qualified.
3. Failed mating by the boar
Some boars may suffer from reproductive system diseases, and even if mating behavior occurs, they may not ejaculate. Since there is no ejaculation, the sow's breeding fails and it returns to estrus. It is necessary to select boars that are healthy and free of disease, with testicles of the same size, arranged symmetrically, and obvious male characteristics.
4. Neglect of breeding hygiene
If hygiene is neglected when breeding a sow, it may cause uterine inflammation in the sow. For example, touching the front end of the insemination tube and the foam head with the hands may contaminate the insemination tube; or the vulva of a sow in estrus contacting sewage may cause the sewage to be absorbed into the uterus through the capillary action of the vaginal wall. During breeding, the sow's vulva should be cleaned, and can be thoroughly wiped clean with disinfectant wipes.
5. Delayed ovulation or failure to ovulate in the sow
If the sow's ovulation is delayed, it will cause the inseminated sperm to lose their fertilization ability; if there is no ovulation, the sow will be unable to conceive. It is recommended to add 1% Shengming No. 1 for 7 days before breeding and 10 days after breeding to promote estrus in the sow and improve the ovulation rate and conception rate.
6. Sow metritis
Sow metritis is the main cause of sow infertility; it hinders the movement and survival of sperm, thereby hindering fertilization. Preventive health care for sows should be done well, routine epidemic prevention should be done well, and cleaning and disinfection should be done well during artificial insemination to prevent uterine inflammation. If sow metritis is found, it should be treated promptly.
7. Excessively high temperature or fever in the sow
From 14 to 25 days after breeding is the embryo implantation period. If the sow suffers heat stress or fever within 14 days, it will change the composition of the uterine milk, causing pre-implantation embryo death and leading to the sow returning to estrus. If heat stress or fever occurs from 12 to 24 days or even up to 35 days, it will affect embryo implantation or cause the death of embryos that have already implanted, thereby causing the sow to return to estrus. Preventive health care for sows should be done well, and a comfortable living environment should also be created for the sow.
8. Management-related stress
If stress such as fighting, pen transfer, or transport occurs, it will cause excessive secretion of adrenaline in the sow, affect the composition of the uterine milk, and thus lead to embryo death. Therefore, the management of sows should be done well, and behaviors or actions such as fighting, pen transfer, and transport should be avoided.
9. Hereditary reasons
If the embryo develops poorly and cannot implant normally, it will cause the sow's breeding to fail and cause the sow to return to estrus. It is necessary to grasp the best insemination timing so that sperm and eggs combine at the best time, and do not cause forced fertilization because the best combination time is missed.