The Hormones of Farrowing: What Pork Producers Need to Know, Todd Thurman, Swine Insights International

As pork producers, we’re always looking for ways to improve our operations. While we often focus on practical application of nutrition, genetics, health and management practices, there are underlying biological processes that play crucial roles in successful production. One of the most important is endocrinology. Understanding the hormonal changes that occur during different stages of production can help us make better management decisions and potentially improve piglet survival rates, sow longevity and overall productivity. While endocrinology is most often discussed in the context of breeding and heat detection, this post will focus on the endocrinology of farrowing.

Note: The following explanation is simplified. A complete treatment of the endocrinology of farrowing is far beyond the scope of this post. The goal here is to provide a useful overview for producers and managers. Extensive resources are available for those interested in developing a deeper understanding of these functions.  

The Hormonal Shift From Pregnancy to Farrowing

Throughout pregnancy, progesterone is the dominant hormone. Often called the “pregnancy maintenance” hormone, progesterone keeps the sow pregnant by preventing uterine contractions and maintaining the uterine lining. However, as farrowing approaches, a dramatic shift occurs.

A few days before farrowing, progesterone levels begin to drop sharply. This is the result of a cascade of hormonal changes initiated by the piglets themselves that will ultimately result in the birth of piglets. The piglets release corticosteroids which act on the sow’s placenta to release prostaglandins which cause the sow’s ovaries to reduce progesterone levels. As progesterone decreases, other hormones start to increase, most notably oxytocin, relaxin and prolactin.

Oxytocin: Nature’s Labor Inducer

Oxytocin is often referred to as the “birth hormone.” As progesterone levels fall, oxytocin levels begin to rise. This hormone has two primary functions during farrowing:

1. It stimulates uterine contractions, helping to push the piglets out.
2. It triggers milk let-down, ensuring colostrum is available as soon as the piglets are born.

Interestingly, oxytocin release is influenced by environmental factors. Stress can inhibit oxytocin release, which is why it’s crucial to provide a calm and comfortable farrowing environment.

Relaxin and Prolactin: The Supporting Cast

While oxytocin is the star of the show, relaxin and prolactin play a vital supporting role by:

• Relaxing the muscles around the birth canal.
• Softening the cervix.
• Supporting mammary gland development and maintenance.

The Colostrum Connection

As we discussed in our previous post about colostrum production, the timing of these hormonal changes is critical. The drop in progesterone and the rise in oxytocin not only trigger farrowing but also initiate colostrum production. This ensures that this vital “first milk” is available as soon as the piglets are born, a critical component of piglet survival.

However, it’s worth noting that while these hormonal changes trigger colostrum production, they don’t necessarily guarantee adequate colostrum volume. As we mentioned before, colostrum production can vary widely between sows and doesn’t necessarily increase with larger litter sizes.

Practical Implications for Producers

Understanding these hormonal processes can help us make better management decisions:

• Stress Management: Knowing that stress can interfere with hormonal processes and inhibit oxytocin release, we should strive to create calm, comfortable farrowing environments. This might include minimizing noise, ensuring target temperature and humidity levels in the room, and limiting unnecessary interventions.
• Timing of Interventions: If farrowing assistance is needed, understanding the normal hormonal progression can help us time our interventions more effectively. For example, knowing that prostaglandins help expel the placenta, we might be more patient in allowing this process to occur naturally before intervening.
• Colostrum Management: While we can’t directly measure or control hormone levels, understanding their role in initiating colostrum production can reinforce the importance of ensuring all piglets get adequate colostrum intake in those crucial first hours.

The Double-Edged Sword of Exogenous Hormones

As we deepen our understanding of the hormonal processes involved in farrowing, it’s natural to consider whether we can improve outcomes by intervening with exogenous (externally administered) hormones. While this approach offers potential benefits, it also comes with significant risks. Let’s examine both sides of this double-edged sword.

Potential Benefits:

• Farrowing Induction: Synthetic prostaglandins can be used to induce farrowing at a predetermined time. This can help with the timing of farrowing and ensure staff are available to assist if needed.
• Oxytocin Administration: In cases of prolonged farrowing, administering oxytocin can help stimulate contractions and potentially reduce the incidence of stillbirths.
• Colostrum Production: Some studies have explored using hormonal treatments to boost colostrum production, although results have been mixed.

Risks and Drawbacks:

• Disruption of Natural Processes: Farrowing is a finely tuned process. Interfering with it can lead to unexpected complications. The two biggest risks are improper timing and improper dosage. For example, inducing farrowing too early can interfere with normal processes resulting in less mature piglets with lower survival rates. Dosage is the other major challenge. Natural hormones are regulated through complex processes including internal feedback mechanisms that ensure appropriate balances are maintained. Exogenous hormones are often given in larger doses over shorter periods of time (imagine the difference between an injection and an IV drip).
• Oxytocin Overuse: While oxytocin can be beneficial, its overuse or misuse can lead to uterine rupture, increased stillbirths, or premature separation of the placenta. In my experience, oxytocin is one of the most over-used products in pork production.
• Masking Underlying Issues: Relying on hormonal interventions might lead us to overlook other important factors affecting farrowing success, such as nutrition, genetics, or environmental conditions.

The Balancing Act

Given these considerations, the use of exogenous hormones in farrowing management requires a delicate balancing act. While they can be valuable tools when used judiciously and under professional guidance, they should not be seen as a substitute for good management practices.

Instead of relying heavily on hormonal interventions, we should focus on optimizing the conditions that support natural hormonal processes. This includes providing appropriate nutrition, minimizing stress, and creating an environment conducive to successful farrowing.

If hormonal interventions are deemed necessary, they should be used selectively and with careful consideration of the potential risks and benefits. Always consult with your veterinarian to develop a protocol that’s appropriate for your specific situation. Some things to consider are:

• Ensuring protocols are customized for each application. For example, the Oxytocin dosage and timing for farrowing assistance and milk letdown may be different.
• Utilizing the minimum effective dose. While it may seem paradoxical, oftentimes lower doses are more effective and almost always come with less risk of side effects.
• If larger doses are required, consider split dosing (breaking up larger doses into smaller doses over a longer period of time).
• Consider different injection sites and methods.

As a general rule, we should default to letting natural processes run their course. While we should utilize the tools at our disposal, attempting to outsmart nature is often a fool’s errand. Our goal should be to worth with natural processes and, minimizing interference and eliminating unnecessary interference.

As research in this area continues, we may see the development of more targeted and safer hormonal interventions. However, for now, our primary focus should be on supporting and working with the sow’s natural hormonal processes rather than attempting to override them.

The Challenge of Measurement

Just as with colostrum production, one of our biggest challenges in this area is measurement. We can’t easily measure hormone levels in commercial settings, making it difficult to identify and address potential issues directly related to hormone imbalances.

This presents an opportunity for researchers and technology developers. If we could develop practical ways to measure or at least estimate these hormone levels in real time in commercial settings, it could open up new avenues for improving farrowing management and piglet survival.

In the meantime, we have to rely on behavioral and observable physiological clues of hormonal shifts. For example, when progesterone levels decline 24-48 hours prior to farrowing, we usually see:

• Nesting Behavior and Restlessness
• Frequent Urination and Defecation
• Udder Development and Evidence of Milk Letdown
• Slight Drop in Sow Body Temperature (1-2 degrees F)
• Reduced Appetite

As new technologies and tools are developed, it’s critical that we learn to effectively apply those technologies, but it is equally critical that we maintain high standards of traditional herdsmanship. While technology can be a powerful tool, it is no replacement for an experienced and skilled herdsman with superior observational ability and a functional knowledge of normal processes and behaviors.

Conclusion

While we may not be able to see or measure the hormones at work during farrowing, understanding their roles can help us appreciate the complexity of the process and inform our management decisions. As we continue to push for larger litters while simultaneously seeking higher survival rates, this understanding becomes increasingly important.

As always, while this information is valuable, it’s crucial to work closely with your consultants, veterinarians and breeding specialists to develop management and treatment protocols tailored to your specific farm needs. The balance of hormones during farrowing is complex, but by understanding the basics, we can better support our sows through this critical process.

About the Author: Todd Thurman is an International Swine Management Consultant and Founder of Swine Insights International, LLC. Swine Insights is a US-Based provider of consulting, training and advisory services to the global pork industry. To learn more about the company, send an email to info@swineinsights.com or visit the website at www.swineinsights.com. To learn more about Mr. Thurman’s speaking and writing, visit www.toddthurman.me .