Breeding Basics - Catheter Types

Artificial insemination in swine has become such a common practice over the last 30 years that many almost take for granted the amount of science involved in the process. While the basic concept has remained constant since the beginning, the technology continues to evolve. New semen extenders, new single-dose protocols and new catheter styles are all being promoted in the quest to improve fertility results while using fewer and fewer sperm cells. I am often asked about the best catheters to use for AI in pigs. Let’s review the various styles.




The Melrose catheter is widely regarded as the original AI catheter in swine. While there were other tubes used in the early days of AI, this one was probably the most popular. It’s made of a heavy rubber-type material and is meant to be washed and reused. The spiral design on the end is meant to mimic the boar’s penis and to thread into the ridges of the cervix. I still run across farms in some countries using the Melrose catheter, but its use in the US is likely next to nothing. The design however was copied into the disposable spiral catheters that came next.

Disposable Spirette



The disposable spiral catheter (spirette) was introduced as a replacement for the Melrose. The advancement of being disposable eliminated the need to thoroughly clean and reuse thus reducing the possibility of introducing bacterial contamination during the insemination process. The catheter is turned counter-clockwise while pushing inward until it locks into the cervix. A gentle tug backward to ensure it is locked in place signals that you are ready to attach the semen bottle and begin breeding. Boar exposure and stimulation with back pressure, flank rubbing, etc. is necessary while applying gentle pressure to the bottle to initiate semen flow. The opening in the spiral end is to the side, which can sometimes be blocked by a cervical ridge and may require a slight repositioning of the catheter to allow semen flow. It is also difficult for the sow to draw the semen through the catheter by uterine contractions, necessitating the gentle pressure on the bottle to aid semen flow.

Foam Catheter



The foam catheter is by far the simplest and lowest cost style of AI catheter in the market. They come in many different foam shapes and colors, but the concept is the same. Rather than twisting as it’s being inserted as with the spiral catheter, the foam catheter is simply pushed into the cervix until it cannot go farther. A gentle tug backward to ensure it’s locked into place is all you need to begin breeding. The opening is on the end of the foam, which makes it much easier for semen to be drawn through the catheter by uterine contraction. Provide boar stimulation, back pressure, rubbing of the sides and flank and the sow should draw the semen in after a gentle squeeze to get things started.

Soft Disposable Catheters



The soft disposable catheters replace the foam end with a molded plastic piece with soft rings or collars to lock into the cervix. The concept is the same as the foam catheters. Simply push the catheter into place, tug back gently to ensure the lock and begin inseminating. As with the foam catheters, this style comes in various shapes and colors, but are somewhat more costly than foam.

IU (Intra-uterine) or PCAI (post-cervical) Catheters

In the late 1990’s we began work on catheters to pass through the cervix and allow insemination directly into the uterine body, eliminating loss of semen in the cervix and potentially reducing the amount of semen and number of sperm cells needed to achieve normal fertility and litter size. While the variety of available IU catheters continues to grow, they basically fall into two different styles.

Balloon-style IU Catheters



The balloon-style IU catheters are a normal foam catheter with a rubber extension on the inside of the tube which deploys when pressure is applied by squeezing the semen bottle. This extension is supposed to work its way through the cervix, finishing at the base of the uterus where the semen will ultimately be deposited. In our experience, the catheter works very well on some females. However sometimes the balloon does not deploy completely and the semen will not come out. Other times, excessive pressure causes the balloon to rupture and deposit the semen in the cervix. Also for many sows, the balloon isn’t nearly long enough to actually reach all the way through the cervix so even when it does deploy fully, it still isn’t achieving a true IU mating. When it does work properly though, it is very easy to use.


Cannula-style IU Catheter



The cannula-style IU (PCAI) catheters have become the standard IU catheter worldwide. As with other catheter styles, they come in a variety of shapes, sizes and colors, but the basic concept is the same. First, a standard catheter (either foam, soft rubber or spiral) is inserted and locked into the cervix. Secondly, an inner cannula is inserted through the inside of the standard catheter and pushed inward until it passes all the way through the cervix. Once the cervix is passed, the semen bottle is attached to the inner cannula and the semen is squeezed through the cannula into the base of the uterus. Both catheters are removed simultaneously immediately after the semen is deposited. This technique is done without stimulation and without the presence of a boar in order to make passing the cervix more probable. Our research and experience with this technology over a period of nearly 20 years indicate that conception and litter size are equal (not superior) to normal AI when using a normal semen dose (70-100ml with around 3 billion cells). The benefit when using a normal semen dose is that IU insemination is typically much faster. Our research and experience also indicate that normal fertility and litter size can be achieved with this technology using half as much semen (35-50ml with around 1.5 billion cells) or potentially less. That is where there is a true benefit. However in order for this to be achieved, one needs to be certain that the female receives a true IU mating and that the cannula actually passed the cervix.

What’s the Difference?

With all these choices for AI catheters, how does one decide which to use? Which one is the best? Let’s start with the basic AI catheter first (traditional AI). In commercial US swine production, the foam catheter is far and away the most popular option. Why? It’s relatively cheap, easy to use and very effective. In the showpig world, the spiral catheter is still very popular. While we typically recommend the foam, there is nothing wrong with using the spiral catheter if that’s what you are more comfortable with. You can achieve the same fertility results with either. The soft disposable catheters will also work equally well. There is no real difference in function because of color or style. There are a few details to be aware of however.

Length and Diameter

We manufacture our catheters to a standard length of 22 inches. That ensures that the length is appropriate for nearly every sow. When using a shorter catheter on big older sows, you may find yourself attaching the semen bottle right at the vulva, which makes breeding a bit more difficult. Also we manufacture to very tight specifications for inside and outside diameter of the catheter tube. This ensures that whether your semen is packaged in a bottle, tube or bag, you should get a tight fit when attaching the semen package to the catheter.

Adaptor or no Adaptor

Catheters are typically available with the option to have a rubber adaptor on the end. The adaptor helps ensure that the semen package fits tightly into the catheter tube. Many also have a plug to allow leaving the catheter inside the sow after insemination for a few minutes of extra stimulation without allowing semen to leak back out through the catheter. As long as the diameter is right on the catheter tube, the adaptor is not really necessary, however this can be a personal preference. It does add a few cents of cost.

Quality Control

Having personally worked in China with a number of supply manufacturers, quality control of AI products is a primary concern. There is an abundance of Chinese plastic manufacturers that market very cheap products of very low quality. Variation in length, diameter, foam quality, and most importantly, cleanliness are very big concerns. US AI product suppliers mostly purchase AI catheters from Chinese suppliers, so it’s important that your supplier has a very good QC protocol in place both at the factory and on the US side. Once during a factory tour in China, I witnessed a pile of foam sheets being dragged one-by-one from an outdoor gravel driveway, through the mud, in the rain and onto a band-saw where they were subsequently cut into blocks, drilled and ground into shape and promptly glued onto catheter tubes. They were placed directly into a logo bag of a US AI supplier and put into a box.

IU (PCAI) or Not?

There has been a lot of misinformation spread about IU (PCAI) insemination. First of all, I continue to refer to it as IU (intra-uterine) despite the industry accepting the PCAI (post-cervical artificial insemination) term. When we began this in the 90’s it was commonly called IU. For me the term “post” is more properly used in reference to time, not in reference to position. While I understand the idea is to say that insemination is being done “beyond” or “after” the cervix, I don’t believe “post” is the correct term to describe this. Anyway, that’s just me.

More concerning to me is some of the misinformation I hear from clients or read on the web. Please take note. No, you will not get good fertility with poor-quality or old semen because you are using an IU catheter. Using IU or PCAI does not improve fertility with a normal dose of semen, much less a poor dose. No, you cannot use a single insemination because of using IU or PCAI catheters. If you want to use a single-dose protocol, you’ll need to use Ovugel or otherwise adjust your insemination timing to try to time your insemination just prior to ovulation. No, you do not change the timing of your insemination because of using IU or PCAI catheters. Use the same timing protocol you use with a standard catheter. No, you will not see better conception rate and litter size by using IU or PCAI catheters. If you do, it’s because you were doing a poor job of using standard catheters in the first place. Yes, you can get good fertility using a smaller dose with fewer sperm cells using IU or PCAI catheters.

So why use IU catheters? Once you know the sow is in heat, you don’t need the boar present to breed. Breeding is generally faster and more foolproof. You can utilize fewer sperm cells (breed more sows with the same boar).

Differences between IU Catheters

The style of outer catheter used with the inner cannula doesn’t really matter. The primary differences between the different IU catheters are length, diameter, stiffness, connector and tip. In our experience a length of 8.5 inches is the minimum required beyond the end of the outer catheter to ensure that the cervix can be passed on even the largest, oldest sows. Our IU cannulas are 31 inches long and our catheters are 22 inches, so there is a 9 inch extension with which to pass the cervix. Generally speaking, the smaller diameter the better because the cervix on some females can be very tight. However, the cannula also has to be the right combination of stiffness and flexibility to push and maneuver through the cervix without getting stuck or doubling over. The connector on the back end needs to connect easily to tubes, bottles and bags without leaking. The tip needs to be smooth and slick to easily navigate the cervix without causing damage. The tip can have the holes out the sides or directly in the end for the semen to be deposited into the uterus. The style of tip really makes no difference as long as it is small and smooth. The outer diameter of the cannula should match the inner diameter of the outer catheter tip to hold the cannula tightly when inserted. Some also come with an extra connector on the bottle end to hold the cannula tightly inside the outer catheter. This isn’t really necessary either.

If you are interested in trying IU catheters, start with a supplier you trust that will help you implement the technique. Try different styles until you find one that you are comfortable with. Keep in mind that what really matters is being able to completely pass the cervix with the inner cannula. If you can pass the cervix you will be successful. The rest is just noise.


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