Why Your Pigs Have Small Litter Size and What You Can Do About It


Why Your Pigs Have Small Litter Size and What You Can Do About It


Over the last year or so, one of the biggest issues we’ve struggled with on my farm is small pig litter sizes.


This is a relatively new problem. We went from many years where litters averaged 10 piglets or more (usually more), and then all of a sudden, we were down to 7 and then just 5 piglets being born at once.

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Small litters in pigs are problematic for several reasons. For us, the biggest issue is that we raise pigs for meat to sell to other customers, as our farm is also a business.


It’s also important to note that small litters are just as stressful and taxing to a sow’s system as big ones, meaning there’s no benefit at all to having fewer piglets.

We were able to get to the heart of our problem – and that’s why I want to share this information with you today. Hopefully, small litters in pigs is something you’ll never have to deal with – but if you do, this article will walk you through the issue to help you troubleshoot.


What is the Average Pig Litter Size?

The average litter of pigs is around 7-8 piglets. It’s not uncommon for a sow to have up to 14 pigs per litter, however.

Pigs are quite prolific. A single sow can have 2 litters of pigs per year (though this isn’t always recommended as pregnancy can be quite taxing on her system).

It’s natural and completely normal for pig litter size to fluctuate. Just because a sow had 10 piglets 1 year doesn’t mean she’ll have 10 the next.


If litters are small for several years in a row, there’s a good chance that something is going on. This is especially true when it comes to breeding older pigs (sows) versus younger, first-time mothers (gilts).

Also, if your pig has fewer than 4 pigs per litter that’s a major red flag regardless of your pig’s age or any other variables. It requires at least 4 fetuses to maintain a pregnancy, so fewer than that number of piglets born indicates that fetuses died in utero after they were implanted.

READ ALSO: A Pig Farmer’s Guide to Identify, Treat, & Prevent Mycoplasma Arthritis

What Determines the Number of Piglets Per Litter?


There are a few factors that go into how many piglets will be born in each litter.


1. Age of the Pig

Litter size is almost always the smallest in the first litter, with the largest number of piglets born in the third and fifth years. This remains constant and then starts to decline as the pig gets older.


2. Genetics and Breed

The genetics of animals play a huge role in how many piglets are born. If a gilt’s mother was a prolific breeder with large litters, there is a stronger chance (though not definite) that the gilt will have large litters, too.

For the most part, purebred animals of some breeds have smaller litters than those of commercial breeds.

Certain pig breeds have been selected for genes related to litter size. Chinese pig genetics tend to be the most prolific.

Of course, you can always select within your herd for larger litter sizes.


3. Diet

Nutrition is one of the most important factors to consider when it comes to small litter sizes. If pigs are underfed or of a poor body condition score (too thin or too overweight), it can reduce how many eggs are produced and therefore, how many piglets are born.

Feeding a high-quality diet at all times, but specifically within 10 days of breeding can maximize the ovulation rate and litter size. Deficiencies in vitamins A, E, and biotin are the most closely linked to small litter sizes.

That said, overfeeding gilts within the first 3 days of breeding can reduce the rate of embryo survival, so it is a delicate balance that you will need to strike.


4. Health

Of course, the overall health of a pig influences litter size, too. Pigs that are in good body condition and aren’t suffering from parasites or any diseases are more likely to produce large litters.


What Can Cause a Too-Small Litter?

There are a few factors to rule out when you are trying to increase the number of pigs per litter. Here are some things you can consider when you’re trying to figure out why your litters are too small.


1. Genetics

I already mentioned genetics but it’s worth mentioning again. If you can, select gilts based on ovulation rates (which can be tough to calculate, but possible) as well as their mother’s histories.

Maintaining a farrowing line that is more fertile and productive can help address this issue in your herd. While it can be difficult, sows that produce small litters need to be culled.


2. Worms

Get your pigs on a good deworming regimen. Heavy parasite loads often cause fertility issues in pigs and can lead to other lingering reproductive issues as well.


3. Diseases

There are all kinds of reproductive diseases that can cause small litters in pigs. The most common include parvovirus or PRRS.

Both can cross the placenta and infect the litter, causing piglets to die in utero or immediately upon birth. You might suspect these diseases if your piglets are born mummified or if litters are small in general.

Fortunately, most reproductive diseases can be prevented with vaccinations.


4. Low Environmental Temperatures

Low light conditions and irregular temperatures have often been linked to small litters, too. If you can, try to breed your animals when the weather is not too hot or too cold.


High ambient temperatures have been linked to reduced boar fertility and smaller litter sizes.


5. Poor Mating

When mating your sows and gilts, make sure you do it in the middle of standing estrus (about 20 hours from the beginning) and repeat after 24 hours.

If you’re breeding a boar and a sow, make sure you are culling sows who produce small litters. The same goes for any boars if you can identify them as the problem (it usually has to do with poor semen quality).

When relying on artificial insemination, check the semen as well as the techniques. Shipping issues can sometimes be to blame. The semen quality as well as the timing of insemination both need to be perfectly in line to produce adequately-sized litters.

Young boars can be used for up to 4 consecutive services per week, while mature ones can be used for 6 services per week. Make sure you’re considering your stocking densities and don’t overuse your boars.

A Few More Tips to Help Increase Pig Litter Size

Here are a few more tips to consider as you try to up your litter size.


1. Check the Feed

First and foremost, consider what you’re feeding your animals. When we got down to the nitty-gritty of why our sows weren’t having enough piglets, we were able to figure out that the issue was a vitamin deficiency in feed.

We switched to another feed with better vitamin and mineral ratios, and the problems went away. Always look at the feed before you attempt to switch up anything else in your sow management plan.


2. Prevent Diseases

Again, do everything in your power to keep your pigs healthy. Keep the housing areas clean and make sure your sows and boars are both on a solid regimen when it comes to vaccinations and deworming.

Cull animals who continuously suffer from these diseases despite proper management.


3. Rethink Farrowing Systems and Housing

If you’re housing pigs together in group housing systems, you may find a reduction in litter sizes. More than 20 animals living together, for whatever reason, is correlated to smaller litters.

Also, don’t move your sows within the first 28 days of service. This can lead to stress that causes abortions.

You may have to consider how often you’re attempting to breed your pigs as well. Although the average lactation length (18-28 days) doesn’t usually impact litter size, a sow that weans her piglets too early or too late might not be quite as prolific during the next gestation cycle.

Finally, when your sow farrows, consider whether there are ways to reduce piglet mortality. Although this post focused mostly on litter sizes that were small from the get-go, some people consider small litter size as it relates specifically to piglets dying right after they are born.

Often, this has to do with a sow rolling on her piglets. Using a farrowing crate or another farrowing management system can help, but these tend to be highly controversial. Do what’s best for your farm but consider all the alternatives.


Improve Pig Litter Size

Improving the size of your pig litters isn’t always easy, but it can be done. However, it’s important to have realistic expectations.

Some farmers assume that because it is technically possible for a pig to have 2 dozen or more piglets – the largest litter ever was 27 – that doesn’t mean it’s common. It’s also not necessarily ideal. Often, in large litters like this, many of the piglets aren’t large enough or healthy enough to survive.

Keep your expectations under control and follow the tips above to optimize the health of your pigs!

Contributed by Rebekah Pierce

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