Most sows hit their breeding peak between the third and fifth litters, then gradually decline. By parity 7 or 8 (roughly 3.5 to 4 years of age), litter size, piglet survival, and the sow’s physical condition typically drop enough that breeding her again costs more than she returns. In commercial herds, the average sow is culled after just 3 to 4.6 litters, though well-managed sows on smaller operations can sometimes go further.
When Litter Size Starts to Drop
A sow’s productivity follows a clear arc. First-litter gilts average around 10.5 to 11 live-born piglets. That number climbs through parities 2 to 5, peaking at roughly 11.3 to 11.4 piglets born alive in the fourth and fifth litters. After parity 5, the decline begins. By parity 7, live births drop back to about 10.5, and sows at parity 8 or beyond average under 10.2 piglets born alive, which is actually lower than a first-litter gilt.
This pattern is consistent across studies and holds regardless of management system. The biological reason is straightforward: the uterus accumulates wear over successive pregnancies, ovulation rates may remain high but embryo survival drops, and the sow’s body has less capacity to support large litters. A sow that consistently farrows fewer piglets than a replacement gilt is costing you money with every cycle.
The Economics of Keeping Her
To break even on the cost of raising or purchasing a gilt, a sow generally needs to complete at least three litters. That means culling before parity 3 is almost always a financial loss unless the sow has a serious health or reproductive problem. The profitable window runs from parity 3 through 5 or 6, where litter sizes are largest, piglet birth weights are heaviest, and the sow’s feed efficiency for milk production is strongest.
In U.S. commercial herds, 50 to 69% of sows are culled by parity 4, with an average culling parity of just 3 (around 23 months of age). That number is surprisingly low and reflects the aggressive replacement strategies of large operations, where keeping herd productivity high matters more than maximizing any individual sow’s lifespan. Smaller farms with lower replacement costs or proven sows often keep them through parity 6 or 7 before retirement.
Physical Signs a Sow Should Stop Breeding
Age alone isn’t always the deciding factor. A sow’s body condition tells you more than her parity number. The main physical reasons sows get culled, in order of frequency, are reproductive failure (34 to 44%), leg and joint problems (12 to 27%), and poor productivity (7 to 18%). Udder problems account for 6 to 18% of culls and become more common in older sows.
Watch for these specific signs that a sow has reached her limit:
- Lameness or stiffness: Difficulty standing, reluctance to bear weight evenly on all four legs, or swollen joints. Leg problems worsen with each pregnancy because of the weight load, and a lame sow crushes more piglets.
- Poor udder condition: Blind teats (non-functional), scarred or inverted nipples, or signs of past mastitis. A sow that can’t nurse 10 or more piglets effectively limits the litter she can raise.
- Failure to cycle or conceive: If a sow doesn’t come back into heat within 7 to 10 days after weaning, or fails to conceive after two breeding attempts, her reproductive system may be done.
- Thin body condition that doesn’t recover: Older sows that can’t rebuild body reserves between weaning and the next breeding will produce smaller litters and weaker piglets each cycle.
Breed Differences in Longevity
Not all sows age at the same rate reproductively. Landrace sows tend to last longer than Large White (Yorkshire) sows, completing an average of 0.56 more parities and living about 92 days longer in productive life. The average productive lifespan was roughly 596 days for Landrace sows versus 503 days for Large White.
For Large White sows, the risk of being culled stays relatively stable through parities 2 to 4, then climbs from parity 6 onward. Landrace sows show a similar low-risk period for the first three parities, with culling risk rising from parity 4. Heritage and rare breeds used on smaller farms, such as Berkshire, Gloucestershire Old Spots, or Tamworth, are often anecdotally reported to breed productively for more litters, but hard data comparing them to commercial lines is limited. If you’re raising a heritage breed, use the same physical assessments described above rather than relying on fixed parity cutoffs.
What About Colostrum and Piglet Quality?
One concern with older sows is whether their piglets get a weaker start in life. The data here is reassuring up to a point. Antibody levels in colostrum (the critical first milk) don’t decline significantly with parity. Experienced sows actually produce more total colostrum and milk than gilts, because they aren’t diverting energy toward their own growth. Fourth-parity sows produce the highest volume of milk, and their colostrum tends to be richer in certain protective antibodies compared to first-litter mothers.
Where older sows do fall short is piglet birth weight consistency. Litters from sows at parity 8 and beyond tend to have more variation in piglet size within the litter, which means more runts and higher pre-weaning mortality. Even if an older sow farrows a decent number of piglets, more of them may be too small to compete at the udder.
A Practical Breeding Cutoff
For most operations, parity 6 to 8 is the realistic upper limit, with the sweet spot for culling falling between parity 6 and 7. A sow that reaches parity 6 in good body condition with sound legs, functional teats, and consistent litter sizes above 10 live-born piglets is still earning her keep. A sow at parity 5 that’s lame, thin, or dropping below 9 piglets born alive is already past her useful breeding life regardless of her age.
The simplest rule: compare her last litter’s performance to what a replacement gilt would give you. If an older sow’s production has dropped to first-litter levels or below, and she’s showing any physical wear, it’s time. Keeping detailed records of litter size, born-alive counts, and weaning weights for each sow makes this decision straightforward rather than emotional.