Category: Choosing a Replacement Gilt

Choosing a Replacement Gilt – Reproductive Soundness

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There are a number of factors that are in play when looking at the reproductive soundness of a potential replacement gilt. No matter what, we all want our sows to be happy, healthy, and at the same time product healthy piglets. In this article we will discuss the various factors that a pig farmer or pork producer should look for when choosing a replacement gilt. If you haven’t read our previous article on Choosing a Replacement Gilt – Feet Evaluation and are interested in raising pigs for your own freezer or to send to market, I would recommend taking the time to read it. So let’s get started.

Reproductive Soundness – Underlines

The underline evaluation is another critical step in the evaluation of replacement gilt candidates. Each sow must have functional nipples to raise pigs and it appears that both genetics and selection play a role in determining the spacing, prominence, and location of the teats. As many of us know, these traits do have a direct impact on production and it is recommended that all replacement gilts are evaluated for reproductive soundness.

The ideal underline should have seven (7) or more functional nipples on each side and they should be well spaced and well developed. Blind or pin nipples should not be present. We all love our pigs but discrimination should be applies when fewer than seven functional nipples are present on each side, blind or pin nipples exist, there is poor spacing and/or placement is present, or inverted nipples are present. The initial screening of teat number, spacing, and quality can occur at birth, weaning, or in the nursery but the final evaluation should be made when the selection of breeding gilts occurs.

Unacceptable1-3 PointsFewer than six functional nipples on each side or presence of inverted nipples or poor spacing and prominence
Good4-7 PointsSix or more functional nipples on each side with adequate spacing and prominence
Excellent8-10 PointsSeven or more functional nipples on each side, well-spaced and well-developed with no pin or blind nipples.

Reproductive Soundness – External Genitalia

The external genitalia should also be evaluated on all replacement gilt candidates. Gilts should have a well developed vulva that is not tipped up.

  • Cull gilts having an infantile vulva.
    • These animals frequently have an under-developed reproductive tract.
  • Gilts having a small vulva should be avoided.
    • These gilts could have difficulty mating (particularly in a natural mating setting).
    • Once mated, these animals could have farrowing difficulties.
  • Tipped vulvas should be avoided
    • Tipped vulvas may contribute to a higher incidence of metritis and cystitis.

Injured vulvas should be avoided as they could impair mating. Once the injury is healed the scar tissue that develops could also cause farrowing difficulties. You can allow the injury to heal and make an assessment at a later date, but ensure you use caution if you choose to let the injury heal and retain the gilt as a breeding herd female.

Other genetic conditions to avoid

Gilts producting offspring with these traits or that are from litters with the following conditions should not be selected as replacements.

  • Scrotal Hernia – commonly called a rupture.
  • Atresia Ani – missing the anus.
  • Cryptorchidism – has at least one testicle that has not descended.
  • Hermaphrodite – has both female (vulva) and male (penis) reproductive organs.
  • Tremors – uncontrolled shaking.
  • Splayleg – at birth, legs are straddled to the sides and the animal cannot stand on its rear feet
  • Bent legs – pigs that have legs that have grown in an abnormal direction. Can be causedd by genetics or nutrition.
  • Polydactyly – pig is born with extra feet, legs, and/or dew claws.
  • Syndactyly – (mule foot), pig is born with one or more of its toes fused together.
  • Thickened forelegs = pig is born with one or both front legs that are unusually thick (approximately twice as thick as normal)


Increasing the number of traits that are evaluated and used as selection criteria increases the number of potential canidates taht are needed to achieve the desired number of replacements.

If gilts are home-raised, the number of candidate females needed to supply replacement gilts to the herd determines the number of grandparent females needed in an internal multiplication system. The number of gilt candidates may not be a large problem if producers are purchasing their replacement females. Hopefully, most , if not all, of the culling has occurred prior to delivery of the replacement gilts to the producers farm. However, purchase gilts should still be carefully scrutinized before a producer places them in the breeding herd.

I hope you found this article helpful and would love to hear your feedback. Please leave a comment below and if you did find it helpful please share it on social media.

Choosing a Replacement Gilt – Feet Evaluation

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This guide is to help anyone raising hogs for meat to effectively screen replacement gilt candidates before adding them into their breeding herds.  The visual appraisal can help you identify replacement gilts with various issues that can negatively impact sow longevity.  In this article I will discuss the conformation and structural soundness, feet and leg abnormalities, and reproductive soundness (underlines, external genitalia).

Identifying replacement gilts with one or more of these deficiencies and culling them, before they enter the breeding program, may be one of the keys to lowering breeding herd replacement rates and/or mortality rates. 

It doesn’t matter if you are purchasing replacement gilts or producing your own in an internal program, this guide provides examples of the types of problems that should be avoided when selecting replacement gilts.

Gilt Selection Guidelines

This guide covers the following criteria that are critical to the selection of functional females that will remain in the herd for a long and productive life:

Feet and Leg Soundness

  • Feet and leg problems represent the second largest reason for sows leaving the breeding herd.  This is particularly true for parity 1, 2, and 3 females.

Underline Soundness

  • Underlines should be visually evaluated and scored on ALL replacement females.

External Genitalia

  • Involves visually evaluating the vulva for size, shape, and injuries.

Feet and Leg Soundness

  • Feet and leg problems are one of the major reasons for culling sows and this is particularly true in parity 1, 2, and 3 females.
  • Feet and leg soundness should be evaluated on ALL replacement females.
  • Evaluation can involve a scoring process that is outlined in these documents.
    • Pork Industry Handbook fact sheet PIH-101: “Feet and Leg Soundness in Swine”
  • Gilts that score “poor” or “unacceptable” should be culled.

Other traits on which selection should occur for replacement gilts.


  • Gilts should be in the fastest growing 50-60% of the contemporary group.
  • Adequate growth increases the probability of proper reproductive development.
  • Slow growing females (within a group) can have delayed first estrus and may be lifelong problem breeders.


  • Backfat is important if replacement females are produced within the herd.
  • Consult NSIF Guidelines for Uniform Swine Improvement to obtain proper measurement and adjustment criteria.
  • Recommended levels of backfat are farm specific and may change due to genetics, environment, and end market.

Traits to Examine

There are a large number of criteria that can be used to evaluate a replacement gilt candidate.  The list below shows the traits that are desirable in a replacement gilt.

  1. Long bodied
  2. Smooth shouldered
  3. Deep bodied
  4. Deep, wide chest floor
  5. Trim jowl
  6. Correct set of knee
  7. Prominent, well-spaced underline
  8. Bold spring of rib
  9. Uniform level top
  10. Long level rump
  11. High tail setting
  12. Deep, long muscled ham
  13. Correct set of hock
  14. Heavy rugged bone
  15. Cushion to pasterns

What is desirable?

The ideal animal provides good cushion and flexion to the joints.  These animals will have an easier time getting up and down and will walk more fluidly.  They will also be less susceptible to stiff joints and arthritis as the result of constant stress on the joints.  Ultimately, these females are likely to remain in the breeding herd for a longer period of time.

Feet Evaluation

Start by evaluating the feet of the replacement gilt.  Large feet are desirable and should be out on all four corners with adequate width between them.  The individual toe size is also important so pay close attention to small inside toes, especially on the rear feet.  Examine all four feet for cracked hooves, foot pad abrasions, and other injuries.  It is critical to also evaluate toe size.  Leg conformation tends to conform to the shape and size of the toes.  The ideal toes are big, evenly sized, and spread apart.  The correct size and placement of the toes result in a better weight distribution.  If there is a difference of ½ inch or more in the toe size, the gilt should be culled.  When the toes are uneven there is a greater risk of cracked hooves and foot pad lesions as the animal becomes older.  Over time the size of the toe will have an effect on the mobility of the animal. 

                Small toes that have little if any spacing between them are considered undesirable.  If the toes are small then the weight is concentrated on a smaller surface area and there is a greater risk of cracked hooves and foot pad lesions as the animal becomes older and matures to heavier weights.  You want to make sure that you examine all potential gilts for the following feet and leg injuries before proceeding to other examinations:

  • Cracked Hooves
  • Foot pad abrasions
  • Other Injuries

Injuries can be very difficult to identify so take your time to examine them thoroughly.  If any animals have an injury be sure to have them treated to see if the injury improves.  If not, use caution if these females are retained in the breeding herd.  Ultimately production is an important aspect of producing pork but we all want the animals to live a comfortable and happy life.  If gilts are not selected for proper feet development it can lead to problems such as excessive toe growth once they enter the breeding herd.  Sows with these types of problems can lead to lameness and poor productivity and must be treated.  Gilts should be culled if the toe size differs greatly; focus on the inside toes.   If an obvious injury occurs that will impair timely mating or thriving in gestational environments, the gilt should be culled.  Also, injuries that will reduce gilt’s productive herd life are another reason for culling. 

That’s all for this post but in the next one we will discuss front leg evaluation and the things you want to look for. 

If you enjoyed this article or found it helpful please feel free to share it on your favorite social media platforms.


Kenneth J. Stalder, Associate Professor of Animal Science, Iowa State University

Colin Johnson, Extension Program Specialist, Iowa State University

Dale P. Miller, Editor, National Hog Farmer

Tom J. Baas, Associate Professor of Animal Science, Iowa State University

Nick Berry, Graduate Research Assistant, Iowa State Uninversity

Allen E. Christian, Swine Teaching Farm Manager, Iowa State University

Timo V. Serenius, Post-Doctoral Associate, Iowa State University

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