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.
- Underlines should be visually evaluated and scored on ALL replacement females.
- 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”
- National Swine Improvement Federation Guidelines for Uniform Swine Improvement available at the following website http://www.nsif.com/guidel/guidelines.htm
- 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.
- Long bodied
- Smooth shouldered
- Deep bodied
- Deep, wide chest floor
- Trim jowl
- Correct set of knee
- Prominent, well-spaced underline
- Bold spring of rib
- Uniform level top
- Long level rump
- High tail setting
- Deep, long muscled ham
- Correct set of hock
- Heavy rugged bone
- 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.
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.
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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