It’s no secret that lameness and locomotion problems are major reasons why sows are culled from a herd. The good news is that knowledge and understanding of sow lameness continues to grow as more researchers collect and report new data in search of answers.

University of Minnesota surveys have shown that more than 88 percent of sows have at least one claw lesion. Of course, not all lesions cause lameness and reduced sow productivity. So, which ones really matter? How do the lesions form, and what can be done to decrease their prevalence and severity? Let’s take a look.

The most common lesions within a herd can vary based on several factors, including management, nutrition and genetics. “The lesions of greatest concern are those which penetrate the horn wall into the corium of the foot, causing an inflammatory response, since these types of lesions cause pain and locomotion problems for sows,” says John Deen, DVM, University of Minnesota researcher. Examples of such lesions include white-line lesions, horizontal and sidewall cracks, and overgrown toes and dew claws.

The white line is the natural junction between the elastic heel and the more rigid wall. There are many reasons why white-line lesions occur, including mechanical factors (pressure from overgrown heels or torsion), inflammation and inferior horn (nutrition deficiency), Deen notes. 

White-line Lesions

Treatments include:

  • Antibiotics should be administered for infected wounds to control bacteria. The exact antibiotic and treatment recommendations should come from your herd veterinarian.
  • Feed highly bioavailable forms of trace minerals to help improve the claw horn’s overall resilience.

Horizontal Cracks

These lesions are most often caused by trauma due to inferior flooring, such as faulty slats and slippery surfaces. Horizontal wall cracks initially appear as linear hemorrhages at the coronary band, Deen says.

Treatments include:

  • Take measures to reduce trauma by improving floor surfaces.
  • Feed highly bioavailable forms of trace minerals to help improve the claw horn’s overall resilience.

“Sidewall cracks run vertically or obliquely from the ground surface in the sidewall up toward the coronary band, along the junction between the soft heel and the far harder wall horn,” Deen points out. These cracks are often associated with heel overgrowth. “They can be painful when the crack is deep enough to pinch the corium or serve as an entry point for bacteria, causing infection or inflammation,” he adds.

Sidewall Cracks

Treatments include:

  • Administer antibiotics to control bacteria and prevent infected wounds.
  • Trimming an excessive horn may alleviate abnormal pressure.
  • Feed highly bioavailable forms of trace minerals to help improve the claw horn’s overall resilience.

Overgrown claws can develop from inadequate wear or chronic inflammation. Problems surface when toes and dew claws lengthen to the point where they hinder the animal’s movement or cause mechanical injury to the soft tissues at the coronary band, Deen says. Horizontal, parallel hemorrhages are often seen with this condition. Also, the horn capsules can be torn off when they are caught in a slat, causing extreme pain. 

“Inflammation may be due to perforation of the capsule from excessive wear, bruising of overgrown heels, laminitis or abscesses within the claw that lead to elevated metabolic activity and excessive horn growth,” Deen adds.

Overgrown Toes/Dew ClawsTreatments include:

  • Take measures to reduce trauma and insufficient wear by trimming surplus wall and heel horn and improving the flooring.
  • If dew claws are torn off or broken, this can leave the corium exposed to bacteria and infection risk. If infection occurs, administer antibiotics as your veterinarian recommends.
  • Feed highly bioavailable forms of trace minerals to help improve horn quality.

Identifying lesions and understanding how each type develops helps narrow the possible causes s and can guide corrective action. Although a lesion’s development can be quite  involved, most occur from three sources: inflammation, trauma and mechanical factors, probably in conjunction with an inferior horn. It can take several weeks or months after the initial trauma or deficiency for lesions to appear on the surface of the claw capsule.

While lesion scoring and clinical diagnosis is helpful, they do not necessarily correlate with post-mortem exams because:

  • Lesions do not always extend deeper into the claw than the horn layer to cause pain or discomfort.
  • Some lesions are only revealed once the claw has been dissected.

More recently, research has shown that highly available forms of the complexed trace minerals zinc, manganese and copper play a critical role in building strong, healthy feet. For example, when zinc, manganese and copper as amino-acid-complexed minerals were supplemented to sows in a controlled experiment, claw lesions decreased in sows housed in gestation crates, according to research by Sukumaran Anil, University of Minnesota veterinary doctorate student. 

The sows were fed identical gestation and lactation diets except for the zinc, manganese and copper source. Sows were fed diets containing a partial substitution of the inorganic-trace minerals with amino-acid-complexed minerals (50 ppm of zinc, 20 ppm of manganese, 10 ppm of copper). The rest of the supplemental trace minerals were provided by inorganic-sulfate sources that also were used in the control diet (125 ppm of zinc, 40 ppm of manganese and 15 ppm of copper). 

The sows fed trace minerals as amino-acid complexes had fewer lesions on the hind feet than the control sows.  They had fewer lesions on the lateral claws and fewer total lesions. Lameness prevalence was lower for the sows fed trace mineral amino-acid complexes (34 percent versus 51 percent) compared with sows fed inorganic trace minerals, Anil reports. Lesion-severity scores also were lower when sows received diets with trace minerals as amino-acid complexes.

In the same experiment, sidewall cracks involving group-housed sows showed those fed trace-mineral-amino-acid complexes had more lesions that either improved or held steady compared with the controls (91 percent versus 73 percent), Anil reports.

In even more recent research, Anil has found an association between claw-lesion scores, lameness and gestation-housing systems. The study found that in both the group- and stall-housing systems, a high score for sidewall vertical cracks increased the lameness risk factor. Group-housed sows had higher lesion scores in all claw areas compared to sows in stalls.

Across both housing systems, the University of Minnesota research found that for each change in the lesion score (such as moving from 1 to 2) you can expect the following corresponding lameness increases:

  • Overgrown claws = a 13 percent increase for each scoring unit increase;
  • White-line lesions = a 20 percent increase for each scoring unit increase;
  • Sidewall lesions = a 17 percent increase for each scoring unit increase.

This may not be the case in all production systems, but it does signal which lesions have the most impact. “There are a lot of lesions. Try to focus on those that are more likely to lead to lameness,” says Mark Wilson, reproductive physiologist with Zinpro Corp.

Other advice he offers: “You need to evaluate lesions to understand what’s causing them, as well as what are the options to prevent them. This is important from a welfare and productivity standpoint.” He adds, “So, work to identify, understand and prevent the lesion situation on your farm.”