If you have been around horses very long you know that horses love to hurt themselves a lot and when they do it’s many times on their lower extremities. This is the favorite place for a horse to grow proud flesh or as veterinarians call it exuberant granulation tissue. Many people think of granulation tissue or proud flesh as a negative outcome of wounds but as I will explain it does have a purpose in helping the horse heal. Unfortunately it doesn’t always behave the way we want it to and sometimes it’s both the horses and the peoples fault when it comes to taking care of these wounds.
Phases of Wound Healing
There are three main phases of wound healing in the horse. These phases are inflammatory phase, proliferative phase and maturation/remodeling phase. Inflammatory phase occurs within in minutes and last for hours after a wound is created. In the inflammatory phase, swelling, hemostatsis and migration of white blood cells to the wound is initiated. This inflammatory phase is one of the most important steps in setting the stage for the rest of the phases. Granulation tissue is part of the natural healing process for wounds in horses during the proliferation phase. It becomes present in the wound bed of horses around 5-7 days after the wounding occurred. This tissue is made up of fibroblasts and lots of new blood vessels that form from the edges of the wound. This tissue will fill in the gaps between the wound and will convert part of the cells to myofibroblasts. These myofibroblasts have very small microscopic muscle fibers that help pull the wound edges closer together during what is called contraction. Contraction occurs around 10-14 days after wounding and this helps reduce the size of the wound by up to 40-80% to allow the rest of the wound to be healed by epithelialization. The last phase is when the wound strengthens by the replacement of poorly organized collagen tissues with more organized, cross-linked and better quality collagen tissue.
Where It Goes Wrong
There are many reasons horses heal slowly especially on their extremities but the difficulty in wounds in horses and granulation tissue lies in the fact that horses don’t produce a very good inflammatory phase when the wound is created. This phase becomes mediocre and prolonged compared to other animal species and even when compared to ponies. This phase seems to be the key to jump starting the healing process and horses just don’t do it very well and because they get stuck in this prolonged inflammatory phase leads to proud flesh formation.
Other factors that lead to poor wound healing in the lower limbs of horses are that they don’t have muscle tissue in the limbs that help provide blood supply to the wound. Limb wounds tend to be dirtier and contaminated because it is closer to the ground. Motion is also a problem on the limbs especially when wounds occur over a joint that is a high motion point of the limb. Blood supply is also a factor in wound healing in horse’s legs and is just not as good as in the upper part of their bodies.
How We Make It Worse
Many times part of the reason wounds grow so much proud flesh is because of the things that are applied to the wounds. Some of most harmful products to wounds are caustic wound powders or wonder dusts that claim to burn back and destroy granulation tissue. The problem with these products is they cause more inflammation and are indiscriminate at what they destroy in the wound such as the newly formed and very delicate skin that is coming across the wound. Some antimicrobial wound dressings have been shown to delay wound healing through research and should not be used in certain stages of the wound healing process. Lastly wound dressings that are too occlusive can cause the wound to be starved of oxygen and lead to more proud flesh production.
Managing and Minimizing Proud Flesh
Proud flesh can lead to delayed wound healing because the new cells growing from the edge of the wound cannot migrate up over a mound of granulation tissue as well as they can over a flat wound bed. One method of managing granulation tissue when it does become too proud is by sharply cutting it flat with a scalpel blade. This removes the excessive tissue and refreshes the wound to encourage proper healing. Another method is by medical treatment of granulation tissue with topical steroids which also helps reduced the production of excessive granulation tissue and keeps the proud flesh from forming, but when used too much can lead to delayed wound healing.
There are studies that have compared wound dressing ointments and recently a study found that triple antibiotic wound ointment (Neosporin) produced the least amount of proud flesh when compared to others. Another very safe and effective wound ointment is SSD or silver sulfadiazine wound ointment often used for burn wounds in people. Even honey specifically Manuka honey wound dressings or ointments help improve wound healing.
Biological products such as amnion can help reduce proud flesh and improve wound healing. Amnion is tissue that surrounds the fetus in the womb and is rich in stem cells, growth factors and anti-inflammatory cytokines that help reduce scar tissue and promotes healing. Another biological produce produced from the bladder of pigs called A-cell has been applied to wounds to promote better healing. Skin grafting wounds are also a very good way to reduce the wound size or even completely cover the wound to get it healed with new skin cells. There are many methods and techniques to graft skin in horses and often is dictated by the size, shape and location of the wound.
Take Away for Horse Owners
- Clean the wound as soon as possible with mild soap and water or diluted betadine solution products.
- Often it is recommended to have wounds examined as soon as possible by a veterinarian especially if the wound is over a joint or other important structures.
- Closing the wound if possible with sutures will help reduce having proud flesh.
- Using appropriate wound dressings and ointments that your veterinarian advises. The rule of thumb is if you can’t put the ointment in your eye it is not safe for a wound.
- If proud flesh begins to form have it cut off or have your veterinarian prescribe a steroid cream such as triamcinolone or betamethasone to help safely shrink down the granulation tissue.
- Skin grafting is another method to cover a wound more quickly with new skin to reduce granulation tissue formation.
The approach to dealing with wounds and proud flesh is rather simple one and doesn’t require a magic ointment or treatment to keep it under control. Remember that the goal is to keep in under control early on and to avoid things that are used on the wound from making it worse. If you are concern that your treatment or care is not working for your horse please reach out to your veterinarian for help.
Read more in the July 2021 issue of Oklahoma Farm & Ranch.