Bovine Trauma and Skin Wounds – NAVLE Study Guide

Overview and Clinical Importance

Traumatic skin wounds are commonly encountered in bovine practice, resulting from barbed wire injuries, horn wounds, equipment injuries, animal bites, and husbandry procedures. Unlike horses, cattle have thick, relatively inelastic skin that presents unique challenges and advantages for wound management. Understanding wound healing principles, appropriate closure techniques, and potential complications is essential for NAVLE success and clinical practice.

Cattle skin is notably thicker than that of horses or small animals, often described as "leather-like" in texture. This thickness requires specialized suture materials and techniques but also provides excellent resistance to wound contamination when intact. The economic considerations in bovine practice often influence treatment decisions, making efficient wound management particularly important.

Wound Classification

Types of Traumatic Wounds in Cattle

Wound Classification by Contamination Level

Wound Healing Phases

Wound healing in cattle follows three overlapping phases. Understanding these phases is critical for appropriate wound management timing and recognizing healing abnormalities.

Phase 1: Inflammatory Phase (Days 0-5)

Hemostasis: Immediately after injury, vasoconstriction occurs followed by platelet aggregation and fibrin clot formation. This provides temporary wound closure and establishes the scaffold for cellular migration.

Inflammation: Vasodilation follows within minutes, allowing inflammatory cell infiltration. Neutrophils predominate initially (peak 24-48 hours), followed by monocytes that differentiate into macrophages. These cells perform phagocytosis and release cytokines and growth factors essential for repair.

Clinical Signs: Heat, redness, swelling, and pain are normal during this phase. Prolonged inflammation (greater than 5-7 days) indicates complications.

Phase 2: Proliferative Phase (Days 3-21)

Granulation Tissue Formation: Fibroblasts proliferate and deposit collagen (primarily Type III initially). New capillaries form through angiogenesis, creating the characteristic red, granular appearance.

Epithelialization: Epithelial cells migrate from wound edges across the granulation tissue bed. This occurs within 48 hours in clean surgical incisions.

Wound Contraction: Myofibroblasts cause centripetal wound contraction, reducing wound size. This is more pronounced in cattle compared to horses.

Phase 3: Remodeling Phase (3 Weeks to 1-2 Years)

During remodeling, Type III collagen is gradually replaced by stronger Type I collagen. Collagen fibers reorganize along lines of tension. Maximum tensile strength (approximately 80% of original) is achieved by 12 weeks. The wound scar continues to mature for up to 2 years.

Types of Wound Closure

Primary Intention (First Intention)

Definition: Immediate wound closure with sutures, staples, or tissue adhesive.

Indications: Clean wounds less than 6 hours old; minimal contamination; adequate tissue for apposition; controlled surgical incisions.

Advantages: Fastest healing; minimal scarring; lowest infection risk when appropriate.

Delayed Primary Closure

Definition: Wound closure 3-5 days after injury, before granulation tissue forms.

Indications: Moderately contaminated wounds; wounds requiring observation for viability; uncertain tissue perfusion.

Management: Daily wound care and monitoring; closure when clean and healthy tissue confirmed.

Secondary Intention (Second Intention)

Definition: Wound left open to heal via granulation, contraction, and epithelialization.

Indications: Heavily contaminated or infected wounds; excessive tissue loss; wounds greater than 12 hours old; insufficient skin for closure.

Management: Daily lavage and bandage changes; debridement as needed; antimicrobial therapy for infection.

Secondary Closure (Third Intention)

Definition: Wound closure greater than 5 days post-injury, over healthy granulation tissue. Used when initial contamination prevented primary closure but granulation tissue now provides a healthy bed for delayed suturing.

Wound Management Protocol

Initial Assessment and Stabilization

Before focusing on the wound, assess the animal for systemic stability. Hemorrhage control takes priority. Determine wound age, mechanism of injury, contamination level, and structures involved. Cover wounds with sterile dressing during initial evaluation to prevent further contamination.

Wound Preparation

Hair Removal and Skin Preparation

Apply sterile lubricant (KY jelly or saline-soaked gauze) to the wound to prevent hair contamination. Clip hair at least 5 cm from wound margins. Surgically scrub surrounding skin with chlorhexidine (2%) working outward from the wound. Avoid getting antiseptic solutions in the wound.

Wound Lavage

Solution: Sterile isotonic saline (0.9% NaCl) or lactated Ringer's solution are preferred. Dilute chlorhexidine (0.05%) may be used for contaminated wounds but can be cytotoxic to fibroblasts at higher concentrations.

Pressure: Optimal irrigation pressure is 7-8 psi (achieved with 35 mL syringe and 18-gauge needle, or 1-L bag at 300 mmHg pressure). This removes bacteria without tissue damage.

Volume: Use 500 mL to 1 L minimum for most wounds. Volume is more important than solution type.

Debridement

Surgical debridement involves sharp excision of nonviable tissue using a scalpel or scissors. Remove all necrotic tissue (dark purple/black, non-bleeding when incised) and foreign debris. Preserve tissue of questionable viability; reassess in 24-48 hours.

Tissue Viability Assessment: Viable tissue is pink/red and bleeds when incised. Nonviable tissue is blue-black, leathery, or white and fails to bleed. When uncertain, use conservative debridement and reassess.

Suture Materials and Techniques for Bovine Skin

Suture Material Selection

Cattle have notably thick skin compared to other domestic species. This requires larger gauge suture material and cutting needles for skin closure.

Suture Patterns for Bovine Skin

Special Wound Considerations in Cattle

Teat Lacerations

Clinical Significance: Teat lacerations are emergencies that require immediate attention. Delayed repair (greater than 48-72 hours) increases fistula formation risk 8.3-fold compared to repair within 24 hours.

Closure Technique: Three-layer closure provides best outcomes: (1) Mucosa with 4-0 to 5-0 absorbable suture in simple continuous (must be "milk-tight"); (2) Submucosa with 4-0 to 5-0 absorbable simple continuous; (3) Skin with 2-0 to 3-0 non-absorbable simple interrupted.

Preferred Suture Material: Polydioxanone (PDS) is the best choice for teat repairs because it maintains tensile strength longer than other absorbables when exposed to milk.

Post-operative Care: Machine milk immediately (gentler than hand milking); avoid manual stripping for 2 weeks. Consider teat cannula if swelling prevents machine milking.

Synovial Structure Wounds

Wounds involving joints or tendon sheaths are emergencies requiring immediate exploration and lavage. Aspirate or inject the structure with 2% lidocaine to assess communication with the wound. Copious lavage (several liters) is essential. These wounds have poor prognosis if treatment is delayed or inadequate.

Wound Complications

Wound Infection

Clinical Signs: Increased pain, heat, swelling, and redness; purulent discharge; delayed healing; fever; malodor. Unhealthy granulation tissue appears dark red and bleeds easily on contact.

Common Pathogens: Staphylococcus aureus, Streptococcus species, Pseudomonas aeruginosa, Fusobacterium necrophorum, Arcanobacterium pyogenes (now Trueperella pyogenes).

Management: Culture and sensitivity testing if severe; debridement; copious lavage; systemic antibiotics; open wound management until infection controlled.

Clostridial Wound Infections

Sawhorse stance

Trismus (lockjaw)

Increased response to stimuli

Flared nostrils

Flying third eyelid (prolapse)

Tail elevated, ears erect, bloat common

Myiasis (Screwworm Infestation)

Cochliomyia hominivorax (New World screwworm) larvae can infest wounds, causing extensive tissue destruction. Treatment involves removal of maggots, debridement of affected tissue, topical insecticides/larvicides, systemic antibiotics for secondary infection, and fly repellents. Prevention through prompt wound treatment and fly control is essential.

Antimicrobial Therapy for Wound Infections