Surgical Retractors and Exposure Techniques in Small Animals

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• Retraction is an active force-delivery process; optimal exposure balances visualization with tissue tolerance, achieved through intermittent, progressive application of force matched to tissue type.
• For abdominal midline celiotomy, the Balfour or Gosset self-retaining retractors are standard, while hand-held retractors (Deaver, malleable) are preferred for deep or dynamically changing fields, especially in obese patients where wound protectors offer superior circumferential exposure.
• Thoracic procedures, particularly lateral thoracotomy, necessitate gradual, deliberate opening of retractors like the Finochetto to mitigate rib fracture and neuropraxia, with instrumented retractors demonstrating significant reductions in mean and peak forces.
• Self-retaining retractors require periodic release (every 15-20 minutes) to prevent ischemia and tissue damage, a critical consideration for preventing pressure necrosis and incisional dehiscence.
• Traction sutures offer a valuable alternative for focal retraction, particularly in minimally invasive surgery or when an assistant is unavailable, providing stable, adjustable exposure without occupying surgical hands.
• Retractor-related complications, including neuropraxia (e.g., femoral nerve compression), visceral trauma (e.g., splenic capsular tears), and pressure necrosis, are preventable through systematic monitoring of tissue color, resistance, and periodic release of tension.

Exposure is the first act of every operation. A retractor is not a passive tool, it is a force-delivery device that determines what the surgeon can see, what the assistant can hold, and what the tissues will tolerate. This article addresses the selection and application of retractors for abdominal and thoracic procedures in dogs and cats, with emphasis on exposure principles and tissue handling. Orthopedic retractors are excluded. The intended reader is the practicing veterinarian who performs cellotomy, thoracotomy, or minimally invasive access and wants a structured framework for choosing between hand-held and self-retaining devices, managing retraction forces, and avoiding iatrogenic injury.

The clinical questions answered here are practical. Which retractor should be opened for a deep-chested dog with a splenic mass? When does a self-retaining retractor become safer than an assistant's hand? How does retraction technique differ between the abdomen and the thorax? The answers rest on biomechanical principles, comparative device design, and the limited but instructive experimental literature on retraction forces in large animal models.

At a Glance

Biomechanics of Retraction

Retraction transfers force from a handle or frame to the wound edge. The tissue response depends on the magnitude, direction, duration, and surface area of that force. A broad blade distributing load across a wide contact area produces less local pressure than a narrow rake at the same total force. This is the core distinction between atraumatic and traumatic retraction, and it governs blade selection for every layer of the body wall.

Experimental work in sheep has quantified what surgeons know intuitively. Instrumented retractors that display real-time force during median sternotomy allow the operator to achieve the same 7.5 cm exposure with a 37 percent reduction in mean force and a 31 percent reduction in peak force compared with unmonitored retraction at a standard clinical pace. The monitored retraction took longer, 12 minutes versus 7 minutes, but the force reduction was significant. Similar results were reported for lateral thoracotomy, where force feedback reduced mean force by 24 percent and peak force by 28 percent. These studies, reported in the instrumented retractor literature for median sternotomy and the instrumented retractor literature for lateral thoracotomy, establish that the pace of opening is a controllable variable with measurable tissue consequences.

The clinical translation is direct. Slow, incremental opening of any self-retaining retractor allows viscoelastic creep in the body wall, reducing the force required to reach a given width. Rapid opening spikes peak force, and peak force, not mean force, is the variable most associated with tissue disruption. For the thoracic cage, this means rib fracture, intercostal neurovascular injury, and postoperative pain. For the abdominal wall, it means muscle tearing at the blade tips and serosal abrasion of underlying viscera.

Hand-Held Retractors

Hand-held retractors remain the most versatile instruments in the small animal surgeon's set. Their advantages are tactile feedback, infinite angle adjustment, and the ability to change position continuously as the procedure evolves. Their disadvantages are fatigue, tremor, and the requirement that one hand of an assistant be occupied for the duration of the exposure.

The standard set should include a range of blade widths and depths. Army-Navy retractors suit superficial layers and small incisions. Senn and rake retractors provide secure purchase on subcutaneous fat and muscle but concentrate force at the tines. Deaver and malleable retractors are the workhorses for deep abdominal exposure, with the malleable blade bent to conform to the liver, spleen, or kidney. The choice between a Deaver and a malleable is often one of rigidity, the Deaver holds a fixed curve, while the malleable can be shaped to the individual patient's anatomy.

Hand-held retraction is preferred when the field is deep and the angle changes frequently, such as during dissection of the biliary tree or the adrenal gland. It is also preferred when the surgeon needs to vary retraction dynamically, releasing tension periodically to check perfusion or to allow the assistant to suction. The cost is that a good assistant is as important as a good retractor. An assistant who understands the plane of dissection and anticipates the surgeon's next move will hold tension where it is needed, not where the instrument happens to rest.

Self-Retaining Retractors

Self-retaining retractors free the assistant's hands and provide steady, reproducible exposure. The Balfour retractor, with its lateral blades and optional third blade for cranial or caudal retraction, is the standard for midline cellotomy in dogs. The Gosset retractor, a ring-based design, offers a lower profile and is useful in smaller patients or when the surgical field is crowded. Both rely on a ratchet mechanism that locks the blades at a fixed separation.

The principal risk of self-retaining retraction is that the locked position becomes a static force. Tissues under constant tension develop ischemia, and the blade edges can crush muscle or bowel if left in place too long. The remedy is periodic release. Many surgeons loosen the ratchet every 15 to 20 minutes, allow the wound to relax, and then re-expand to the same width. This simple maneuver interrupts the ischemic period without sacrificing exposure.

Blade selection matters as much as frame selection. Deep, narrow blades are appropriate for the cranial abdomen where the diaphragm and liver limit lateral excursion. Wide, shallow blades suit the mid-abdomen where the body wall is more compliant. The Balfour's third blade, positioned cranially or caudally, is often the difference between adequate and excellent exposure of the spleen or the bladder.

Wound Protectors as Exposure Devices

Disposable wound protectors, long used in human surgery, deserve attention in small animal practice. These devices consist of a flexible ring that is inserted through the incision and a second ring that remains external, with a plastic sheath connecting the two. The external ring can be rolled down to retract the wound edge circumferentially, distributing force evenly around the entire incision instead of at discrete blade points.

Comparative data from an animal tissue model show that wound protectors can outperform a self-retaining retractor for a given incision length. In that study, the wound protector exposure comparison in open hernia repair demonstrated statistically significant increases in exposed surface area for incisions of 3 to 6 cm when using a small wound protector versus a Mollison self-retainer. The effect was largest at longer incisions, where the wound protector achieved roughly double the exposed area of the self-retainer.

The mechanism is geometric. A self-retaining retractor pulls the wound edges laterally, creating a roughly elliptical opening. A wound protector rolls the full thickness of the body wall outward, converting the incision into a circular aperture with a larger effective area. The wound protector also shields the wound edges from contamination and from desiccation, a secondary benefit that is difficult to quantify but clinically relevant. For small animal surgeons performing ovariectomy, cystotomy, or intestinal resection through incisions of 3 to 6 cm, the wound protector is a legitimate alternative to the Balfour, particularly when an assistant is unavailable.

Retraction in Minimally Invasive Access

Minimally invasive surgery changes the retraction problem. The abdominal wall is not retracted laterally but elevated, either by gas insufflation or by mechanical lift. Gasless laparoscopy, described in early case series of vascular procedures, used a mechanical arm to elevate the abdominal wall and fan retractors to maintain exposure of the operative field. The gasless laparoscopic exposure technique demonstrated that conventional instruments and open retraction principles could be adapted to a closed cavity, though the approach required multiple ports and careful attention to maintaining the working space.

For the veterinary laparoscopist, the relevant lesson is that retraction within a closed cavity is a matter of positioning, not force. Fan retractors and atraumatic grasping forceps hold viscera away from the target organ, but the pressure they exert is transmitted through the body wall and can cause bruising if applied carelessly. The same principle of broad contact area applies: a fan retractor with widely spaced tines distributes force better than a narrow grasper.

Traction sutures offer another retraction strategy that avoids instruments entirely. The self-stabilizing interdental traction suture technique, described for palatal flap retraction in human oral surgery, uses sutures passed through adjacent structures to hold tissue without manual or mechanical retraction. The principle transfers to veterinary surgery wherever a flap or organ edge can be secured to a fixed point. A stay suture placed through the body wall or a rib can retract the liver, spleen, or lung lobe without occupying an assistant's hand. The technique is simple, reproducible, and particularly valuable in single-surgeon procedures.

Abdominal Exposure: Practical Selection

The choice of retraction system for abdominal surgery depends on incision length, patient body condition, target organ, and the surgeon's preferred hand position. For a standard midline celiotomy in a 10 to 20 kg dog, a Balfour retractor with medium blades provides reliable lateral wall retraction and maintains exposure of the mid-abdomen. In cats and small dogs under 5 kg, a Gelpi retractor placed at the cranial and caudal ends of the incision often suffices, though the sharp points require careful placement to avoid tearing the thin external rectus sheath.

For procedures requiring deep pelvic or cranial abdominal exposure, the Balfour's fixed blades may not reach. A Gosset retractor, which has a lower profile and curved blades, fits better in the caudal abdomen of deep-chested breeds. When the target is the liver or diaphragm, a Finochetto retractor with long, narrow blades and a ratchet mechanism allows gradual, sustained elevation of the costal arch without the fulcrum effect of a hand-held retractor.

Patient body condition changes the decision. In obese patients, the subcutaneous fat layer collapses into the incision and obscures the linea alba. A wound protector, instead of a self-retaining retractor, holds fat aside and distributes pressure evenly along the full incision circumference. In a porcine tissue model, disposable wound protectors produced significantly larger exposed surface areas than a self-retaining retractor for incisions of 4 cm and longer, with the difference increasing as incision length grew wound protector exposure study. For a 6 cm incision, the protector exposed nearly twice the surface area of the self-retainer. This advantage is most pronounced in thick-walled abdomens where conventional blades bury into fat instead of retract it.

The table below summarizes selection criteria for common abdominal approaches.

Thoracic Exposure and Force Management

Lateral thoracotomy and median sternotomy both require retractors that can generate substantial force to spread the thoracic wall. The force needed to achieve a given exposure varies with patient size, chest conformation, and the pace of retraction. Instrumented retractors used experimentally in sheep demonstrated that retraction to 7.5 cm at a standard clinical pace produced average forces near 103 N, while retraction with real-time force feedback and a slower, deliberate pace reduced average force by 24% and peak force by 28% instrumented thoracotomy retractor force study. A similar sternotomy study found a 37% reduction in average force with feedback-guided retraction median sternotomy retraction force study.

The clinical translation is direct. Open the retractor gradually, in small increments, allowing the tissues to creep and relax between turns. Avoid the common habit of cranking the ratchet to full spread immediately after placement. In deep-chested dogs undergoing lateral thoracotomy, the Finochetto retractor should be positioned with the blades perpendicular to the ribs and the rack facing the surgeon. Place moistened laparotomy sponges between the blade tips and the lung or pericardium to prevent direct parenchymal trauma.

For median sternotomy, the Finochetto or a specialized sternal retractor spreads the two hemithoraces. The force is transmitted through the costochondral junctions and the sternal periosteum. Excessive or rapid force risks rib fracture at the costochondral junction, particularly in older cats with brittle bone. If resistance increases sharply during spreading, stop, check blade position, and reassess. The blades may have slipped off the sternal edge and be engaging intercostal muscle alone.

Atrial and Cardiac Exposure

Exposure of the mitral valve or other left-sided cardiac structures requires retraction of the atrial wall without obstructing the surgical field. In a porcine cadaver model, a novel minimally invasive atrial retractor achieved comparable access to the mitral valve annulus (92.7% versus 93.0% for a standard atrial retractor) while requiring significantly less time to place and providing subjectively more working volume within the atrium atrial retractor comparison study. Tissue damage occurred in one of five cases with the novel retractor and two of five with the standard device.

For open atrial approaches in small animals, the practical options are a hand-held malleable retractor held by an assistant or a self-retaining atrial retractor with soft, atraumatic blades. The left atrial wall is thin and tears easily. Retraction should be applied perpendicular to the atriotomy edge, with the blade tip positioned to avoid the atrioventricular groove and the circumflex coronary artery. Intermittent release of retraction every few minutes reduces ischemic injury to the atrial wall.

Traction Sutures as an Alternative

Traction sutures offer a low-cost, low-profile alternative to mechanical retractors in selected situations. A described technique for palatal flap retraction uses self-stabilizing interdental traction sutures passed through interdental embrasures and anchored against the contralateral arch self-stabilizing interdental traction suture technique. The technique eliminated the need for continuous manual retraction, prevented retractor slippage, and avoided flap tearing from uneven force distribution in a series of 10 patients.

The same principle applies in small animal surgery. Stay sutures placed through the edge of a body wall incision, a lung lobe, or a bladder wall can provide stable, adjustable retraction without occupying an assistant's hand. For celiotomy closure, stay sutures through the linea alba at the cranial and caudal incision ends allow the surgeon to elevate the body wall while placing the first closure sutures. For thoracic procedures, a stay suture through the pericardium or a lung lobe can provide exposure of the heart base without a retractor blade in the field.

Traction sutures are most useful when the exposure requirement is focal instead of diffuse, when the surgical field is small, and when an assistant is unavailable. They do not replace self-retaining retractors for wide, sustained exposure of the abdominal cavity.

Monitoring During Retraction

Retraction is not a static act. The surgeon should monitor tissue response continuously throughout the procedure. Pallor or duskiness of a retracted organ indicates vascular compromise. Capillary refill in the exposed mesentery or omentum should be assessed periodically. If a loop of intestine held by a retractor blade becomes pale, reposition the blade or interpose a moistened sponge.

Systemic signs of excessive retraction include hypotension and tachycardia, which may reflect vagal stimulation from mesenteric traction or pain from thoracic wall spreading. In the instrumented thoracotomy studies, heart rate and blood pressure were monitored throughout retraction, and force feedback did not significantly alter these parameters, suggesting that hemodynamic changes are not a reliable early indicator of excessive force instrumented thoracotomy retractor force study. Direct observation of tissue color and resistance to further spreading are more sensitive indicators.

Document the retractor type, blade size, and any complications such as serosal tearing or rib fracture in the surgical record. Note the duration of retraction and any repositioning performed. This documentation supports postoperative assessment of complications such as incisional pain or neuropathy and informs the choice of retraction strategy for future procedures on the same patient.

Complications and Failure Modes

Retractor-related injury typically presents in one of three patterns: neuropraxia, visceral trauma, or pressure necrosis. Early detection depends on systematic inspection at defined intervals instead of reliance on subjective feel.

Neurapraxia most often involves the femoral nerve during abdominal retraction and the radial or brachial plexus during thoracic retraction. Deep retractor blades placed with excessive cranial or caudal angulation compress nerves against the body wall. Detect by observing hindlimb extension or knuckling in the immediate postoperative period. The discriminating feature is motor dysfunction without signs of pain or swelling, which distinguishes neuropraxia from vascular compromise.

Visceral trauma includes splenic capsular tears from blade edges, hepatic contusion from overzealous liver retraction, and serosal abrasions that later form adhesions. Splenic injury is detected intraoperatively as progressive darkening of the capsule or free blood in the field. Hepatic trauma may be silent until reperfusion injury manifests as postoperative hypotension or prolonged recovery.

Pressure necrosis develops when a self-retaining retractor remains at maximal spread beyond 45 to 60 minutes. The abdominal wall becomes pale, then dusky, then frankly ischemic. Early detection requires lifting the retractor blades briefly every 20 to 30 minutes and observing capillary refill in the incised muscle edges. Delayed detection presents as incisional dehiscence or unexplained fever at 48 to 72 hours.

Common Errors and Corrective Action

The most frequent error in teaching settings is selecting a retractor that is too large for the patient. A blade that extends beyond the incision depth places pressure on structures the surgeon cannot see. Corrective action is to choose the smallest blade that exposes the target structure and to confirm blade position visually before engaging a self-retaining ratchet.

A second error is progressive over-tightening of self-retaining retractors. Each ratchet click increases force exponentially, and the surgeon who tightens "just one more click" to improve exposure is unknowingly increasing tissue disruption. Instrumented retractor studies in sheep demonstrate that force feedback reduces average retraction forces by 24 to 37 percent while maintaining equivalent exposure, and that slower, deliberate retraction produces lower peak forces than rapid spreading. The corrective habit is to spread the retractor in small increments, wait 30 seconds for tissue creep, and reassess before adding further tension.

A third error is failure to reposition the retractor as the procedure progresses. Tissues fatigue and stretch, and a blade that was correctly placed at the start of a splenectomy may migrate toward the pancreas or duodenum by the time ligation begins. Re-evaluate blade position at each major procedural step.

Students also commonly confuse exposure with force. When the field is inadequate, the instinct is to pull harder. The correct response is to reassess incision length, patient positioning, and whether a different retractor type would distribute force more effectively. Wound protectors, for example, provide statistically significant increases in exposed surface area compared with self-retaining retractors for incisions of 3 cm or longer, which means the solution to poor exposure may be a different device instead of more tension.

Evidence Limitations and Divergent Expert Opinion

The evidence base for retractor selection in small animal surgery is largely extrapolated from human and experimental large animal studies. Force data from instrumented sternotomy and thoracotomy retractors in sheep provide useful thresholds, but no equivalent data exist for dogs and cats of varying body condition. Expert opinion differs on acceptable retraction duration, with some surgeons advocating release every 20 minutes and others relying on visual assessment of tissue perfusion alone.

The clinical significance of measured force reductions remains uncertain. The ovine studies show that force feedback lowers measured forces, but they do not demonstrate a corresponding reduction in postoperative pain or complication rates. Whether the 24 to 37 percent force reduction translates into clinically meaningful outcome differences is unresolved.

Comparative data on wound protectors come from an animal tissue model instead of live surgery, and the exposure advantage may not translate directly to the compliant abdominal wall of a live patient. Similarly, novel atrial retractor designs show comparable mitral valve exposure to established devices in a porcine cadaver model, but cadaveric tissue does not replicate the bleeding, movement, and tissue compliance of the beating heart.

Referral and Escalation Criteria

Referral to a specialist surgeon is warranted when exposure cannot be achieved without excessive force, when a planned procedure requires retraction beyond the surgeon's routine experience, or when intraoperative complications such as splenic laceration or suspected nerve injury occur. Specialist consultation is also appropriate for minimally invasive approaches where the surgeon lacks dedicated instrumentation, since gasless laparoscopic techniques require mechanical arm systems and specialised fan retractors that are not standard in general practice.

Laboratory involvement is indicated when unexplained postoperative complications suggest a retractor-related injury that may have systemic effects, such as suspected rhabdomyolysis after prolonged thoracic retraction or coagulopathy following unrecognised hepatic trauma. Serial muscle enzyme measurement and coagulation panels are appropriate in these circumstances.

Regulatory reporting obligations vary by jurisdiction. Practitioners should consult their regional veterinary board or professional body for specific requirements regarding reportable surgical complications. The American Veterinary Medical Association practice resources and the World Organization for Animal Health terrestrial animal health standards provide general frameworks for professional accountability, though neither substitutes for local requirements.

Frequently Asked Questions

How do I choose between a hand-held and a self-retaining retractor for a given procedure?

Select based on the duration of retraction, the depth of the surgical field, and the need for dynamic repositioning. Hand-held retractors suit short phases where the assistant must adjust tension continuously, such as during intestinal resection and anastomosis. Self-retaining retractors free both hands and provide steady, even exposure for prolonged procedures like splenectomy or ovariohysterectomy in deep-chested dogs. For abdominal exploration, a self-retaining retractor with malleable blades offers consistent lateral traction while the surgeon palpates viscera. When the field is shallow, a hand-held retractor allows finer control of tissue tension. Consider that self-retaining retractors apply static force, which increases the risk of neuropraxia or muscle ischemia during long surgeries. Alternate blade positions or periodically release tension when the procedure permits.

What should I do when the ideal retractor is not available?

Improvise with instruments already in the pack. A malleable retractor bent to the required curve can replace a specialized deep retractor. Laparotomy sponges packed around viscera provide gentle, diffuse displacement and protect tissues from rigid blades. Traction sutures placed through the body wall or wound edges distribute force evenly and eliminate the need for a dedicated retractor, a technique described for palatal flap retraction that also applies to abdominal wall retraction in small patients self-stabilizing interdental traction sutures. Towel clamps attached to drapes can secure wound edges for short periods. If exposure remains inadequate, extend the incision instead of accept poor visibility. A longer incision with controlled retraction causes less tissue trauma than excessive force through a short incision. Document any improvised technique in the surgical record.

How does retractor selection differ between cats and dogs?

Patient size and body wall compliance drive the differences. Cats tolerate less static retraction force because their thinner body walls transmit force more directly to underlying viscera and neurovascular structures. Use smaller blades, shorter rake teeth, and lower tension settings on self-retaining retractors. A Gelpi retractor sized for cats should open no wider than necessary to expose the target organ. In dogs, the choice depends on body conformation instead of weight alone. Deep-chested breeds require longer blades to reach the diaphragm or cranial abdomen, while broad-chested dogs benefit from wider blades that distribute force over a larger surface area. In both species, check capillary refill and pulse quality in the limbs after prolonged thoracic retraction, as excessive spread can compress the brachial plexus or great vessels.

What information should I record about retractor use in the surgical report?

Record the type and size of each retractor used, the duration of retraction, and any complications such as serosal tearing, muscle bruising, or neuropraxia. Note the maximum blade spread for self-retaining retractors, particularly in thoracic procedures where force correlates with postoperative pain. If you used an improvised retraction method, describe it precisely so another surgeon can reproduce or improve upon it. Document any tissue damage attributed to retraction, even if minor, and the corrective action taken. This information supports postoperative monitoring and informs future surgical planning for the same patient. For referral cases, include retraction details in the discharge summary so the receiving clinician understands potential sources of postoperative discomfort. The American College of Veterinary Surgeons practice resources provide guidance on standard surgical documentation expectations.

How do I explain retractor-related complications to an owner?

Use concrete language that connects the complication to observable recovery. Explain that retractors hold tissues apart during surgery and that prolonged or forceful retraction can cause temporary bruising or nerve irritation. Reassure owners that most retraction-related injuries resolve without specific treatment, but describe the expected timeline. For example, a patient with forelimb neuropraxia after thoracotomy may show weakness for days to weeks. Frame the discussion around monitoring parameters: appetite, activity level, and willingness to use the affected limb. If the complication is permanent, which is rare, state this clearly and outline rehabilitation options. Direct owners to the MSD Veterinary Manual for general information about surgical recovery, but emphasize that their veterinarian's specific instructions take priority.

When should I refer a case because of exposure difficulties?

Refer when you cannot achieve adequate exposure without excessive force or unacceptable tissue trauma. Specific triggers include an inability to palpate or visualize a target organ, a mass that cannot be safely mobilized, or a patient whose body condition prevents safe retraction. Refer early if you anticipate needing specialized equipment such as an atrial retractor for mitral valve exposure, as described in porcine models where dedicated atrial retractors provide comparable access with faster placement than standard instruments evaluation of a novel atrial retractor. Also refer when a previous surgery has created adhesions that obscure normal planes. Before referral, stabilize the patient, close the incision in layers, and document the exposure limitations you encountered. Communicate directly with the receiving surgeon, including your retraction strategy and any tissue damage observed.

Related Clinical & Scientific Guides

• Perioperative Antibiotic Prophylaxis: Timing and Selection
• Surgical Approaches to the Femur and Stifle
• Fracture Healing Assessment: Radiographic and Clinical Evaluation

References and Further Reading

• Laparoscopic vascular surgery: four case reports.. 1995.
• Wound protectors for improved exposure in open hernia repair.. 2019.
• Evaluation of a novel atrial retractor for exposure of the mitral valve in a porcine model.. 2008.
• A novel instrumented retractor to monitor tissue-disruptive forces during lateral thoracotomy.. 2007.
• Tissue-disruptive forces during median sternotomy.. 2007.
• Self-stabilizing interdental traction sutures for palatal flap retraction during impacted maxillary canine exposure: a technical note.. 2026.
• American College of Veterinary Surgeons Animal Health Resources. American College of Veterinary Surgeons.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.

Related Articles

• Laparoscopy in Small Animal Surgery: Patient Selection and Techniques
• Surgical Biopsy Techniques: Incisional vs Excisional
• Surgical Approaches to the Abdomen: Cellotomy and Exposure
• Surgical Draping Materials and Techniques for Contamination Control
• Surgical Instrumentation: Essential Set and Handling Techniques

This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.