Abstract: Laser therapy is a non-invasive physical treatment technique based on photobiomodulation effects. It achieves therapeutic goals through light energy absorption and cellular metabolic regulation, improvement of blood circulation and increased oxygen supply, modulation of inflammatory responses and enhancement of immune function, pain relief and neural function regulation, and promotion of tissue repair and regeneration. It demonstrates significant efficacy in equine musculoskeletal diseases, endocrine system disorders, skin wound healing, ocular diseases, and other conditions. This article systematically reviews the biological mechanisms and clinical applications of equine laser therapy, aiming to provide scientific evidence-based medical support for equine laser therapy and promote the development of laser treatment technology.

Keywords: equine laser therapy; photobiomodulation effect; biological effects; clinical application

Author: Lu Wenyuan¹, Ma Yuhui², Zhang Yukun³, Qiu Zongsheng³, Ma Tianwen²,³*

(1. Zhaosu County Agriculture and Rural Affairs Bureau, Zhaosu, Xinjiang 835600, China; 2. Zhaosu County Xiyu Horse Industry Co., Ltd., Zhaosu, Xinjiang 835600, China; 3. College of Veterinary Medicine, Northeast Agricultural University; Heilongjiang Key Laboratory of Animal Disease Pathogenesis and Comparative Medicine, Harbin, Heilongjiang 150000, China)

Laser therapy is a non-invasive physical treatment technique with photobiomodulation effects as its core mechanism. Through the absorption of laser energy of specific wavelengths by tissue cells, it regulates cellular function via multiple pathways to achieve therapeutic objectives. Laser therapy is classified based on power or energy density into high-intensity laser therapy (HILT) and low-level laser treatment (LLLT). In surgery, HILT primarily exerts thermal damage and tissue ablation effects, while LLLT achieves non-invasive repair and anti-inflammatory regulation through photobiomodulation. As a physical treatment modality with considerable development potential in veterinary medicine, this technology is increasingly widely applied in equine disease treatment. It not only effectively shortens treatment cycles and reduces complication rates but can also synergize with drug therapy, platelet-rich plasma therapy, and other treatments to enhance efficacy while minimizing impact on normal tissues. Horses recover quickly after treatment without affecting normal activities.

1 Biological Effects

1.1 Light Energy Absorption and Cellular Metabolic Regulation

Laser energy is primarily absorbed by intracellular mitochondria, activating cytochrome c oxidase, promoting ATP synthesis, and enhancing cellular metabolic activity. Studies have found that infrared laser photons absorbed by the flavoprotein-metal redox system in the mitochondrial respiratory chain can increase ATP production by up to 150% [1]. Other studies have found that low-power lasers activate mitochondrial function through photochemical effects, while high-power lasers promote collagen remodeling through photothermal effects [2].

1.2 Improvement of Blood Circulation and Increased Oxygen Supply

Laser irraiation can dilate local microvessels, increase blood flow and oxygen delivery, and improve tissue hypoxia [3]. Zielińska et al. found that HILT could increase vascular diameter in the equine superficial digital flexor tendon region by 15%–20%, significantly improving local tissue perfusion [4]. Another study found that laser irradiation could improve skin microcirculation, increase surface temperature in the longissimus dorsi region of racehorses with back pain, and increase capillary density.

1.3 Anti-inflammatory Effects

Laser therapy can modulate the release of inflammatory mediators, inhibit the expression of pro-inflammatory factors, and promote the production of anti-inflammatory factors [5]. High-power laser therapy reduces local inflammatory responses through biostimulation and photomechanical stimulation, while simultaneously enhancing local microcirculation and promoting lymphatic drainage.

1.4 Pain Relief and Neural Function Regulation

Laser therapy achieves analgesic effects through multiple pathways, including inhibiting pain signal conduction and reducing nerve terminal excitability; promoting the release of analgesic substances such as endorphins and enkephalins; and improving the tissue microenvironment to reduce the accumulation of pain-inducing substances. Studies have found that HILT can reduce palpation pain scores in racehorses with back pain, reduce muscle spasms through photothermal analgesic effects, and relieve pain.

1.5 Tissue Repair and Regeneration

Laser irradiation can promote collagen synthesis and alignment, enhancing tissue strength. Low-level laser therapy can promote angiogenesis in hypoxic environments, increase type III collagen synthesis, and promote fibroblast proliferation. Additionally, lasers can promote epithelial cell migration, accelerate wound healing, and reduce scar formation.

2 Applications of Laser Therapy in Equine Diagnosis and Treatment

2.1 Musculoskeletal Diseases

Laser therapy is mainly used to treat tendonitis, ligament injuries, arthritis, back pain syndrome, and other diseases. Zielińska et al. conducted HILT treatment on 25 performance horses with superficial flexor tendonitis. Results showed that most horses could return to normal training, and ultrasound examination revealed significant improvement in tendon fiber alignment [4]. Research has confirmed that LLLT is suitable for early tissue repair in tendonitis, while HILT is more suitable for pain control and functional improvement; optimizing laser parameters can improve the therapeutic effect of tendon injuries. HILT promotes equine osteoarthritis cartilage regeneration and optimization of extracellular matrix composition through photoacoustic effects [2].

2.2 Endocrine System Diseases

Laser therapy has shown promising application prospects in the treatment of equine endocrine diseases. Petermann's study included 26 horses diagnosed with pituitary pars intermedia dysfunction (PPID). Laser therapy not only significantly alleviated typical clinical symptoms such as abnormal hair shedding and muscle atrophy but also normalized adrenocorticotropic hormone levels in affected horses. Some cases even regained riding ability [1].

2.3 Skin Wound Healing

Reports indicate that laser therapy is also applicable to acute trauma, chronic non-healing wounds, burns, and other conditions. Harman et al. used horses as a skin wound healing model and treated 2.5 × 2.5 cm² full-thickness wounds with 635 nm (17 mW/diode) laser, increasing the epithelialization rate by 30% and achieving complete healing in 80 days, providing experimental support for laser treatment of acute trauma and chronic non-healing wounds in horses [5].

2.4 Ocular Diseases

The application of laser therapy in equine ocular diseases includes corneal ulcers, uveitis, intraocular tumors, and others. Studies have shown that using low-power red light laser (300 mW, wavelength 660 nm) to irradiate periocular acupoints and conjunctival projection areas for 5–8 minutes per session, three times per week, can reduce conjunctival hyperemia, inhibit inflammatory exudation, and avoid drug stimulation to the cornea [3]. Ostendarp and Barton's discussion on the diagnosis and treatment of intraocular tumors in horses provided different perspectives and references for laser treatment of equine ocular diseases [6–7].

2.5 Other Diseases

In addition to the above diseases, laser therapy is also being explored for application in equine respiratory diseases, reproductive system diseases, and other fields [8–9].

3 Conclusion

Laser therapy, with photobiomodulation effects at its core, exerts therapeutic effects by regulating cellular metabolism, improving circulation and oxygen supply, inhibiting inflammation, providing analgesia, and promoting tissue repair. It plays an important role in the treatment of equine musculoskeletal, endocrine, skin, ocular, and other diseases. Future research needs to deepen the understanding of its mechanisms of action and further expand the application scenarios and value of laser therapy in equine disease treatment.

References

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[9] Zielińska P, Soroko-Dubrovina M, Śniegucka K, et al. Effects of high-intensity laser therapy (HILT) on skin surface temperature and vein diameter in healthy racehorses with clipped and non-clipped coat [J]. Animals, 2023, 13(2): 216.