Reduced-size microchips for identification of horses: response to implantation and readability during a six-month period.

The study focuses on the use of reduced-size microchips for the identification and tracking of horses, studying their readability and the physiological response of the animals after implantation. The results indicate that smaller microchips are as reliable as larger ones, can be implanted with minimal stress to the horse, and are accurately readable across a sustained period.

Microchip Implantation Process

• The study involved adult mares numbering 40, each of whom received an implanted reduced-size microchip (10.9×1.6 mm) on the left side of their necks. The size of conventional chips is usually 11.4×2.2 mm.
• These implanted microchips were then identified using three different scanners (A, B, C), immediately after implantation, and then again after 6, 12 and 28 weeks.
• A subset of 12 mares were subjected to both microchip implantation and control treatments. This was to determine physiological markers like cortisol, heart rate, and heart rate variability (HRV).

Readability of Microchips

• From the chip-bearing side of the neck, successful identification was achieved with all three scanners in all horses at all times.
• On the opposite side, Scanner C always managed to produce a 100% correct reading. For scanners A and B, the correct reading rate fluctuated between 60 and 100%.
• The reduction in size of the microchips did not impair readability, making them a viable option for horse identification.

Physiological Response to Implantation

• Following the implantation of the microchip and control treatment, both heart rate and the standard deviation of beat-to-beat intervals in HRV increased slightly, suggesting a minor physiological response.
• However, the cortisol concentration in the mares did not increase, indicating that implantation of the microchip does not cause notable stress in horses.

Conclusion

• The study concluded that reduced-size microchips are both highly reliable and practical for the identification of horses. Their reduced size does not interfere with their readability and does not cause pronounced stress to the animals. This means they could effectively replace conventional larger microchips in this context.