Effects of different winter paddock management of Thoroughbred weanlings and yearlings in the cold region of Japan on physiological function, endocrine function and growth.

This study focuses on the impact of different winter paddock management strategies on the physiological function, endocrine function and growth of Thoroughbred weanlings and yearlings in Hokkaido, Japan. It reveals the effectiveness of the limited outdoor exposure plus walking exercise in promoting growth and maintaining metabolism during the winter season.

Comparative Study on Different Paddock Management Practices

• The research involved two distinct management practices applied on Thoroughbred weanlings and yearlings in Hokkaido, Japan. This region endemic to extremely cold winters hence requires unique management practices to cater to these horses.
• The horses were divided into two groups – those that stayed outdoors for 22 hours (22hr group) and those that stayed outdoors for just seven hours but had one hour of walking exercise (7hr+W group).
• The comparison covered various factors such as daily distance traveled, body temperature (BT), heart rate (HR), HR variability (HRV), and changes in endocrine function and growth parameters between November of their birth year to January of the following year.

Observations and Findings

• The research noted that the 7hr+W group covered nearly the same distance as the 22hr group by using the horse-walker, indicating that the application of the horse-walker compensated for the reduced hours of outdoor exposure.
• By January, the 22hr group displayed a lower increase rate in body weight compared to the 7hr+W group. They also exhibited a decrease in body temperature and heart rate.
• The HRV analysis pointed out an increase in high-frequency power spectral density in the 22hr group, signaling a predominance of the parasympathetic nervous activity.
• Despite the cold environment, no significant changes in circulating cortisol and thyroxine were observed in the 22hr group. However, these hormones were increased in the 7hr+W group, along with prolactin and insulin-like growth factor.

Conclusion

• Through the derived physiological and endocrinological data, the study concluded that the less exposure plus exercise regimen (7hr+W) is more effective in stimulating growth and sustaining metabolism during the harsh winter season, as compared to prolonged outdoor exposure (22hr group).
• This finding provides pivotal insights into the preferable winter management practices for Thoroughbred weanlings and yearlings in extremely cold climates, potentially impacting horse rearing and racing industries significantly.