Effects of season on placental, foetal and neonatal development in horses.

The research investigates the effects of seasonal changes on the development of foals in horses. The researchers found that foals born earlier in the year tend to be smaller due to the impact of winter months on the final growth phase.

Study Design and Groups

• The study divided mares and their foals into three groups based on the day of foaling within a year. Group 1 foaled from the 40th to 65th day of the year, Group 2 foaled from the 67th to 92nd day, and Group 3 from the 94th to 121st day.
• There was no difference in terms of the parity (number of times a mare has given birth) across these groups.

Data Collection

• For the foals, parameters such as height at withers and body weight were measured from day 1 to day 5 and then weekly until they reached 12 weeks of age.
• Other measurements taken included chest circumference, distance from the fetlock to carpus (forelimb joints), carpus to elbow, poll (part between the ears) to nose, and crown-rump length (from the top of the head to the base of the tail).
• These measurements were also taken on the 5th day and then weekly until the 12th week. Placental weight and surface were also measured.

Results of the Study

• The study found that placental weight and surface area were lower in Group 1 (those that gave birth earlier in the year) than in Groups 2 and 3.
• Foal weight and length measurements increased over the study period. The height at withers in Group 1 was consistently smaller than in Groups 2 and 3.
• Moreover, distances from the fetlock to carpus, carpus to elbow, and poll to nose were smaller in Group 1 than in the other two groups.
• However, there was no difference in foal weight between groups. Additionally, gestation length and sex ratio of foals were the same across all groups.

Conclusion

• The study concluded that the size of the fetus is reduced when the final growth phase occurs during winter months. This also impacts neonatal growth during the first three months of life, causing foals born earlier in the year to be smaller.