We are starting to experience the transition from winter to spring weather, but until temperatures are more consistent, we must take precautions with our horses. We’ll need to consider similar cautions during other seasonal transitions to ensure their digestive tract health.
One concern with dramatic diet changes is how they affect the healthy microbial population in the equine digestive tract, also known as the gut microbiome. This collection of microbes is necessary for proper breakdown of feedstuffs, in particular the more fibrous parts of the diet. Drastic changes in the diet can have a negative effect on the microbes, leading to issues such as colic and laminitis. Although commonly associated with a change in the concentrate portion of the diet, seasonal changes to pasture, especially increases in nonstructural carbohydrate levels, can have a similar effect.
Seasonal transitions are more concerning with horses that have been kept off pasture for a length of time, such as those kept on dry-lots/sacrifice lots during the winter to prevent damage to pastures. Horses that have been off pasture should be introduced to the available fresh forage gradually. One way to do this would be to limit the length of time the horse is on the pasture and gradually increase time allowed. Another option is to make the horse wear a grazing muzzle initially. Horses that have been on pasture continually undergo a natural transition and will usually have fewer issues with seasonal changes.
Probably the biggest concern with the transition from winter to spring is when the daytime temperatures are warm and nighttime temperatures are at or below freezing. This combination can cause plants to grow rapidly and accumulate excessively high levels of nonstructural carbohydrates, which can trigger a bout of colic or laminitis. These elevated nonstructural carbohydrates are also problems for horses with insulin dysregulation or equine metabolic syndrome, and horses might need to be moved from these fields temporarily until carbohydrate levels decrease. Another issue, although less common, is diarrhea or loose stool caused by spring forages’ high water content, especially after warm temperatures and rainfall. This is usually a temporary issue but should be monitored in case it persists.
Transitions from fall to winter might also have some of the same types of weather as observed in spring. Warm temperatures during the day with dramatic drops at night will cause the same lush growth and elevated nonstructural carbohydrate issues as observed in the spring. Another concern in winter months is making sure horses consume enough water. As the total diet transitions to more dry components, such as hay, we must ensure fresh water is available and at an appropriate temperature and that horses are staying hydrated. Horses that are not consuming adequate water can be prone to impaction colic.
Overall, owners must be aware of changes in the weather and prepare for them accordingly. Horses kept at pasture year-round tend to have fewer issues than horses removed from pasture for a period. Know your horse and watch for potential issues as the seasons change.