By Don Ball
There are lots of horses in Alabama and throughout the Deep South, ranging from pleasure horses to show horses. The value (economic and otherwise) of these animals, as well as their diets, varies greatly. Regardless, many horses have access to pasture during at least part of the year and are fed hay throughout most of the year. Despite the importance of forage in the diets of horses, relatively few forage research studies are conducted involving horses.
An exception is a study conducted at Texas A&M Commerce by Lauren Foster and Dr. Pat Bagley reported at the 2006 American Forage and Grassland Council Annual Conference in San Antonio, TX. (It may be of interest to some readers that Dr. Bagley was recently named Dean of Agriculture at Tennessee Tech University). I believe it is worth discussing this work because it addresses some issues on the minds of many horse producers these days. Furthermore, the results also should be of interest to cattlemen and other livestock producers as the findings have implications for them as well.
There were three objectives in this study. The first was to determine whether horses preferred Tifton 85 bermudagrass over Coastal and common bermudagrass (despite producing large stems, Tifton 85 has been widely reported to have higher digestibility than other bermudagrasses). The second was to determine whether the time of day during which hay is harvested affects preference by horses (this is another issue that has gotten quite a lot of attention in recent years). The third was to determine the dry matter digestibility of hay in both a.m.-cut and p.m.-cut hays of each bermudagrass type.
The approach used was to establish the three bermudagrasses in separate but nearby areas from which hay was subsequently cut in either morning or afternoon. At different times, hay of each of the three bermudagrasses was provided to individually-stalled horses. On a given day, the animals were given access to equal weights of both a.m.-cut and p.m.-cut hay of one of the bermudagrass types. After four hours of a horse having the ability to choose between the hay harvested in morning or afternoon, the amount of hay of each type remaining was weighed, thus providing evidence of preference. Also, by comparing results overall, the amount of hay horses consumed of various bermudagrass types could be compared as well. In addition, laboratory analysis and in vivo (rumen cannula digestion of hays) were determined.
This study showed on average the p.m.-cut hays were preferred over a.m.-cut hays, especially in the case of Tifton 85 and Coastal, which is consistent with other research done in recent years. It is believed the reason p.m.-cut forage is preferred is because they have a higher sugar content due to photosynthesis occurring during the daylight hours (as opposed to night when there is no photosynthesis and
free sugars tend to be used up by plant respiration). There was also a trend toward fiber (both acid-detergent-fiber and neutral-detergent-fiber) levels to be lower
for p.m.-cut hays.
It also showed a higher percent digestibility for Tifton 85 hay as compared to Coastal or common bermudagrass, as has been previously reported. (Interestingly, the forage quality of Coastal and common are similar; the advantage of Coastal is primarily a higher yield potential.) Digestibility and preference are usually highly correlated, but despite its higher digestibility, Tifton 85 forage is not necessarily preferred by horses. The finding that p.m.-cut hay is preferred by horses could be of importance in some situations, like where a good level of hay consumption is perceived to be particularly important (i.e. when horses have been under stress or are ill).
Don Ball is an Extension Forage Crop Agronomist with Auburn University.