With the onset of winter, farms must be more mindful than ever of the quality of the hay they feed to their horses.  The University of Kentucky College of Agriculture, in an article run in TheHorse, and with significant contributions from Laurie Lawrence, PhD, discusses what some consider one of the best possible ways to evaluate hay.  While many different types of analyses are available, a good number of the methods are primarily focused on nutrients and chemicals, while some managers just want to compare the dollar value, or get an overall nutritional assessment. 

Nutritionists have therefore developed equations to give more generalized estimates of the quality of forage—one such is known as the relative feed value (RFV).  Although the standard was developed for cattle, it can be used for any livestock.  In the process of the calculation of the value, two variables are calculated from the concentration of two different types of fiber—neutral detergent fiber (NDF) and acid detergent fiber (ADF):

• the digestibility of the hay
• the level of consumption of the hay

The assumption is that as the hay quality increases, so does the ease with which it can be digested, and the rate at which it can be consumed.  Furthermore, as the plant matures, it becomes more fibrous (read: stemmy)—a result of increased concentrations of both NDF and ADF.  As the fiber increases (read: hay ages), the RFV decreases.

Bottom-line: young, leafy hay has a higher RFV than mature, stemmy hay.

How does this transfer to calculating the value of a load of hay?  While there are no RFV formulas specific to horses, the approximate forage quality can still be estimated (levels of protein, calcium, phosphorus, or other nutrients are not measured in RFV).  A higher RFV is generally associated with a higher forage quality.

It is important to note that high RFV-value hay is might not be the best for every horse—depending on energy level, moderate or lower RFV-value hay may be better.  Also worth noting—the higher the RFV hay that is fed, the less concentrate that will need to be added—which can significantly lower feeding costs.

On a closing note, since the RFV is calculated from a laboratory sample, a visual inspection is still a necessary step pre-purchase—the lab does measure cleanliness.

The information above, as well as the table below comes from Article #19284, UK College of Ag—available at http://www.thehorse.com/ViewArticle.aspx?ID=19284.

- Dayn Johnson