By Dr. Harold Willis
Of course, the most important measure of food quality is how your animals respond and what your expenses and income are—not only the animals’ production of food or fiber, but also their health and reproductive success. Thus, the total advantage of high-quality alfalfa goes beyond that indicated by digestible nutrient content and is compounded by a potential for being consumed at higher levels, a faster rate of digestibility, and perhaps a more efficient conversion of digested energy to produce energy.
But how can you measure quality while the crop is growing without sending in samples for an expensive and hard-to-interpret lab test? One very simple and inexpensive method being used by a growing number of farmers is a refractometer, an optical instrument that measures percent sugars in the sap of a plant, which is correlated with the plant’s food-producing efficiency (photosynthesis) and with ultimate food quality. Refractometers are routinely used in the food industry, by canneries, wineries, and breweries for example, to measure the quality of the fruits and vegetables they buy from farmers or of the foods and drinks they manufacture.
Using a refractometer to check the quality of your crops is easy. Simply squeeze a few drops of juice from the stems or leaves of the plants onto the glass prism of the refractometer, close the “lid,” and look through the eyepiece. The sugar content is read on a numbered scale in units called Brix (same as percent). By comparing with standard levels (see table) or past readings that you have made, you can see how your crops measure up that day.
Because of the difficulty in measuring feed usability and protein quality, there may not be a correlation between refractometer sugar readings and protein test figures from a feed analysis lab. Not all “high protein” feeds are truly nutritious for your animals. The best indicator to go by is the refractometer reading. A feed with a high protein figure but a low sugar reading will not be of high quality for your animals. It would be better to have a lower protein figure and high sugar.
Source: How to Grow Great Alfalfa