Forage analysis can be a useful tool to remove some of the mystery concerning the hay that producers will feed this winter. Testing the grass hays this year for protein and energy content will help the producer design winter supplementation programs most appropriate for the forage supply that is available. Any of the potential nitrate accumulating hays should be tested for nitrate concentration.
Forage quality has two important benefits to cows or heifers. First higher quality forages contain larger concentrations of important nutrients so animals consuming these forages should be more likely to meet their nutrient needs from the forages. Secondly, and just as important, animals can consume a larger quantity of higher quality forages. Higher quality forages are fermented more rapidly in the rumen leaving a void that the animal can fill with additional forage. Consequently, forage intake increases. For example, low quality forages (below about 6% crude protein) will be consumed at about 1.5% of body weight (on a dry matter basis) per day. Higher quality grass hays (above 8% crude protein) may be consumed at about 2.0% of body weight. Excellent forages, such as good alfalfa, silages, or green pasture may be consumed at the rate of 2.5% of body weight per day. The combination of increased nutrient content AND increased forage intake makes high quality forage very valuable to the animal and the producer.
The value of forage testing can best be illustrated by comparing the supplement needed to meet the nutrient needs of cows in the winter. Assume we are feeding hay to a 1200 pound spring-calving cow in late gestation. She needs 1.9 pounds of crude protein to meet her needs and that of the growing fetus. If she consumes 2.0% of her body weight in a low quality grass hay (4.0% Crude Protein) she will receive 0.96 pounds of protein from the hay leaving a deficiency of 0.94 pounds of protein needed from the supplement. To meet her protein needs with a 30% crude protein supplement would require 3.13 pounds of supplement each day. However, if the same cow was consuming a higher quality grass hay (7.0% Crude Protein), then she receives 1.68 pounds of protein from the hay and must be given enough supplement to meet the 0.22 pounds that is lacking. Now, to meet her needs the cow only needs 0.73 pounds of the same supplement per day. Because of the difference in hay quality the supplement needs vary by 4 fold!
There are several good methods of sampling hay for forage analysis. Most nutritionists would prefer to use a mechanical coring probe made specifically for this purpose. The coring probe is usually a stainless steel tube with a serrated, cutting edge. It is 1 inch in diameter and is designed to fit on a 1/2 inch drill or brace. Cordless drills make these tools quite mobile so that the hay bales to be tested do not have to be hauled to be near an electrical outlet. The hay samples are place in paper or plastic bags for transfer to a forage testing laboratory. Cores are taken from several bales at random to obtain a representative sample to be analyzed.
Grab samples can also be obtained and tested. To receive the best information, grab several samples by hand from about 6 inches into the open side of the bale or the middle third of a small round bale. Place all of the sample in the bag. Do not discard weeds or stems, just because they look undesirable. They are still part of the hay that you are offering to the livestock. Be certain to label the forage samples accurately and immediately, in order for the laboratory analysis to be correctly assigned to the proper hay piles or bales. Obviously the more samples that are sent to the laboratory for analysis, the more information can be gained. Just as obvious is the fact that as the number of samples increase, the cost of forage testing increases.
Samples can be taken to the OSU County Extension office near you and then sent to the OSU Soil, Water, and Forage Testing laboratory in Agricultural Hall on the campus at Stillwater. There are other commercial laboratories available in the Oklahoma City area that also do an excellent job of forage analysis.