Forage testing-A key decision aide in 2011

Oct 14, 2011
by WLJ

Oklahoma producers find themselves out of their “comfort zone” as they go into the winter of 2011-2012. Many have marginal or inadequate forage supplies. However, others may find themselves with forage of unknown origin (because they justifiably felt the need to purchase whatever hay they could find) and therefore of unknown quality. In some cases, producers may cut and bale hay in the latter weeks of October, because the October rains have allowed re-growth of some warm season pastures. Late October or November certainly is not the ideal time to harvest warm season pastures, but when other hay is scarce, that regrowth is hard to turn down.

Some of this “late cutting” hay could be adequate in protein and energy content, while other fields may yield very low quality forage and need considerable supplementation to enhance the usefulness of the hay.

Perhaps the most frightening “unknown” about hay this year is the potential for nitrate accumulation in some hay crops. Johnsongrass, millets, forage sorghums, Sudan hybrids were heat and drought stressed across much of the southwest. Any of these plants when stressed can accumulate toxic levels of nitrate. Read more about this topic in Oklahoma State University (OSU) Fact Sheet PSS-2903, Nitrate Toxicity in Livestock, available online or at any OSU County Extension Office.

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. Second, 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 percent crude protein) will be consumed at about 1.5 percent of body weight (on a 100 percent dry matter basis) per day. Higher quality grass hays (above 8 percent crude protein) may be consumed at about 2 percent of body weight. Excellent forages, such as good alfalfa, silages, or green pasture may be consumed at the rate of 2.5 percent 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.

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. Read more about forage sampling in OSU Fact Sheet PSS-2589, Collecting Forage Samples for Analysis.

Producers who find moldy hay or have concerns about mycotoxins in forages should take hay samples to their local veterinarian. These samples then can be forwarded to the Oklahoma Animal Disease Diagnostic Laboratory in Stillwater for mycotoxin analysis and appropriate recommendations.

Glenn Selk, OSU Emeritus Extension Animal Scientist