What's in your bale of alfalfa?
By Kylene Scott
When hay supplies are tight and drought conditions in many areas limit current alfalfa production, buyers and sellers need to be as proactive as they can when finding quality alfalfa to feed to their livestock. Testing is one way to see exactly what is in the hay.
High-quality forages are crucial for livestock, furnishing essential energy, proteins, vitamins, minerals and fiber. Most domestic livestock depend almost entirely on forages as part of their diets. The best measure of forage quality is animal productivity, and in turn it is affected by forage intake, digestibility and nutrient utilization efficiency.
Vanessa Corriher-Olson, assistant professor and Extension forage specialist with Texas A&M University, recommends for feeding value, hay/forage needs to be analyzed for crude protein and energy. However, the TAMU Soil, Water and Forage Testing Laboratory provides crude protein, Acid Detergent Fiber, Neutral Detergent Fiber, nitrates and minerals as choices for testing.
“Most labs use chemical testing, but if producers want to know specifically in regards to the laboratory they use I would recommend asking the laboratory,” Corriher-Olson said. “Testing should be close to 100 percent accurate. If a producer ever has questions about an analysis they can visit with the laboratory and potentially have a sample run more than once.”
Daren Redfearn, associate professor, forage and pasture management at Oklahoma State University said two methods are often used to estimate forage nutritive value. They include direct chemical analyses and near-infrared reflectance spectroscopy, or NIRS.
“Forage analyses using NIRS are becoming popular due to the very short turn-around times,” Redfearn said. “When properly calibrated, NIRS results are highly correlated to direct chemical measurements. When in doubt, chemical measurements are most accurate.”
As far as buyers and sellers go, accuracy is key.
“It is extremely important,” Redfearn said. “However, probably more important is for both the buyers and sellers to understand that there can be normal variation between labs analyzing the same lot.”
Besides laboratory analysis, measuring animal performance is also a good indicator of whether hay is adequately meeting needs, Corriher-Olson said.
“If you overestimate the nutritive value of the hay, cattle will calve in poor condition and take longer to breed again. In the case of horses, low-quality hay is primary cause of impaction colic,” she said. “If you underestimate the hay’s nutritive value you may end up buying expensive supplements that are unnecessary. Timely forage analysis can prevent either of these costly scenarios.”
Redfearn said that relative feed value, or RFV, is an important measurement for alfalfa and is widely accepted—especially when marketing the crop.
“From a nutritional standpoint, crude protein is the most important,” he said. “The three most common forage analyses are total nitrogen (N), neutral detergent fiber (NDF), and acid detergent fiber (ADF).”
According to an OSU Fact Sheet PSS-2117 (Forage Quality Interpretations), RFV does not say anything about protein concentration or physical characteristics. Those traits must be evaluated along with the RFV for a complete assessment of forage quality.
Laboratories use slightly different formulas to calculate DDM and DMI, but final estimated values are similar. RFV has no specific nutritional meaning and is used only as an index of the relative value of a forage. It combines into a single number of the digestibility of the forage and an estimate of how much forage will be consumed. As maturity advances, crude protein and RFV generally decrease, and ADF and NDF increase. The RFV of alfalfa hay harvested at full bloom is expected to be about 100. The higher the RFV value, the higher quality of the forage.
Corriher-Olson said the TAMU Soil, Water and Forage Testing Laboratory use the following procedures: Plant nitrogen (or protein) is determined by a high temperature combustion process and is reported on a dry plant basis only. Nitrate (NO3-N) is extracted from plant samples using a 1 N KCl solution. Nitrate is determined by reduction of nitrate (NO3-N) to nitrite (NO3-N) using a cadmium column followed by spectrophotometric measurement. Fiber (ADF, NDF) is determined gravimetrically following a liquid digestion.
When collecting a sample for forage testing, there is a method to the madness. These two fact sheets from OSU and TAMU both have good recommendations for sampling procedures: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2553/PSS-2589web.pdf and http://publications.tamu.edu/FORAGE/PUB_forage_Sampling%20Hay%20Bales%20and%20Pastures%20for%20Forage%20Analysis.pdf.
Redfearn said special care needs to be taken when collecting samples.
“The most important consideration is taking a representative sample of the forage lot to be tested. Using a forage probe is preferable to grab sampling,” he said. “Forage sampling is the most critical factor for obtaining accurate forage testing results. There are different approaches for proper sampling of standing forage, small square bales, large square bales, large round bales, loose hay stacks, and cubes or pellets.”
Corriher-Olson agrees and said to obtain one composite sample for each lot of hay by taking sub-samples from at least 10 percent of each lot’s bales.
“This composite sample will represent the nutritive value for that lot of hay,” she said. “The ends and outer edges of bales are often weathered and decayed (especially if stored outdoors), so taking samples from these areas can understate the true nutritive value of the hay.”
Ideally, a hay probe, which removes a 1-inch diameter core, is the best way to gather a sample. It should be taken toward the center, midway up the side of the bale, Corriher-Olson said.
“Sampling near ends or bottoms of bales will not give you a representative sample,” she said. “Remove the outer 1/2 inch of the bale surface so the sample will not be contaminated with dust or debris. Then drill or core 12 to 18 inches into the bale and carefully put the sample into a paper sack.”
Repeat this procedure on several other bales from the same field and harvest date. Mix the subsamples thoroughly and submit the composite sample to the laboratory along with the laboratory submittal form.
“You should collect one composite sample for every 25 to 30 bales from a given field and cutting,” she said. “For every large lot of hay you should sample at least 10 percent of the baled hay. On square bales, take sample cores from the ends of bales toward the center. Collect one composite sample for every 400 square bales from a given field and cutting.”
Redfearn said some guidelines are to take a minimum of 20 average looking square bales, 10 representative bales when sampling either large squares or large round bales.
Factors affecting quality
Elements like soil moisture and fertility while alfalfa is growing can affect the quality, but generally the better the growing conditions, the higher the forage quality. According to Redfearn, with good growing conditions the most important factor affecting forage quality is stage of growth at harvest. With good growing conditions, the most important factor affecting forage quality is stage of growth at harvest, but quality can also be reduced during storage.
“Hay that is stored outside can lose significant dry matter and nutritive value,” Corriher-Olson said. “Typically, hay bales stored outside for several months develop at least 5 to 6 inches of outer surface that has no feed value and that animals will refuse.”
As for maturity stage, fields cut in the pre-bud stage have the highest leaf to stem ratio and produce the highest quality hay. This is because leaves are more digestible and higher in protein than stems.
“Fields cut in the pre-bud stage have the highest leaf-to-stem ratio and produce the highest quality hay,” Corriher-Olson said. “As plants mature, the stems become larger, lower leaves often fall from the plant and the leaf to stem ratio decreases, resulting in a decline of digestible protein and an increase in fiber.”
Leafiness is also important because 65 percent to 75 percent of the protein and digestible nutrients is found in the leaves. It is the most important observable quality factor. Alfalfa leaves, on the average, contain about 25 percent to 30 percent protein, while the stems contain only about 12 percent when harvested at the 1/10 stage of maturity. Leaf shatter also occurs during raking and baling.
“Loss of leaves during harvest results in reduced quality and yield,” she said.
Foreign matter in the hay—weeds, straw, old hay stubble, rocks and other materials—can cause issues with the livestock and have little or no feed value.
“Weeds are the most common type of contaminant,” Corriher-Olson said. “Hay quality is lowered as the foreign matter content increases.”
Kylene Scott can be reached by phone at 620-227-1804 or by email at firstname.lastname@example.org.
To retain the nutritious value of alfalfa, consider the following harvest suggestions:
Harvest at the proper growth stage: 1/10 bloom in spring and fall; pre-bud in mid-summer.
Do not rake and bale when the hay is too dry. The leaves of alfalfa are attached to the stem at a single point the petiole. When the hay is too dry, the petiole and leaves become very brittle. Turning, raking or baling hay at that time will cause serious leaf shatter. Do not rake excessively to decrease the drying time. The less that alfalfa is moved after cutting, the better.
Do not make the windrows too small and tight. Air is unable to move in and out and poor drying results.
Set conditioner rollers properly to crush the stems, otherwise the windrow is not uniform.
Increase drying time to prevent wet “slugs” from being baled.
Avoid cutting alfalfa when the ground is wet. This increases drying time and the chance of moldy hay.