Understanding Forage Production and Forage Quality
Steps to Successful Pasture Improvement
By John Hibma – Forages are the foundation of all livestock diets. The production and feeding of high-quality forages will help ensure that livestock grows at an optimal rate, produce food and fiber, and remain healthy without the addition of large amounts of supplemental feeds in their diets. High-quality forage production will deliver the maximum amount of nutrition in a given amount of a plant’s organic material. Forages are also an integral part of improving the structure of soil and the quality of pastures and hay fields.
The definition of forage quality as feed centers on how digestible it is when livestock eat it. For the most part, the more leaves and the fewer stems found in a forage, the more digestible it will be for an animal and the greater the level of nutrition it will deliver. The more mature a plant becomes while it’s growing (meaning if it has produced flowers or seeds), the more stem it must create to hold the plant upright. As a plant matures, the stem-to-leaf ratio increases which lowers the percentage of organic material that can be digested and used for nutrition.
High-quality forage production begins in the field or pasture. Whether a forage is a warm season or a cold season grass or a legume, the plants start off as mostly leaf as they photosynthesize sunlight for nutrition in the early vegetative stage. The leaf is high in protein and simple sugars, both of which are highly digestible in an animal’s digestive system. The plant’s cell-wall material, which is less digestible, makes up a smaller proportion of the plant in the early vegetative stage. As plants mature, sugars and proteins are converted into more complex molecules called cellulose that the digestive microbes in livestock stomachs have increasing difficulty fermenting and digesting.
Whether a farmer is growing grasses or legumes for hay or haylage or feeding livestock on pasture, the most nutritious forage will always be found in the early vegetative stage of the plant’s life before it has started flowering or gone to seed.
Livestock on pasture can be very choosy in what forages they prefer to eat. They will avoid the less palatable forages, leaving them to mature and propagate while they over-graze a more palatable and nutritious species. Knowing what is rotational grazing can be very beneficial to livestock. It can be an excellent way to manage and improve pastures to avoid over-grazing while keeping weeds and other unwanted plant species out. Farmers who are in business to make hay or haylage must learn the best time to mow and bale their forages to maximize tonnage and production while, at the same time, not sacrificing forage quality as the forage becomes too mature.
Understanding the analytic terminology to describe forage and forage testing can help livestock owners either in purchasing high-quality forages or in the production of high-quality forages in their pastures and hay fields. The two most relevant terms in evaluating forage quality are the Crude Protein (CP) and Neutral Detergent Fiber (NDF). Crude protein is a measure of the nitrogen and amino acids which are essential for proper skeletal and muscle growth and other metabolic functions. Inadequate protein in a diet will result in slow gains for young stock, poor milk production for cows and goats and poor fiber quality for sheep and llamas. Crude protein and NDF tend to be inversely proportional. As one goes up the other goes down.
Forage testing laboratories have developed sophisticated assays, using both “wet chemistry” and NIR (Near Infra-Red) technologies that quickly and accurately evaluate protein, fiber, various carbohydrates, and minerals in forages. Regular sampling of pastures throughout the year allows graziers and farmers to monitor the quality of the forages. Over a course of time, graziers can develop a combination of the best pasture grasses that work best for their climate and soil conditions. In the case of hay production, every cutting should be tested for its nutritional value. Farmers raising forages for the commercial hay markets who test their forages, generally have greater credibility than those who do not test.
Legumes such as alfalfa, clover, perennial peanut hay, and lespedeza all generally have higher levels of protein than grasses such as orchardgrass or timothy. In the early vegetative stage, legumes have higher leaf-to-stem ratios than grasses, resulting in higher levels of protein. Legumes also provide the added benefit of being “nitrogen fixers”, releasing absorbable nitrogen in the soil for later use by other crops. However, legumes are warm-season forages and go into dormancy during the winter. They prefer drier, well-drained soils, poorly tolerating muddy fields with standing water.
In the marketplace, protein levels for forages vary widely, ranging from as low as six percent to over 20 percent (on a dry matter basis). Livestock such as high producing dairy cows require protein levels over 20 percent — early vegetative. Horses do better with protein in the 15 percent range — a little more mature forage. Small ruminants also do well with protein ranging from 15 to 18 percent. Overfeeding protein in livestock should be avoided since excessive nitrogen must be disposed of through urine which requires additional dietary energy as well as the environmental issues associated with nitrogen pollution.
Fiber (NDF) levels rise quickly as forages mature. For legumes to be judged high quality, the NDF should remain below 40 percent (dry matter basis). For grasses, the NDF level should remain below 50 percent to be considered high quality. Grass forages with NDF levels over 60 percent provide only marginal nutrition for livestock.
A pasture or a field of grass standing three feet high, even though it contains many pounds to the acre, generally will have low nutritional value. People will be surprised how quickly a forage will mature in warm weather and go from 40 to 60 percent NDF in a very short period of time, diminishing the quality and value of the forage. Forages testing over 60 percent NDF will also have protein levels below 10 percent, making them a poor choice for livestock feed. Livestock owners must become familiar with the large variety of forages that are available and shop around to find the forage that best fits the nutritional needs of their animals at any given time.
What steps will you take to achieve high-quality forage production?