The bottom line is forage quality begins in the field and ends with maximum animal performance, says University of California (UC) Cooperative Extension Farm Advisor Shannon Mueller, Fresno County.
Mueller says forage quality is not an intrinsic value of the plant alone; it is based on the combined effects of the plant and animal management.
Forage quality and how to improve forage in the field were discussed by Mueller and Dan Putnam, UC statewide alfalfa and forage Extension specialist, Davis, Calif., during a hay seminar at the 2010 World Ag Expo in Tulare, Calif. in February.
Mueller says different ideas exist on what determines forage quality.
“Some people focus on the chemical analysis, especially the total digestible nutrient content (TDN),” Mueller said. “To others it’s the appearance of the hay; they want weed-free hay with a good green color. Others just want to know how the forage milks.”
Forage quality is a combination of all three qualities, Mueller says.
A standard laboratory chemical analysis reveals vital information on the dry matter, crude protein, plus acid and neutral detergent fiber. Additional analyses can include in-vitro tests, and determining rumen undegradable protein, starch, lignin, and mineral levels.
The information reveals the relative feed value, TDN, relative forage quality, net energy of lactation, metabolizable energy, and other calculated values.
A visual examination of forage reveals the plant’s maturity status at harvest and weed content. Weed information is importance since some weeds can damage animal mouthparts and other poisonous weeds can cause death. That is why Mueller recommends visual and lab analyses to judge the quality.
“Ultimately we are looking at animal performance,” Mueller said. “The underlying issue is how the animal responds to forage in overall milk, meat, and wool production, plus the animal’s overall health.”
Animals can lose interest in feed based on anti-palatability factors including poor texture (hard stems and coarseness), unpleasant odors, and overheated forage.
The potential feeding value of forage depends on the plant species, maturity, leaf-stem ratio, pests, climate, soils, and weeds. Potential animal performance depends on the species, breed, genetics, age, sex, lactation stage, and health.
Forage quality is actually a function of intake — “the fill factor” and energy.
“Hay intake boils down to the intake and digestibility of forage,” Mueller said. “If the forage fills the animal’s rumen, but fails to pass through it quickly, it’s similar to a Thanksgiving dinner where you can’t eat another bite. You’ve actually limited the potential animal performance because they do not continue to eat.”
Alfalfa hay energy is determined by rapidly-degrading soluble sugar, starch, pectin, protein, and slowly degraded fiber. Determining the digestibility of fiber and protein in the rumen is important.
Dan Putnam says growers can improve forage quality in the field to maximize animal performance. Among the primary mechanisms to produce high quality hay is plant maturity, a high leaf-to-stem ratio, excellent weed control, and harvesting skills. Weather and temperature have an impact which growers cannot control.
The leaf is where the majority of plant proteins and energy are located, Putnam says. Leaf yields level off after 15-20 days in the growth cycle while stem weight continues to increase. Stems are high in fiber but low in protein, and have higher undigestible lignin as the plant gets older. This is why cutting schedules are so important in influencing alfalfa quality.
Most weeds in hay, especially grasses, can lower forage quality and reduce consumption. Weed control is crucial.
“Animals have been killed by weedy alfalfa fields,” Putnam said. “Some weeds are very toxic, including fiddleneck and groundsel, which contain poisons for animals, and others such as foxtail can irritate animal mouthparts. Weeds are also a perception problem; hay customers don’t like to see weeds in the hay.”
Alfalfa hay harvested in the spring and fall tends to have less fiber and higher TDN levels than summer harvests. Cool temperature growing regions including the intermountain areas tend to produce higher total energy values, but slightly less protein. Higher temperatures hasten crop maturity and increase plant respiration.
Harvesting forage in the late afternoon can result in slightly higher TDN values than a morning harvest.
Rain damage can cause a 10 percent to 20 percent loss of dry matter and quality, Putnam says. A field study in Wisconsin showed up to a 50 percent dry matter loss under heavy rainfall conditions.
Harvesting and conditioning are important issues. Putnam says leaves dry down faster than stems. Leaves can fall off and become shattered during the harvesting process. Hastening the dry down can be beneficial.
Does fertilizer improve alfalfa?
“Most fertilizers increase the alfalfa yield when an element is limited in the soil,” Putnam said. “In general, there is little evidence that fertilizers significantly improve forage quality, but they are very important for yield.”
Growers should not use nitrogen fertilizers on alfalfa, says Putnam.
Pests and diseases can reduce leaf percentage and quality. Alfalfa weevils are leaf chewers which usually degrade alfalfa quality. Leafhoppers can reduce the stem growth but strangely increase quality since the stem yields are lower.
A slightly higher TDN is generally found in water-stressed alfalfa.
In alfalfa varieties, Putnam says some varieties are superior in quality by one to two points at the same cutting schedule.
“Yield is probably the most important factor for variety selection followed by disease resistance and persistence, and then quality potential,” Putnam said. “I would choose varieties primarily on the yield potential and then look at quality factors as a secondary consideration.”
Putnam calls sampling the most important cause of errors in a forage-quality evaluation. He recommends a single hay test. Taking grab samples can misrepresent a hay lot.
Putnam’s recommended sampling checklist includes:
• Use a very sharp coring device with a three-eighth to three-quarter-inch diameter to cut through the hay.
• Insert the device into the butt ends of bales between the ties, not the sides.
• Gather random samples. Every fourth or fifth bale is fine, but sample the entire stack.
• Get a least 20 cores; composite them together.
• Gather a half-pound sample.
• Do not leave samples on the truck dash in the hot sun.
• Only use a certified lab.
• Ask the lab to grind the entire sample.
• Make sure you can certify the hay sample using a free on-line test.