WINTER SURVIVAL IN ALFALFA
Whether you planed it originally or held off due to dry conditions in the fall, the time for spring planting alfalfa is just around the corner. Selecting the right seed is crucial, and two traits to consider are fall dormancy and winter survival. These traits are often treated the same, but are different. Today let’s look at winter survival.
Winter survival or winter hardiness is the ability for an alfalfa plant to make it through winter without injury, once the plant goes dormant. This is different than the fall dormancy rating that measures the alfalfa’s ability to prepare for and recover from dormancy. Winter survival is measured on a 1 to 6 scale with 1 being extremely hardy and 6 not hardy. For Nebraska, a winter survival rating of 3 is about as high as we want to go. There are free alfalfa ratings available online that may be helpful for comparison between varieties.
As temperatures drop and days shorten, alfalfa plants change their physiology to survive freezing temperatures and make it through winter. Increased hardiness can lead to reduced yield potential, but for a high dollar perennial forage, having a stand year after year is key.
In the past, winter survival traits were linked with fall dormancy. With new varieties, this isn’t always the case, so winter survival needs to be evaluated on its own.
We want to pick a winter survival ranking that will get us through winter without compromising yield. Where you are in the state plays a big role in what to pick. Winter temperatures affect the choice, but maintained snow cover is also important. As snow can help insulate the ground, parts of the state that regularly have open winters may need as high or higher survival rating than colder locations with winter-long snow cover.
Bottom line for Nebraska, a winter survival rating of 3 is about as high as we want to go and areas with open winters or regularly colder temperatures should be even lower.
DECIPHERING A HAY TEST: ADF and NDF – Brad Schick
Last week we looked at crude protein and how it is used for the rumen microbes and the animal. Today, we will look at neutral-detergent fiber or NDF and acid-detergent fiber or ADF.
Both NDF and ADF are part of a detergent analysis system used to analyze forages and their physical and chemical components. NDF measures how much of the forage sample is cell wall or fiber. This includes cellulose, hemicellulose, lignin, and silica portions of the forage which are the primary structural components. NDF is related to voluntary intake and rumen fill as well as how much energy is available to the animal. Usually, a low NDF results in higher energy available to the animal. As a forage plant matures, NDF increases and the forage quality decreases. NDF levels can vary from 80% in straw to less than 40% in early bloom alfalfa.
ADF measures cellulose and lignin, which, are usually the least digestible parts of the plant. ADF is related to the digestibility of the forage. This is used to calculate total digestible nutrients or TDN which will be covered next week. As ADF increases, the digestibility decreases. This means that high ADF forages are usually lower in energy. Alfalfa at early bloom has an ADF of 30-35% while a late bloom alfalfa has an ADF usually above 40%. Straw will have an ADF nearer to 50%.
NDF and ADF influence forage intake and digestibility. This can help predict animal performance by understanding how forage quality affects animal performance. We can also use this information to help decide when to harvest hay or what quality of hay to purchase.
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