This week, Victor Shelton has answers to the most asked questions for winter graziers. Thanks, Victor!
What is the difference between a frost and a freeze?
When water vapor condenses and freezes without first becoming dew, a thin layer of ice crystals form – this is frost. It generally has to be below 36 degrees to frost and include clear skies, moisture present and little wind. Plant tissue can be impacted, but not as severely as a freeze.
When the surface air temperature falls to 32 degrees or below, you have a freeze. Generally, if it is above 29 degrees, it is a light freeze that can kill most tender plants. If it is below 28 degrees, then it is considered a killing freeze or hard freeze – this freeze kills annuals and initiates shutdown of hardy perennials.
What are those forages that cause problems after a freeze?
With frosts and freezing conditions, we do need to remember that some warm-season forages such as sudangrass and sorghum-Sudan hybrids, and johnsongrass produce a cyanide compound when frosted, causing the production of the prussic acid. Once these forages are frosted, livestock should be removed for at least two weeks to allow for the forages to “dry down” and the prussic acid to dissipate before grazing again. Frosted areas could start with only “pockets” in a field. Any regrowth from the base of the plant after a frost can also be very high in prussic acid. It is just safer to avoid until forages are brown and dry – if in doubt, test before grazing.
Here’s more on potential poisoning hazards:
Nitrate and Prussic Acid Poisoning – It’s That Time of Year Again
When do forages go dormant?
After three hard freezes, most winter hardy perennial forages are dormant.
Forages going dormant is significant. USDA-NRCS defines stockpiling as ‘allowing standing forage to accumulate for grazing at a later period, often for fall and winter grazing after dormancy.’ The key word here is dormancy.
Once dormant, they can be grazed with less harm to energy reserves. We’ll be covering the ins and outs of how low you can go in December’s “Grazier’s Focus of the Month” so stay tuned!
What do I do if my forage isn’t dormant yet?
Forage plants are sensitive to grazing in the fall. That’s why I usually promote the use of annuals or crop residue, or ideally the combination of the two in the early fall. It allows the pastures to recuperate and build reserves.
If you don’t have annuals or crop residues to graze, then you always have the option of feeding hay for a while and then going back to grazing. Yes – that sounds a bit crazy. Why would I feed hay when I still have grass that could be grazed? Two reasons: first, you don’t want to hurt plant reserves impacting the stand for next year’s growth; second, you can potentially gain a lot more growth if moisture and fertility is in check with the increasing green solar panel.
How do I manage for the best nutrition in my winter forage?
Utilize less freeze tolerant forages first. Orchardgrass loses value fairly quickly after several heavy frosts and literally falls apart after several hard freezes. Tall fescues hold their value a long time and are the easiest and most ideal for long term stockpiling so save them for last.
I plan to do some pasture seeding/renovation. Do you have grazing management tips for successful seeding?
There are times or situations when grazing prior to dormancy or a killing freeze is what is needed. If you want to suppress spring growth, then grazing hard prior to dormancy can be beneficial. If you are frost-seeding clover into the field later this winter, this suppression of the grasses in the spring provides a longer window for the clover to grow and become established due to reducing the competition of the existing perennial grasses. I’ve also found fields that have become dominantly grass, especially a monoculture of tall fescue, can be grazed hard prior to early fall pre-dormancy and, if a good seed bank is present, you can have increased diversity – more clover the following year.
Do I have to continue managing grazing once grasses are dormant? Or can I let the cows run free?
Opening the gates and letting the cows roam freely all winter may make the cows feel adventurous and free but can hurt forage yields in the long run.
I highly recommend strip grazing the stockpiled forage once you start grazing it. If you have three sets of reels with poly-wire on them, enough step-in posts and connectors, you are in business. You generally want three sets: one set for that first break wire; the second set is for a back fence if needed; the third set is for the next day’s move and it’s always better to have that set up ahead of time. There is nothing like a group of impatient hungry cows complaining that you aren’t setting up that new fence fast enough. If you already have it set up and just need to open it up to them then they won’t care how long it takes you to move it for the next day. If you don’t believe me, ask the cows. We’ll try and discuss allocating that forage out next month.
Portable water is hard to manage during the winter. Do you have suggestions?
If you do not have portable water, then your stock may have to walk to a winter waterer. If this is the case, start strip grazing on the water end of the paddock and be watchful of excessive trailing. Trailing will occur when the same path is used over and over and may disturb or destroy forages in the path and open the area up to erosion. When it is a problem, consider adding new water points in the future and reseed any disturbed areas.
I challenge everyone to extend the time frame that they are grazing. Grazing is generally cheaper than most anything that you might feed; most nutrients are returned back to the soil where they were removed; and there is usually less mud to deal with over winter.
It is certainly possible to graze a very long time and reduce the amount of fed feed needed, but livestock numbers have to be in balance with your forage base to do so. That forage base can include corn residue, fall or winter hardy annuals, and hay aftermath once dormant.
Remember, it’s not about maximizing a grazing event, but maximizing a grazing season! Keep on grazing!
More pasture information and past issues of Grazing Bites are available here.