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Our Newsletter

2008 Teaching Techniques

Is Dead Grass Safe to Graze?

Going to be doing more educational ground sessions with your students this winter? Why not try teaching some pasture management concepts as they relate to horses with certain needs. Let this article by Kathryn Watts help you in your research.

Many of us with laminitic horses look forward to when our pastures die so that we can turn them out longer each day. We have learned that near freezing nights in fall can cause sugars to sky rocket, so horses at high risk for laminitis should be pulled off grass during this time. Winter often means weather and footing that makes riding impossible, so it’s even more important for my horses to have a reason to wander about the paddock instead of standing in the run-in shed all day to escape the nasty weather. While my insulin resistant ponies can only eat the improved grass in their paddock for an hour or so during summer, they are able to eat it for 3-4 hours per day by late winter. During fall, when cold nights cause sugar to build up, they are not allowed any access to green grass. All that stockpiled forage that grew in the fall will not go to waste, because once it is completely dead, rain and snow can leach out the accumulated sugars.

Many people ask ‘when is it safe to graze?’ Like many others things concerning management of laminitic horses, I learned this the hard way. One year in mid December, I turned my ponies out on a grass paddock that was nearly all dead. By the second day, they were sore footed again! Because they were barefoot at the time, I called my farrier to put their therapeutic support shoes back on. He told me that his own chronic laminitis cases recently got sore on dead grass. So I asked him to send me some of the grass in a cooler on ice; which I froze as soon as it arrived. I also started sampling some of the dead grass in my research plots. Some of the samples still had some green, living tissue at the stem bases even though it had been below 0 F. Stem bases are a storage organ for sugars in grass, so this will have the highest concentration of sugar. I sent the frozen samples overnight with dry ice to Dairy One for analysis. The results were quite surprising. This dead grass had some of the highest water soluble carb (WSC) concentrations I had ever seen.

That fall was a bit unusual. We were in the midst of a several year long drought. Once we were done sampling the research plots for the year, I stopped irrigating them. We had some terrible wind storms that fall, mixed in with dramatic drops of temperatures below 20F that killed the grass very quickly. The grass was desiccated; looking more like dark green hay than usual brown dead grass. It was freeze dried! That’s the perfect way to preserve the sugar in grass. The drought continued though fall and early winter, with no measurable rain. An occasional inch of dry snow evaporated into the cold, dry air without melting. The leaching of sugars that usually occurs for stockpiled forage just didn’t happen that year because we had no precipitation.

This year (2007) winter has come early, and the drought has broken. By the end of November, my west paddock was 90% dead and the east paddock was about 50% dead. We had some rain after hard freezes that killed off most of the grass, then it got really cold (-0F) and windy and it snowed. I was anxious to turn my bored ponies out for some much needed exercise. The first time, I let them out for about 20 minutes, and I watched where they grazed. Sure enough, they went straight to the spots in the paddock where the grass had the most green. For years I’ve been testing what they choose to eat first, and it’s always the highest in sugar compared to the rest of the paddock. To make sure the grass was suitable; I pulled some samples, froze them, and shipped them frozen, overnight to Dairy One. This time I pulled one sample from the greenest spots (about 75% brown, 25% living and green), and another from the brownest spots, which were pretty much completely dead.

WSCs will not wash out of grass until it is completely dead and brown. Then you have to have enough rain or melting snow after it’s completely dead to leach the sugar out. Until then, please take care with your high risk horses. Proceed with caution, and allow them to acclimate slowly, just as you would if it were June. It might be best to assume that any green grass that has been subjected to repeated freezing nights is candy - full of sugar, even if there is snow on top. If it’s still green, the rain or snow cannot leach out the sugar. CHA

About the Author: Kathryn Watts has a BS in Crop & Soil Science from Michigan State University and over 25 years experience in agricultural contract research and consulting. She operates her own company, Rocky Mountain Research and Consulting, Inc. in Center, Colorado. Visit her website at www.safergrass.org.