18/06/2025
Il pascolo è una questione seria, da non liquidare come un'ovvietà per un erbivoro. Fatelo controllare ciclicamente
🌱 𝐆𝐫𝐚𝐬𝐬 𝐢𝐬 𝐜𝐨𝐦𝐩𝐥𝐞𝐱 – 𝐚𝐧𝐝 𝐬𝐨 𝐢𝐬 𝐠𝐫𝐚𝐳𝐢𝐧𝐠 𝐦𝐞𝐭𝐚𝐛𝐨𝐥𝐢𝐜 𝐡𝐨𝐫𝐬𝐞𝐬 🐴
After a lively discussion in the comments on my recent post about NSCs (nonstructural carbohydrate) and pasture height, I wanted to follow up with a deeper look at the many factors that influence pasture safety, especially for sugar-sensitive horses.
One of the biggest misconceptions I see is the belief that there’s a universally “safe” time or type of grass for all horses with metabolic issues. While NSC concentrations can sometimes be lower, that doesn’t automatically make the pasture safe. Even reduced levels can exceed what sensitive horses can tolerate, because safety depends on more than just the numbers.
And here’s the challenge: there’s no consistent way to predict it. NSCs are highly variable, even on the same pasture, within the same day. Below are just a few of the factors that can influence these fluctuations in pasture NSC.
🌅 𝐓𝐢𝐦𝐞 𝐨𝐟 𝐃𝐚𝐲:
During daylight hours, photosynthesis creates NSCs faster than they can be used. However, after sunset, respiration uses up the stored sugars. As a result, NSCs can accumulate throughout the day, being the lowest around sunrise and the highest near sunset.
📖 McIntosh, 2007
🌤️ 𝐒𝐮𝐧𝐥𝐢𝐠𝐡𝐭 (𝐒𝐨𝐥𝐚𝐫 𝐑𝐚𝐝𝐢𝐚𝐭𝐢𝐨𝐧):
Beyond just the time of day, the amount of sunlight matters. On cloudy days, NSC accumulation can be lower due to reduced solar radiation. So, weather impacts sugar levels too—not just the clock.
📖 McIntosh, 2007
🌱 𝐆𝐫𝐨𝐰𝐭𝐡 𝐑𝐚𝐭𝐞:
NSCs fuel plant growth. So, when grass is actively growing, it uses up its stored sugars. Fast-growing grass (like freshly mowed, fertilized, or well-watered pasture) tends to have lower NSCs. But stressed, short grass (whether from drought, heat, or overgrazing) may not be able to use up these NSCs as efficiently.
📖 Siciliano et al., 2017
🌾 𝐌𝐚𝐭𝐮𝐫𝐢𝐭𝐲:
This one’s tricky. Generally, as grasses mature, their NSC concentrations decrease due to dilution by fiber. But some mature forages still hold high NSC levels. Also, horses grazing taller grass tend to take larger bites, which can increase total sugar intake, even if the percentage is lower. This means maturity is an unreliable indicator of pasture NSC.
📖 Edouard et al., 2009
🌷❄️ 𝐒𝐞𝐚𝐬𝐨𝐧:
Spring grass is often highest in NSCs, triggering strong glucose and insulin responses. Mowing during this period may help reduce risk. In fall, first frosts can spike NSC levels as low temperatures below 40°F (4.4°C) slow or stop sugar metabolism in plants, leading to buildup.
📖 McIntosh, 2007; Siciliano et al., 2017
🍀 𝐅𝐨𝐫𝐚𝐠𝐞 𝐓𝐲𝐩𝐞:
Different forage species store carbohydrates differently. Specifically, warm-season grasses and legumes (such as alfalfa) utilize a self-limiting carbohydrate storage mechanism while cool-season grasses can store as much as they want!
📖 DeBoer et al., 2018
🐴 𝐈𝐧𝐝𝐢𝐯𝐢𝐝𝐮𝐚𝐥 𝐇𝐨𝐫𝐬𝐞:
Many factors related to the horse itself can influence how they respond to NSCs - things like diet, age, body condition, breed, genetics, and exercise. Science gives us a strong foundation, but every horse is an individual with its own tolerance levels and triggers. That’s why blanket statements don’t work. It’s essential to work with a veterinarian or a qualified equine nutritionist to build a plan tailored to your horse.
📖 Pratt et al., 2006; Bamford et al., 2014; Rapson et al., 2018; Pratt-Phillips, 2024
🔍 𝐀𝐧𝐝 𝐥𝐞𝐭’𝐬 𝐧𝐨𝐭 𝐟𝐨𝐫𝐠𝐞𝐭
Healthy horses without metabolic concerns are generally well-equipped to handle grazing, especially when pasture is managed thoughtfully. Their bodies regulate insulin and glucose effectively, and grazing supports natural behavior, movement, and mental health.
🔬 𝐒𝐨 𝐰𝐡𝐚𝐭’𝐬 𝐭𝐡𝐞 𝐬𝐨𝐥𝐮𝐭𝐢𝐨𝐧?
👉 Know your horse. Know your pasture. Test when you can.
👉 Use tools like grazing muzzles, dry lots, and turnout timing strategically, not just based on a chart.
👉 Be flexible and smart. What was safe last week or even yesterday, might not be today.
📌 𝐁𝐨𝐭𝐭𝐨𝐦 𝐥𝐢𝐧𝐞:: Grazing for metabolic horses isn’t straightforward, it’s an ongoing conversation between science, observation, and the horse in front of you. NSC levels are influenced by multiple, overlapping factors that can’t be reliably predicted. While the safest option is to avoid grazing altogether, some horses have done well with carefully managed, responsive plans tailored to their forage, their physiology, and their environment.
There is still a LOT we have to learn. What would you like to see reaearch evaluste next?
Cheers,
Dr. DeBoer
𝘼𝙣𝙙 𝙄 𝙝𝙖𝙫𝙚 𝙖 𝙥𝙤𝙨𝙩 𝙛𝙧𝙤𝙢 𝘼𝙥𝙧𝙞𝙡 𝙩𝙝𝙖𝙩 𝙙𝙞𝙫𝙚𝙨 𝙞𝙣𝙩𝙤 𝙩𝙝𝙚𝙨𝙚 𝙧𝙚𝙨𝙚𝙖𝙧𝙘𝙝 𝙥𝙧𝙤𝙟𝙚𝙘𝙩𝙨 𝙢𝙤𝙧𝙚 𝙞𝙣 𝙙𝙚𝙥𝙩𝙝 𝙞𝙛 𝙮𝙤𝙪 𝙬𝙖𝙣𝙩 𝙩𝙤 𝙘𝙝𝙚𝙘𝙠 𝙩𝙝𝙖𝙩 𝙤𝙪𝙩!
McIntosh BJ. Circadian and seasonal variation in pasture nonstructural carbohydrates and the physiological response of grazing horses.
Siciliano PD, Gill JC, Bowman MA. Effect of sward height on pasture nonstructural carbohydrate concentrations and blood glucose/insulin profiles in grazing horses. Journal of Equine Veterinary Science. 2017 Oct 1;57:29-34.
Edouard N, Fleurance G, Dumont B, Baumont R, Duncan P. Does sward height affect feeding patch choice and voluntary intake in horses?. Applied Animal Behaviour Science. 2009 Jul 1;119(3-4):219-28.
DeBoer ML, Hathaway MR, Kuhle KJ, Weber PS, Reiter AS, Sheaffer CC, Wells MS, Martinson KL. Glucose and insulin response of horses grazing alfalfa, perennial cool-season grass, and teff across seasons. Journal of equine veterinary science. 2018 Sep 1;68:33-8.
Pratt SE, Geor RJ, McCutcheon LJ. Effects of dietary energy source and physical conditioning on insulin sensitivity and glucose tolerance in Standardbred horses. Equine veterinary journal. 2006 Aug;38(S36):579-84.
Bamford NJ, Potter SJ, Harris PA, Bailey SR. Breed differences in insulin sensitivity and insulinemic responses to oral glucose in horses and ponies of moderate body condition score. Domestic animal endocrinology. 2014 Apr 1;47:101-7.
Pratt-Phillips S. Effect of Exercise Conditioning on Countering the Effects of Obesity and Insulin Resistance in Horses—A Review. Animals. 2024 Feb 26;14(5):727.
Rapson JL, Schott HC, Nielsen BD, McCutcheon LJ, Harris PA, Geor RJ. Effects of age and diet on glucose and insulin dynamics in the horse. Equine Veterinary Journal. 2018 Sep;50(5):690-6.
