08/07/2026
Well worth a read
With this dry weather, many farmers are cutting their fields for hay.
After last year’s shortages, lots of owners are keen to get their hands on new hay as soon as possible — but this often brings up the old advice that “𝑦𝑜𝑢 𝑠ℎ𝑜𝑢𝑙𝑑𝑛’𝑡 𝑓𝑒𝑒𝑑 ℎ𝑎𝑦 𝑓𝑜𝑟 𝑎𝑡 𝑙𝑒𝑎𝑠𝑡 𝑠𝑖𝑥 𝑤𝑒𝑒𝑘𝑠.”
So what does the science actually say about this?
Well, in short: 𝐢𝐟 𝐲𝐨𝐮𝐫 𝐡𝐚𝐲 𝐢𝐬 𝐩𝐫𝐨𝐩𝐞𝐫𝐥𝐲 𝐦𝐚𝐝𝐞, 𝐭𝐡𝐞𝐫𝐞’𝐬 𝐧𝐨 𝐢𝐧𝐜𝐫𝐞𝐚𝐬𝐞𝐝 𝐫𝐢𝐬𝐤 𝐢𝐧 𝐟𝐞𝐞𝐝𝐢𝐧𝐠 𝐢𝐭 𝐬𝐭𝐫𝐚𝐢𝐠𝐡𝐭 𝐚𝐰𝐚𝐲
(no more than introducing any other feed — gradual changes are always best where possible).
The six‑week rule comes from a time when hay was stacked in huge, dense ricks that could heat internally for weeks. Waiting wasn’t about horse digestion — it was about preventing fires and spoilage. Modern baling and storage simply don’t behave the same way.
What really matters is moisture. Properly cured hay — dry matter around 85% and moisture below 12–15% — becomes biologically stable very quickly. Once it’s dry and cool, microbial activity drops to almost nothing, meaning the hay isn’t fermenting, heating or changing in a way that would make it unsafe.
Heating only happens when hay is baled too wet. Moisture above ~18–20% can lead to caramelisation, mould growth and nutrient loss. That’s a moisture problem, not an “age” problem.
Some horses do get gassy when switching to new hay, but this is usually because the nutrient profile has changed — for example, moving from late‑cut to early‑cut hay, or from low‑sugar to higher‑sugar forage. It’s the type of hay that matters, not whether it’s “new.”
So the real red flags are simple: hay that’s still warm inside, smells sour or musty, feels damp, or looks mouldy. If it’s dry, cool and clean, there’s no evidence‑based reason to delay feeding it.
𝐼𝑚𝑎𝑔𝑒 - 𝑡𝑟𝑎𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 ℎ𝑎𝑦𝑠𝑡𝑎𝑐𝑘𝑠 𝑖𝑛 𝐼𝑟𝑒𝑙𝑎𝑛𝑑