Thermoregulation from Tomakomai to Taroom or -20°C to +40°C

Early February was a busy time for Dr Stewart. After ten days in Japan, Jen landed in Australia to then spend the next 14 days on the road in SE Queensland visiting several equine veterinary clinics and stores along the way. This weeks blog is a snippet of her trip and touches on some of the topics she covered…

February found me looking at pregnant mares, new foals, yearlings and 2 year olds in -20°C and 3 metres of snow – all living outside for at least 20 hours a day and only the little foals have quarter rugs. Their winter coats are thick and luxuriant, and they happily play and do normal horsey and foaly things. Certainly, when its wet and windy they have shelter but are rarely seen in it otherwise. I’m being a serial pest re rugs, but if there is no reason to use them (insect protection, clipping, old age or veterinary conditions) horses can be quite comfortable to around minus 10°C ° to minus 15°C if they have plenty of 24-hour access to hay or other roughage.

 The morning I left Japan it was -17°C at 10am (I was wearing everything I owned plus gloves, thermals, beanie, scarf, ski pants and snow boots). I arrived to +34°C in Sydney with just enough time to empty my suitcase of cold climate gear and replace with items suitable for central Queensland. My bag was much lighter! The snowy ground, woolly horses and deciduous trees were replaced with bare paddocks and cattle and horses on travelling stock routes – where they move around 10km a day for up to 12 months in search of feed.

 Feedstuffs are limited in drought times (similar to northern hemisphere winters when there’s 3m of snow!) and I was so impressed with how people deal with feed shortage – whether from drought, crop failure or flooding. In Queensland I spoke at several veterinary clinics and produce stores, and recently wrote an article on drought feeding in Equine News - which you may find helpful if you need some ideas for when feed is in short supply. I also spoke on 3 of my greatest professional and personal interests – colic, laminitis and osteoporosis. Because the major risk factor for colic is a change in diet, go slowly with any changes you need to make if feed is hard to come by.

 Another situation where a change in diet can occur – and this time it’s unknown to us — is when pasture sugar levels change. We so often see cases of laminitis that just appear out-of-the-blue and have us searching for the triggers. Ongoing research into plant sugar levels has shed some light on how diet (and sugar intake) can change even when we haven’t made any changes! So, the first thing to understand is that plants are ‘sugar factories’ – the purpose of photosynthesis is to produce sugar for the plants, and that the amount of sugar in the grass is the balance between sugar production (sunlight) and sugar usage (plant growth: warmth, water and fertiliser). So, if production is greater than growth (lots of sun but cool, dry) then plant sugar levels will be high – but if growth matches production, there will be little left over sugar in the plant. A few facts to keep in mind about supply and demand or production vs growth are: when night time temperatures dip below 5°C (growth slows so sugar not used up), the chances of sugar being very high the next day are too great to gamble on allowing a horse with a history of laminitis to graze; sugars in perennial rye grass double within 3 hours of sunlight (due to increased photosynthesis and sugar production); on warm nights when growth can continue, Pangola grass sugar declines by 78% whereas at 10C when it’s too cold for growth they drop by only 2%; the speed at which the drought comes on also affects plant sugar levels e.g. sugars in Setaria can double if the drought comes on slowly i.e. growth slows due to water deficiency but photosynthesis continues; many broadleaf weeds are even higher in sugar than are grasses – so we mustn’t assume they are safe.

I met many wonderful people– with a shared passion for horses. If we can help you in any way with your horse’s health and with clinical nutrition for veterinary conditions, please be in touch.