Cold weather and calorie requirements

Have you ever wondered how much of an impact the weather has on your horse’s calorie requirement?

While it is poorly documented in horses, observation suggests that the environmental conditions a horse is kept in can have a huge impact on their requirement for calories. Here are some of my (Nerida’s) personal observations:

Winter 2016 in the Hunter Valley, NSW, Australia

Winter 2016 was exceptionally wet and quite cold in the Hunter Valley. We really struggled to get weanlings to grow at ‘normal’ rates, even on maximum amounts of high quality feed with ample excellent quality pasture. The problem was worse on farms where paddocks were waterlogged and the weanlings simply couldn’t get dry and warm.

So instead of being able to partition calories toward growing, they were burning them all up just staying warm.

This year (2017) has been a very dry winter and weanlings are growing well on less feed and lower quality pasture. Same feed, same genetics, same farms, just different weather… and notably, not wet!

Autumn 2016 on the North Island of New Zealand

By contrast, the 2016 autumn season in New Zealand was unusually dry and warm. One farm, who had been using the same feed regime for several years (including the same quantity of feed for weanlings) started to experience weanlings with ‘contracted tendons’. There were a couple of new cases of weanlings ‘going over at the knee’ every few days. Needless to say the owners were concerned.

In the end, it came down to the weather. With the drier, warmer weather these little guys were burning less calories to stay warm and had more to use to grow and were just growing faster than they should have been. We reduced their feed and subsequent calorie intake and had no further cases.

Summer in Saudi Arabia

Broodmares and growing horses in Saudi Arabia who are housed outdoors with no air conditioning and are fully hand fed need less feed during the summer months (and excess body condition can be an issue). With such a high ambient temperature, they need virtually no calories to maintain body temperature. They also don’t move a lot because they are so hot. And this happens predictably every year.

I don’t rug my own horses so they are fully at the mercy of whatever the weather throws at them. Last year, during winter, it rained and rained. All of them had ribs showing (they are horribly easy keepers so this was exciting for me and a good thing!) by mid winter, despite having plenty of pasture available to them.

This year by contrast, it has been cold, but dry. And there is not a rib to be seen despite having been restricted to a very small part of their paddock with minimal (and I really mean minimal) pasture. The difference … rain!

As we saw in the Hunter Valley in the first example, horses can tolerate cold, dry weather easily. My horses demonstrated this perfectly this year. As soon as they get wet though, their insulation provided by their woolly winter coats that effectively traps heat close to their body is lost, PLUS when they are wet evaporative cooling (loss of heat from a wet surface) increases.

So it’s a double whammy; they can’t trap heat, plus they lose more heat. Which all combines to mean in cold, wet weather, their calorie requirement is significantly increased as they need to produce so much more heat (which they do by burning calories) to maintain their body temperature.

As you all know, calorie (or Digestible Energy) requirements vary horse to horse and are, as just discussed, also influenced heavily by the weather. So when using FeedXL, use the Digestible Energy requirement provided as a guide, but don’t be surprised if your horse is sitting above (i.e. needs more feed than is estimated) or below (needs less feed) the requirement you are given.

The only accurate way to know if your horse is getting enough calories is to use your eyes and your hands. Body condition score your horse regularly and adjust the amount of Digestible Energy in the diet up or down if your horse starts to lose or gain weight.

Or you might be like Sam and I and a whole lot of our FeedXL members and feel like you are constantly adjusting calorie intake down and making zero impact on how overweight your horses are! And like us you might then just wait and hope the next winter is wet and cold!!

Some more information about Body Condition Scoring is here for you: http://feedxl.com/1-why-body-condition-score/

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