The “80:20 rule”

There’s been a lot of discussion recently about the so-called 80:20 rule of forage feeding – or feeding 80% of your horse’s hay allowance in the day and 20% at night. Ultimately, it’s not wrong BUT it’s the definition of “night” that’s important.

What does the research say?

A lot of this has stemmed from a research paper published in the Equine Veterinary Journal in 2009 by L. Husted et al. In the study, they fasted a group of horses for 12 and 24 hours while monitoring the pH of the upper portion of their stomach. Predictably, stomach pH dropped (became more acidic) when food was withheld BUT they found that this natural fasting behaviour happened in stabled horses overnight even when offered ad lib hay.

The study found that the horses offered ad lib hay ate 63% of their total daily hay intake between 9am and 9pm and had a correspondingly lower stomach pH between 3am and 9am. So yes, horses do naturally eat less overnight and it makes sense to take this into account when allocating forage amounts. HOWEVER, your horse’s idea of “night” may be different to yours – 9pm onwards is when they show reduced feeding behaviour. They eat a significant amount of their daily hay amount during the early evening.

What do I recommend ?

For me, wherever possible I recommend allowing ad lib forage feeding. Grazing is a huge part of normal horse behaviour and a key component in good welfare. It’s up to us to find a forage source that matches their nutritional needs and allows our horse’s to eat a normal volume while avoiding excess calorie, starch and sugar intake. Tricky, I know, but definitely possible.

Ref: Husted, L., Sanchez, L. C., Baptiste, K. E. and Olsen, S. N. (2009) Effect of a feed/fast protocol on pH in the proximal equine stomach. Equine vet. J. 41 (7), 658-662.

Equine squamous gastric disease.

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