Chaff slows eating.
Horses are naturally adapted to
eat roughage. It takes longer to eat and digest
than concentrate feed.
It has become popular to add
chaff or chopped straw to concentrate feed to
make horses eat it more slowly. But there has
been little scientific work to demonstrate that
the practice has the desired effect.
Now a study by Dr Andrea Ellis,
of Nottingham Trent University, and co-workers at
Waltham ® and Spillers ® shows that it does.
They measured the time taken for
horses to eat 1kg of various feeds and the
average number of chews per minute. They
evaluated the effect of including 10%, 20% or 30%
of straw, chopped into either 2.5cm or 4cm
lengths, to a trial pellet fibre mix (containing
10% short cropped lucerne).
The rate of chewing remained
about the same regardless of the type of food
fed. But the type of food had a significant
effect on the rate of intake and the total number
of chews per kg.
Diets containing added straw were
eaten much more slowly than their normal diet
mix, (containing 50% pellets, 15% lucerne-straw
chaff, and 35% soaked sugar beet pulp), their
normal diet and the trial pellets on their own.
There was no significant effect of increasing the
straw content above 20%, although the intake rate
did decrease, leading to an increased time spent
on feed intake for 1kg of feed as illustrated
So adding chaff can result in
horses spending more time eating their
This could have health benefits
for the horse. Increased buffering by saliva in
the stomach may reduce the risk of stomach
ulcers. Choke may be less likely because of more
saliva being mixed with the bolus of food, and
the food being eaten more slowly and chewed more
One interesting finding was that
the normal diet mix was eaten more quickly than a
trial diet containing similar amounts of chaff
(but without the sugar beet pulp). The
investigators suggest that this was probably due
to the higher moisture content when the soaked
sugar beet pulp was included. Chopped straw may
only have a beneficial effect in slowing intake
if it is added to a high dry matter diet. The
investigators suggest that this is an area that
needs more research.
Source: Equine Nutrition
Further reading: Adding chopped
straw to concentrate feed: The effect of
inclusion rate and particle length on intake
behaviour of horses. Andrea D Ellis, Samantha
Thomas, Kate Arkell, Patricia Harris. Proc Equine
Nutrition Conference Pferdeheilkunde (2005) 21,
35 - 37.