The Effect of Pellet Size on Voluntary Food Intake in Young Pigs


Involuntary food intake in the young pig in the days after weaning is very variable. This is crucial time however as low voluntary food intakes van lead to reduced digestive efficiency due to adverse structural changes in the gastro-intestinal tract. One approach to try to simulate intake in the young pig is to manipulate the physical form of the diet with regards to pellet size.

Materials and methods:

240 Large White x (Landrace x Duroc) pigs were used with approximately equal numbers of male and female animals. The trial was conducted over 4 blocks each consisting of 6 sows and their litters. Litters were standardised at birth to 10 piglets per sow. Piglets entered the trial at birth and remained on trial until approximately 56 days of age. Sows and litters were housed in conventional farrowing crates with an enclosed heated creep area until weaning at 28 days of age. After weaning the piglets were moved into weaner accommodation and housed in groups of 5 in traditional flatdeck accommodation, with fully slated floors.

The treatments were offered in a 2×3 factorial design with all litters receiving either a pellet 1.8mm or 5.0mm in diameter in the farrowing house followed by each pen receiving either a 1.8mm, 2.4mm or 5.0mm diameter pellet in the weaner accommodation. All possible combinations were accounted for. All pellets for the same stage of growth were made to the same formulations with the only difference being pellet diameter. Food was offered on an ad labium basis.

Production and behavioural data were collected at key stages, at the introduction of creep feed, at the point of weaning and at the subsequent weekly intervals. Production data was analysed using an analysis of covariance with either creep or weaning weight as the covariant.


All food was consumed by the piglets in normal quantities with no apparent differences between the treatments in terms of piglet health. The mean piglet weights, feed consumption and performance are displayed in table one. There were no significant differences between the treatments in piglet weights at the changeover from the stage 1 to stage 2 food (mean 9.43kg, s.d. 4.72) or at the end of the trial (mean 19.47, s.d. 10.27).

There were no significant differences in food intake, liveweight gain or FCR of the piglets at any stage of the trails between treatments. There were no significant differences between the replicates or any significant sex treatment interactions.

Table One – Effect of pellet diameter on piglet performance


Effect of treatment on all production variables was not significant (p<0.05)

Although there were no significant differences between the treatments in terms of production data, the behavioural responses of the pigs to the different pellet sizes was interesting. In the farrowing house piglets receiving the 5.0mm diameter pellet spent significantly more time engaged in feed related behaviour than the litters receiving 1.8mm pellets (see table below). In the weaner accommodation however this tend appeared to be reversed with piglets on the 1.8mm diet spending significantly longer at the trough, this effect however was only significant up until one week postweaning.

Table Two – Effect of pellet size on time spent eating creep feed (proportion of a three hour period)


Figures in the same column bearing different superscripts are significantly different (p<0.05)


From the trail data it can be seen that piglets will consume pellets of 1.8mm – 5.0mm diameter as readily as each other. This is in contrast to popular beliefs that the smaller pig will show a preference for smaller pellets. The piglet also appears very adaptable to changes in diet presentation. Groups of pigs who were offered two different pellet sizes during the trial had similar growth rates and feed intakes to those piglets fed on one pellet size throughout the entire trial.

In contrast however, pellet diameter did significantly effect feeding behaviour. The litters of piglets fed the 5.0mm diameter pellet as creep feed spent significantly longer at the through than those fed pellets of 1.8mm diameter. These piglets however did not show improved growth rates to weaning. It appears therefore that while the presentation of the diet can attract the piglet to the feeder it does not improve the feed intake.

Date published: 2003-01-01

H.L. Edge 1, J.A.
Dalby1, P. Rowlinson1, M.A.

SCA Nutrition Ltd