A new pen concept to house gestating sows in groups has been devised in Denmark. Given the name of the Opti-pen, it combines group accommodation with individual feeding and the supply of straw bedding on a drained floor. Our work with the design has shown that it is possible to establish a pen for gestation in which the sows are provided with feeding/resting stalls and a large, well-bedded lying area — yet the total amount of space occupied is the same as used in group yard facilities equipped for electronic sow feeding.

Investigations of the Opti-pen, in a development project under the Danish Applied Pig Research Scheme, have looked at 3 different designs that were similar in principle and differed only in the size of the lying area. The overall available space varied from 2.7 to 3.3 m2 per sow. In space terms, the pen therefore uses less than a layout that provides feeding stalls for all the sows and is competitive with electronic sow feeding (ESF) yards.

A choice of eating places

In the Opti-pen, one feeding point is provided for each sow, but there are 2 feeding systems in the same pen. Feed is provided either in the feeding/resting stalls placed on one side of the pen or in a long trough on the other side, offering group feeding from long troughs as well as individual feeding in the stalls where the sows can both eat and rest. Locks on these stalls can keep the sows inside during feeding, unable to change places.

Group-housed sows should all be fed at the same time to avoid unrest. We believe the best way to achieve this is normally by giving the feed in a dry form. However, the layout tested in our trial has been wet-fed because the herd involved uses liquid feeding for its sows.

It was decided to divide the total daily feed allocation into 2 parts that could be fed consecutively, in order to minimise the period of waiting for access and so maintain calm at feeding times. First, the sows in stalls were given half of their day's portion. Those eating from the long trough received their own initial installment soon after. Then it was the turn of the sows in stalls to have the rest of their allowance and finally those at the trough.

During the trial we watched to see which feed access point the sows would choose. From our observations it seemed that the animal's choice was linked to its age. While their younger counterparts were less selective, the older sows preferred to eat always on the same side of the pen at each meal-time. Of course, it meant they consistently used the same feeding system as well, whether in the stalls or at the trough.

Remember that each feed cycle started with the feeding/resting stalls. It probably accounted for the fact that they were chosen by the older and higher-ranking sows in the peck order. However, this was seen as an advantage for the sows eating at the trough because the end-result was a calmer feeding situation.

A delayed start

The trial has shown that sows in an Opti-pen stay in reasonable body condition and the level of hygiene in the pen remains satisfactory. Few sows have needed to be culled. Overall, the design was judged to be suitable for housing sows in stable groups during gestation with provisos. One is that the members of the group need to be uniform for their physical condition. The other caution states that they should be penned separately for the first 4 weeks after mating.

Why not go directly into an Opti-pen when mated? Group feeding immediately after service may reduce the subsequent litter size. Group feeding also made heavy demands on the liquid-feed system at the herd, because it had to split the daily allowance into 2 meals and to finish feeding one pen before starting to give feed to the next group. The allocation of feed should be more efficient if the pens are dry-fed when all the sows in each pen can be fed at the same time.

The main part of the lying area remained clean. The pen design made use of the fact that sows like to lean against an edge such as the lip of a trough to support themselves when they start to lie down. It may explain why, in the trial, the lying area was always dry and clean around the trough.

This area is large, due in part to the trough's placement on the side of the pen, and it was given a good level of bedding. It was not possible to keep the straw bed completely free of manure, but the level of hygiene in the lying area depended both on its size and on the stocking density in the pen.

Size and straw

The pens had a total of 1.3m2 of lying area per sow, when a percentage of the solid floor in the feeding/resting stalls was included. Available space in the lying areas outside the stalls varied from 1m2 to 1.5m2 per sow. The best hygiene was obtained with approximately 1m2 of lying area for each sow. All the sows could be together in the lying area.

Straw usage in the Opti-pen worked out at 130-150kg per pig-place per year. That is significantly less than normally used in gestation facilities with deep litter, but more than the amount associated with yards for electronic sow feeding. The calculation would be important when building a new sow-house because its manure system must handle the expected straw consumption.

Another requirement is the installation of a scraper-type barn cleaner to remove the soiled bedding. In our trial the straw bed covered the whole of the lying area — partly to increase the non-slip properties of the floor and partly to make the lying zone attractive. It certainly worked in the sense that the sows often used the lying area. However, the pen could be improved by further developing the floor profile or the design of the lying area to reduce the consumption of straw.

Perhaps there is also an alternative to the long trough. Individual feeding arrangements for the sows could be provided by having a trickle-feeding (biofix) system on the opposite side of the pen to the feeding/resting stalls. Or, the design might be modified to have feeding/resting stalls in rows on both sides of the pen. It should be achievable, if the second bank of stalls could be lifted clear of the lying area when not in use at a meal-time.  PIGI