The Challenge of Gestating Sows:

The common feature of all gestation management systems is a means of controlling nutrient intake by the animals. Currently, the most common means of controlling intake is individual penning in stalls. However, it is clear that stalls violate one of the criteria for high welfare systems, that is, freedom of movement. 'An animal should at least have sufficient freedom of movement to be able without difficulty, to turn round, groom itself, get up, lie down and stretch its limbs' (Brambell Report, 1965).

The alternative to stalls is some form of group housing. Group housing involves two types of social conflict, which have resulted in limited adoption of such systems. The first is the aggression associated with re-grouping unfamiliar animals. At the very minimum, 15-20% of any group will be replacement animals that are not familiar with the older sows in the herd. The resulting overt aggression may be short lived, but injuries are noticeable for several days, and the newcomers are often relegated to the least comfortable areas in the pen. The second type of aggression is associated with competition for feed, and may result in considerable variation in body condition within a pen. Group housing systems must be assessed on how well they control nutrient intake, as well as minimizing the two types of aggression.

Group Housing Systems

There are numerous group housing systems being used for gestating sows, but they generally fall within four general types. Floor feeding systems involve spreading a limited amount of feed over a large floor area. The spreading can be done by hand, but modern systems are generally mechanized. In such systems there is relatively poor control over individual feed intake, and high levels of aggression during feeding. The animals are often kept in small groups to minimize both re-grouping and feeding related aggression.

Another type of group housing provides a feeding site for each sow, and feed is dropped into these sites at a speed slightly slower than the animals can eat it. Each sow stands at a feeding site waiting for the feed, rather than attempting to take feed from another sow. These 'trickle' feeding systems control individual feed intake and feeding associated aggression fairly well, but animals must still be re-grouped and group size must be kept small.

A third type of group housing provides individual feeding stalls, and an open area for the non-feeding period. Feed intake is very well controlled, as is feeding-associated aggression. However, such a system still involves re-grouping aggression, requires a great deal of space, and still requires individual stalls.

A final type of group housing system involves the use of electronic sow feeders. In such a system each sow in the group wears an electronic identification tag and feeding is controlled by a computer and an electronic stall. When the sow enters the feeding stall she is identified by means of her tag, her records are checked on the computer, and her daily allotment of feed is provided to her. This system provides very good control over individual feed intake and prevents much of the feeding associated aggression, but still involves re-grouping fighting. The feeding and control equipment is more costly than in most other systems, but the computer can be used in other aspects of management.

Not all group housing systems are the same. Each achieves the goals of controlling individual feed intake and aggression to a different degree. In selecting a system for our new Elstow facility, we wanted to achieve very good control of feed intake with a system that could be applied to both medium and large sized farms. We choose the electronic sow feeder. This system also has the advantage that it can be modified to alleviate a number of common management tasks. For example, the feeding stations can be equipped with a sorting gate that will separate sows when they need to be pregnancy checked or moved to the farrowing room. The system can also be used to detect females as they come into estrous by monitoring their presence near a teaser boar pen.

Electronic feeding systems can be operated with relatively small groups of 30-50 sows on a single feeder, or with several hundred animals fed from several feeders within a single pen. We have chosen to conduct our first study examining two management styles using small groups, approximately one week's breeding.

The first management strategy is to minimize the introduction of new animals into a group by keeping each weekly breeding in one pen. This 'static' system still requires that replacement animals be added each cycle, and as a result the size of animals in the pen varies considerably.

The second strategy is to keep animals within a pen as uniform in size as possible. After breeding, the sows are sorted by size and placed into pens that contain animals of similar size from previous breedings. This system involves more re-grouping, but keeps smaller animals away from larger sows. We anticipate running this first comparison over 4 parities, or about two years.

Stall Housing:

Although stall housing appears very uniform, there are differences in the system among farms. Feed may be provided in individual feeders, or, more commonly, in a trough that runs in front of all of the sows. The trough system allows some feed to be pushed in front of adjacent sows and reduces the control of individual intake. Often trough systems have the feed drop tube pointed toward the middle of the stall to reduce this problem. Trough systems are also used to supply water rather than providing individual nipples or drinkers.

Another difference in stall systems is the size of the stall. In general, farms are equipped with only one size of stall, usually 22 or 24 inches (56 or 61 cm) wide. Some farms are equipped with even narrower stalls. The Code of Practice makes the logical recommendation that the size of stall should depend upon the size of the sow. We used the suggested sizes in the Code to develop a formula for width based on sow weight. We then estimated the demographics of our herd once we reach a stable population.

Based on this data, we have included stalls ranging from 22 to 28 inches (56 to 72 cm) in width, in proportions that should match the size of sows in our mature herd. For example, for each weekly breeding group we have four narrow stalls for small gilts, several stalls for second and third partity sows, a few less for 4th and 5th parity animals, and two 28 inch (72 cm) stalls for 6th parity animals. By allotting animals to stalls based on their size, we hope to reduce injuries and improve longevity.

Be Careful of General Comparisons

Too often we hear statements concerning 'group housing' and 'stalls' that imply that all such systems are the same. Group systems in particular are extremely different in how they control feed intake and manage aggression. It is important that we understand which particular group and stall systems are being compared. Gestation housing for sows is more complex than is often implied by generalizations.

Source: Prairie Swine Centre - November 2003