As an alternative to floor feeding, producers should consider the use of feeding stalls in order to provide protection during eating. Recalling the earlier statement on dominance, we note that dominant animals will exert themselves when resources are both limited and defendable. Defendable refers to the ability of the dominant animal to control more than their share of the resource. Shoulder stalls prevent the dominant animal from monopolizing the feed by allowing the subordinate animals to defend a small portion of the total feed available, that is, their share of the feed. However, with enough eff ort dominant sows will be able to force a subordinate out of a shoulder stall and thereby obtain more feed.
Shoulder stalls should make use of the social management techniques outlined for floor feeding (e.g. sorting by size and body condition). However, these systems also use physical methods to interfere with dominant sows attempting to displace subordinates from their feed. Shoulder stall systems use feed troughs so that the feed can be delivered and limited to a defined area. These troughs are divided so that individual allotments of feed are dropped into each division. Stalls are added to these divisions to provide protection to each sow as she eats. The longer the stalls, which typically vary from shoulder length to full body length, the less aggression and more even intake of feed (Barnett et al., 1992, Andersson et al., 1999). Floor feeding gives a distinct advantage to the dominant sow. Partial stalls reduce this advantage and allow the subordinate animals to spend more time eating and achieve a higher intake.
Impact of Stall Length
Shorter stalls, such as those that only extend back to the animal’s shoulders, will not fully protect a subordinate animal. In systems with these stalls, it is common to see cuts and scratches on the sides of the lower ranking individuals where the dominant sows have attempted to displace them from the feed trough. Longer stalls will provide more protection, but some displacement may still occur. If longer stalls are better, then why would a producer use short stalls? It is a balance between protection during feeding and the amount of space the system requires. Group housed sows should have a sufficient amount of free space (outside of the stall) to move about freely. If a producer uses long stalls, additional space is necessary behind the stalls to provide this loafing area. Longer stalls also represent a greater capital expense, in addition to the increased floor space.
Are there other means to reduce aggression and displacements among sows in shoulder stall systems? There appear to be at least two: increasing the eating speed of the sows will reduce the time required to consume their feed and decrease feeding associated aggression (Andersson et al., 1999). One of the easiest ways to increase the speed of eating is to provide wet feed, either as a slurry, or by adding water in the feed trough. By eating faster, the subordinate sows are nearly finished their feed by the time the dominant sow is able to displace them from the stall. Although reducing aggression and displacements, the rapid eating may increase other problems associated with short meals, such as increased stereotypic behaviour.
The second method used to reduce displacements from short stalls is trickle feeding. Typically all of the feed for a sow is dropped into the trough at the same time. Faster eating sows consume their feed and then attempt to displace slower eating animals and steal their remaining feed. Trickle feeding meters the feed into the trough over an extended time, typically 30 minutes or so (Hulbert and McGlone, 2006). Ideally, the rate of feed supply should be as slow as or slower than the eating speed of the slowest eating animal. If a faster eating animal decides to leave its stall to displace a slower eating one, no feed would have accumulated in the slower one’s trough. The advantage to displacing another sow is lost. However, if the drop rate is the same as the eating speed of the faster eating sow, the slower eating animals will accumulate feed in their trough space and be vulnerable to attack from other sows. Trickle feeding has received mixed reviews. If it is well managed it may well reduce feeding associated aggression among sows. However, this is not always the case (Hulbert and McGlone, 2006).
Two Types of Problems
If the performance of your sows in a competitive feeding system is below your expectations, it is easy to blame the feeding system. However, feeding system design is not always the problem. Two types of stressors can affect animals in groups: competitive and general. To determine which stressor is most likely within your system it is important to determine the demographics of the problem. If the problem affects younger, smaller animals’ more than larger, older animals, it is likely a competitive issue. A common problem in competitive feeding systems is the fat sow/ thin sow syndrome, in which smaller sows get thinner and larger sows get fatter. In this case you should attempt to reduce competition during feeding. However, if your problem is as common among larger sows as it is among smaller ones, then it is likely a general stressor that affects all of the pigs similarly. Examples of general stressors would include high temperatures, poor flooring, and poor air quality or space restriction. The solution to these problems is quite different to that of a competition problem. In some instances, the problem may involve both general and competitive stress. For example, if poor flooring results in 10% of the sows becoming lame, evenly distributed across all sizes, the smaller lame sows may be at a greater disadvantage when trying to compete for feed. If you can identify that lameness was the initial problem, and improve the flooring, you will be more successful in correcting the subsequent problem caused by competition.
Keys to successful shoulder stall systems
- Longer stalls will reduce aggression
- Wet diets take less time to consume and reduce aggression
- Trickle feeding prevents the accumulation of feed in front of slow-eating sows
Choosing Between Floor Feeding and Shoulder Stalls
Both systems are less expensive than the non-competitive gated stall and ESF feeding systems. Producers who use these systems are looking for a less expensive system and are prepared to accept more aggression and to give up some control over feed intake. If the producer is prepared to place a great deal of emphasis on social management, then they are more likely to choose floor feeding. It is the least expensive of all of the systems. However, if they fi nd social management difficult, they may want to spend more and provide their animals with the partial protection of short, shoulder stalls. In larger operations, the decision may be based on the confidence the operator has in the ability of their staff to socially manage the animals. As in every system, better management will result in better production.