Legislation specifying group housing of pregnant sows comes into law in the European Union on January 1, 2013 and may follow in other regions, which forces pig producers to review their management methods. This should include a re-evaluation of the sow feeding system, because they can play a huge role in overcoming some of the problems that could arise in group-housed sows.
Particular attention must be paid to sow appetite – this needs to be satisfied, because if the sow feels hungry it could lead to several other health and welfare problems in group housing systems.
When sows are first introduced in a group, they fight to establish a dominance hierarchy. After a few days, the hierarchy is established and fighting stops, but in the meantime injuries, miscarriages and high stress levels can occur.
However, if sows feel satiated fewer behavioral problems are likely to occur. To achieve this, an appropriate amount of dietary fiber in their ration is required. Feed that is rich in fiber is eaten more slowly, which means the sow is busy eating for a longer period of time. Quantity and quality of the dietary fiber are important, because not all sources of fiber are of equal value.
Fiber-rich products should mycotoxin free and differentiated according to their swelling properties. Dried pulp or soy husks, for example, have a greater swelling and water holding capacity, which fills the stomach, compared with cereal products. The fiber grind is also important – a coarser grind is more satisfying for the sow. Fine grinding destroys the structure of the feed component and the sow will be less satisfied. Furthermore, the cost of fiber must be considered.
Studies show that sows fed ad-lib produce more piglets per sow per year and a fewer number of sows return to oestrus, compared with those with restricted feeding, as shown in Table 1 . However, they also consume considerably more feed so it is important to optimize the energy value.
Fermentation of feed to energy in the colon of pregnant sows is more efficient than in finishing pigs. Fermentable carbohydrates in the colon are responsible for the feeling of satiation. Fermentable carbohydrates include digestive fiber plus digestive carbohydrates excluding starch or sugar. Feedstuffs with a high starch content increase the insulin level quickly, but the increase is not sustained for long and subsides just as quickly, leading to a renewed feeling of hunger. Other feeds such as dried pulp, with high concentrations of fermentable carbohydrates are a better option as they maintain stable blood sugar levels for longer.
Sow feeding equipment
Sow feeding regime during gestation is crucial and it should help prevent them from building up too many body reserves. Pregnant sows must not be overfed and become over-conditioned, as this can lead to farrowing problems and a loss of appetite in early lactation.
Ideally, gestating sows should be fed individually, following a ration that is based on their individual body condition. Two possibilities are free-access stalls and feeding on demand. Table 2 compares sow rations in the two systems. Free-access stalls can work well, as the diet can be tailored to the sow’s requirements and aggression during feeding is reduced compared with more restricted feeding systems. This system is easy to control and it is possible to create a flatter feeding curve. Ideally, sows should be divided into four groups depending on their condition, for example, gilts, thin, normal and fat sows. Feeding on demand can lead to more aggression and bickering. Individual feed intake, however, is easy to control and it is possible to use different feeding curves based on sow condition.
To help minimize fighting among sows, associated with on demand feeding the feed should include more fermentable carbohydrates and a higher water-holding capacity. This increases the sows’ feeling of satiation, while maintaining the same energy value and digestible lysine concentration.
To achieve satiation, the fermentable carbohydrate content of the ration should be increased to around 9.3 percent compared with 7.5 percent in free-access stalls, with sugar beet pulp and sunflower meal providing the main sources of fiber.
It must be mentioned at this point that good quality fiber doesn’t come cheap. Therefore, with this example, the cost of the ration increases by 3 percent. However, if this method of ration optimization successfully keeps the sows calm during on demand feeding and reduces aggression, the additional expense can be justified.
Sow diet, leg health
Sows housed in groups need excellent leg conformation, which should be considered when selecting stock. Over-conditioned sows often have more leg problems, because the weight does not match the leg conformation.
A correct balance of minerals and vitamins in the diet plays a part in maintaining good overall sow conformation. A magnesium supplement, for instance, can be very beneficial for bones. Omega-3-fatty acids, vitamin D3 and biotin help to maintain foot health, with zinc supplements also playing a valuable role.
The legs and feet of group-housed sows must be continually monitored to ensure that group housing has no detrimental effects on the animals’ well-being. Lameness should be identified quickly and dealt with appropriately.
Ultimately, the success of group housing is determined by the right feeding ration, suitable housing system and genetics. There are advantages of forward planning the feeding regime before group housing of sows to help avoid problems and a drop in performance.