Dominant sows have a distinct advantage in terms of feed intake and weight gain in floor feeding systems (Brouns and Edwards, 1994). Subordinate sows that are also usually younger and lighter, will fall behind in body condition and may have to be removed. A ‘relief’ rate of 15% is common when floor feeding. Social management is the primary means of evening out feed intake in floor feeding systems. In non-competitive systems, such as finisher pigs, there is some advantage to having a significant variation in the size of the pigs. This is because the social system actually operates better with some variation, i.e. if there are many individuals of the same competitive status; there will be increased aggression until a hierarchy is established. The opposite is the case when dealing with competitive situations, especially situations of competition over feed. To ensure the most even feed intake among a group of sows, the sows should be as similar as possible, making them equally competitive. This will take the form of sorting sows by parity, weight and body condition. The result is a group of sows having the same feed requirement, and the same potential to compete for it. This sorting within a breeding cohort obviously results in smaller group sizes.
In order to have sows enter the system with similar body condition, it is advantageous to house them in stalls until confirmed pregnant (normally 35 days post-breeding) and feed them to achieve similar backfat levels by that time. Use of such ‘breeding and implantation’ stalls is particularly important for floor feeding systems as excessive competition and poor feed intake during this critical phase can affect reproduction (Spoolder et al., 2009).
Keys to successful floor feeding
- Sort sows by parity, size and body condition.
- Use the time in breeding/implantation stalls to even out body condition.
- Spread feed as evenly as possible.
- Use dividers within the pen.
- Remove sows that fall behind.
In terms of physical management, it is possible to use some dividers within the pen to create several feeding sites. This is only possible with larger groups. In general, the feed should be spread about as much as possible (multiple drop sites), to prevent a sow from defending a large drop of feed.
Using bulky, high fi bre feed will extend the feeding time and reduce the incidence of stereotypic behaviours, but may contribute to more aggression. Similarly, feeding on a straw floor will extend feeding periods and increase aggression (Whittaker et al. 1999).Feeding a bulky diet ad-lib allows the subordinate sows to avoid peak feeding times and consume normal levels of feed (Brouns and Edwards, 1994), but it must be bulky enough to limit total energy intake.
Large Group Floor Feeding
Several farms in Ontario have adopted a novel floor feeding system that differs from most feeding systems in three ways: the groups are large, and may include sows of different parities; the pen has a number of partial divisions that provide some separation of the multiple feeding sites; and, the feed is dropped in several (typically 6) drops per day, spaced 30 to 60 minutes apart. Large, non-uniform groups reduce social tension in finisher pigs, but are not generally advocated for in competitive systems, such as gestating sows. The barriers provide sows with some physical protection, as seen in short-stall systems, but several sows still eat from the same feed drop. Frequent feed drops that allow subordinate animals to eat from the later drops as the dominant sows feel satiated from eating from the first may be the key to the system.
Although several farms have adopted this system, it has not been studied in comparative tests. As with any floor feeding system, some sows have to be removed. At least one producer does not include gilts with the sows. The system as a whole, and multiple feed drops in particular, should be studied before being widely adopted. However, it illustrates that floor feeding can be managed in many different ways.