Table 3.
Interaction with different types of enrichment compared within one study.
| Enrichment | Fold Change from Least Used Enrichment 1 | % of Pig’s Time Spent in Interaction 2 | % Time Enrichment in Use | % of Minutes Including Interaction | Stage | Ref. |
|---|---|---|---|---|---|---|
| Maize silage | 1.23 | 23 | - | - | G-F | [64] |
| Suspended garlic scented rope Suspended rope |
4.00 |
17 4 |
- |
- |
W |
[71] |
| Peat (6 cm deep layer, 2.8 m2) | - | 15 | - | - | W + G-F | [72] |
| Bark | 20.00 | 14 | - | - | G-F | [66] |
| Branches | 1.00 | 0.7 | - | - | ||
| Rope and wood provided continuously | 3.62 | 13 | - | - | W | [65] |
| Weekly alternation between 1: wood and 2: rope | 2.97 | 11 | - | - | ||
| Rope suspended from a wall bracket | 2.76 | 10 | - | - | ||
| Weekly alternation between 1: rope and 2: wood | 2.51 | 9 | - | - | ||
| Wood block placed on floor (washed daily) | 1.00 | 4 | - | - | ||
| Compost in overhead rack | 1.63 | 13 | - | - | G-F | [35] |
| Empty overhead rack | 1.00 | 8 | - | - | ||
| Sucrose solution tube (energy restricted pigs) | 3.85 | 7 | - | - | G-F | [77] |
| Saccharin solution tube (energy restricted pigs) | 1.85 | 4 | - | - | ||
| Water tube (energy restricted pigs) | 1.00 | 2 | - | - | ||
| Turf | 2.33 | 4 | - | - | W | [74] |
| Peat filled tray | 1.00 | 2 | - | - | ||
| Suspended rope | 11.57 | 4 | - | - | W | [74] |
| Artificial dog bones | 4.73 | 1 | - | - | ||
| Suspended chains | 1.00 | 0.3 | - | - | ||
| Suspended hard wood (in larger high density groups) | - | 4 | - | - | G-F | [14] |
| Suspended hard wood (in smaller low density groups) | - | 4 | - | - | G-F | |
| Sucrose solution tube (non-energy restricted pigs) | 1.38 | 3 | - | - | G-F | [77] |
| Saccharin solution tube (non-energy restricted pigs) | 1.08 | 2 | - | - | ||
| Water tube (non-energy restricted pigs) | 1.00 | 2 | - | - | ||
| 4× cross of flexible plastic piping suspended on chain | 1.56 | 1.4 | - | - | [75] | |
| 1× cross of flexible plastic piping suspended on chain | 1.00 | 0.9 | - | - | ||
| Silage of oats, vetch and lupine roughage box | 6.37 | 1.2 | - | - | G-F | [43] |
| Chopped fodder beet in roughage box | 2.17 | 0.4 | - | - | ||
| Whole-crop silage of clover and grass in roughage box | 1.97 | 0.4 | - | - | ||
| Whole-crop silage of barley and peas in roughage box | 1.75 | 0.3 | - | - | ||
| Green grass meal in roughage box | 1.33 | 0.3 | - | - | ||
| Hay of grass and clover in roughage box | 1.06 | 0.2 | - | - | ||
| Empty roughage box | 1.00 | 0.2 | - | - | ||
| Horizontal cylinder of compressed wood shavings | 1.58 | 0.8 | - | - | W | [40] |
| Suspended metal chain | 1.08 | 0.5 | - | - | ||
| Pressed feed block, fixed to frame but rotatable | 1.00 | 0.5 | - | - | ||
| Suspended metal chain | 1.16 | 0.7 | - | - | W | [40] |
| Horizontal frame-mounted wooden post | 1.00 | 0.6 | - | - | ||
| 4× wooden beams in racks, could be moved vertically | 3.14 | 0.6 | - | - | G-F | [57] |
| 2× wooden beams in racks, could be moved vertically | 1.00 | 0.2 | - | - | ||
| Flavoured bar in a dispenser with drinker and trough | 8.20 | 0.4 | - | - | G-F | [68] |
| Suspended looped chain | 1.00 | 0.1 | - | - | ||
| Multiple suspended wooden sticks | 2.57 | 0.2 | - | - | G-F | [70] |
| Wooden stick fixed to wall, could be moved vertically | 1.43 | 0.1 | - | - | ||
| Suspended wooden stick | 1.00 | 0.1 | - | - | ||
| Wooden block, elevated on one side by a plastic ring | 9.29 | - | 65 | - | G-F | [78] |
| Ropes fixed to chains movable within an elevated pipe | 5.71 | - | 40 | - | ||
| Triangular assembly of spring-mounted plastic balls | 4.71 | - | 33 | - | ||
| Suspended scented plastic ring | 2.86 | - | 20 | - | ||
| Plastic sticks fixed to a suspended central cone | 2.29 | - | 16 | - | ||
| Suspended disc with plastic strips and chains | 1.57 | - | 11 | - | ||
| Rigid plastic ball, loose on floor | 1.00 | - | 7 | - | ||
| Suspended knotted rope | 2.29 | - | 32 | - | G-F | [78] |
| Triangular assembly of spring-mounted plastic balls | 1.79 | - | 25 | - | ||
| Rigid plastic balls, loose on floor | 1.21 | - | 17 | - | ||
| Plastic sticks fixed to suspended central cones | 1.00 | - | 14 | - | ||
| Rubber dog toy suspended on an elastic cord | 4.46 | - | 31 | - | W | [12] |
| Knotted rope suspended on an elastic cord | 1.71 | - | 12 | - | ||
| Rubber hose suspended on an elastic cord | 1.29 | - | 9 | - | ||
| Metal chain suspended on an elastic cord | 1.00 | - | 7 | - | ||
| Rope (suspended horizontally or vertically) | 3.59 | - | 8 | - | G-F | [81] |
| Metal pipe (suspended horizontally or vertically) | 1.41 | - | 3 | - | ||
| Wood (suspended horizontally or vertically) | 1.32 | - | 3 | - | ||
| Chain (suspended horizontally or vertically) | 1.00 | - | 2 | - | ||
| Wall mounted metal chain with rubber hose around it | 2.00 | - | - | 8 | W + | [82] |
| Rubber hose, placed on floor | 1.75 | - | - | 7 | G-F | |
| Rope, suspended from spring | 1.75 | - | - | 7 | ||
| Hard plastic ball with stones inside, loose on the floor | 1.00 | - | - | 4 | ||
| Chopped myscanthus, provided on floor | 1.20 | - | - | 6 | G-F | [69] |
| Bark compost in a floor level trough | 1.00 | - | - | 5 | ||
| Feed dispenser | 3.00 | - | - | - | G-F | [60] |
| Plastic sticks fixed to a suspended central plastic cone | 2.40 | - | - | - | ||
| Non-functioning liquid dispenser | 1.00 | - | - | - | ||
| Rope suspended from wall-mounted chain | 1.70 | - | - | - | W + | [36] |
| Purple ribbon suspended from wall-mounted chain | 1.50 | - | - | - | G-F | |
| Yellow ribbon suspended from wall-mounted chain | 1.40 | - | - | - | ||
| Grey hosepipe suspended from wall-mounted chain | 1.25 | - | - | - | ||
| Rubber bar suspended from wall-mounted chain | 1.20 | - | - | - | ||
| Rubber ball suspended from wall-mounted chain | 1.10 | - | - | - | ||
| Yellow hosepipe suspended from wall-mounted chain | 1.00 | - | - | - | ||
| Combination of all materials below | 6.20 | - | - | - | G-F | [32] |
| Suspended plastic pipes + single chain | 5.80 | - | - | - | ||
| Suspended freshly cut wood + single chain | 5.40 | - | - | - | ||
| Suspended branched chains end on floor + single chain | 1.20 | - | - | - | ||
| Suspended single chain | 1.00 | - | - | - |
Within the category of output variable, studies have been ordered according to the level of interaction with the most used enrichment; 1 Fold change: level of interaction with an enrichment / level of interaction with the least used enrichment in that study. Note that the type of least used enrichment varies between studies, limiting the validity of comparing fold changes across studies; 2 % of time per pig. Depending on the original data this percentage could be based on continuous observation of focal animals or scan sampling of a known number of individuals (but not on frequencies of behaviour obtained from continuous observations, or the percentage of scans in which the behaviour was performed by an unspecified number of individuals); W: Weaners, G-F: Growers/fatteners.