We tested sow preferences for lying down alongside a plain wall, a sloping wall or a wall with a farrowing rail. Beforehand, we tested preferences for three sloping wall designs (plain, curved and multiple bars) in order to use the preferred one in the later choice experiment. In both experiments, 4 × 6 pregnant second–seventh parity individually housed sows were used over a 3-day training and a 4-day testing period. In both experiments, the three types of walls were balanced on position in the pen.
In both tests, the sows predominantly lay down alongside the walls (on average, 80 ± 4 and 86 ± 3%of lying down events, respectively). In the test of the three sloping wall designs, the sows had no significant preferences for wall designs. For practical reasons the plain sloping wall was used in the subsequent test. Here, there was a significant effect of wall type (on average, 16 ± 5%of lying down events alongside the wall with the farrowing rail, 48 ± 8%alongside the plain wall and 36 ± 8%alongside the plain sloping wall (P < 0.025)). The sows lay down alongside the wall with the farrowing rail less than alongside the plain or the plain sloping wall (P < 0.01), but the preference for the two latter wall types did not differ significantly. Irrespective of the wall type, the sows had a significant preference for the back wall of the pen (P < 0.001 in both experiments).
In conclusion, walls with farrowing rails appear to be less attractive to lie down against than other wall designs. Although farrowing rails provide piglets with escape zones they may not be optimal for piglet survival because they do not encourage the sow to lie down alongside a wall, rather than in the open. Moreover, they may not be optimal from a sow welfare perspective due to lack of support for the sow when lying down.