Validation of an automatic system to detect position changes in puerperal sows

Piglet crushing by the sow is one of the main causes of piglet mortality during the first 48 h after birth. The frequency of position changes may be partially related to the pain caused by farrowing. The aim of this study was to develop and validate an automatic system to register position changes between standing and lying position in farrowing sows. Forty hybrid (Large White × Landrace) sows from first to seventh parity housed in individual farrowing crates were used. Position changes were automatically recorded using Standing Lying Sensors (SLS), which consisted of a photoelectric cell located near the forelegs of each sow at a height of 72 cm from the floor and connected to a laptop for continuous recording. Sow behaviour was registered continuously for 3 days before and 3 days after farrowing. To validate the SLS, data from a total of 135 animal-days obtained through video recordings were compared with data obtained from SLS using Spearman correlations. When total time lying down versus total time standing or sitting was considered, a correlation of 0.85 was obtained. Using a 55 s filter that converted lying bouts of less than 55 s into standing behaviour and vice versa, a correlation of 0.91 was obtained for the frequency of position changes. Moreover, the SLS presented a 64.13% of sensitivity and an 87.97% of specificity. SLS could not differentiate between standing and sitting position. However, according to video recordings, changes from sitting to standing accounted for 14.40% of the total activity and changes from standing to sitting – which are position changes potentially dangerous to the piglets – accounted for only 0.31% of the total activity. One day before farrowing and on the day of farrowing, sows changed position more often and spent more time standing up or in sitting position than on the other days of the study (P < 0.0001 and P < 0.05, respectively). The peak in sow postural changes was during 0–6 h prior to the onset of farrowing (P < 0.0001). The frequency of position changes and the total time in each position were not affected by parity. The SLS appears to be a reliable method to record position changes in farrowing sows and could be used to assess the relationship between management and husbandry factors, sow behaviour and piglet crushing.