Friedrich, L., Krieter, J., Kemper, N. et al. 2020. Frothy saliva—A novel indicator to assess stereotypies in sows? Applied Animal Behaviour Science 222, 104897.

The present study aimed at introducing a reliable and more feasible indicator to evaluate stereotypies in sows in comparison with the ‘Welfare Quality® animal welfare assessment protocol for sows and piglets’. Therefore, the indicators for the assessment of stereotypies of the Welfare Quality® protocol for sows and piglets as the gold standard (sham chewing, tongue rolling, teeth grinding, bar, drinker, trough biting and floor licking) were tested in relation to the potential indicator ‘frothy saliva’ in an on-farm study on farrowing farms. The analysis included the correlation between indicators, their interobserver agreement and test-retest reliability. Therefore, Spearman’s rank correlation coefficient (RS), intraclass correlation coefficient (ICC), smallest detectable change (SDC) and limits of agreement (LoA) were used. As results, the potential indicator ‘frothy saliva’ showed an acceptable correlation with the most observed indicator sham chewing (RS 0.42), which was in turn correlated to the indicator tongue rolling (RS 0.35). ‘Frothy saliva’ showed similar interobserver agreement as the indicators for the assessment of stereotypies, e.g. ‘frothy saliva’ (RS 0.90 ICC 0.93 SDC 0.16 LoA [−0.18;0.14]) and sham chewing (RS 0.96 ICC 0.94 SDC 0.11 LoA [−0.08;0.13]). Concerning its test-retest reliability, the results showed that the potential indicator ‘frothy saliva’ can be used to differentiate between farms (RS 0.61-0.87 ICC 0.74-0.91 SDC 0.20-0.35 LoA [−0.16;0.24]–[−0.46;0.25]), which matched the results of the indicators for the assessment of stereotypies, e.g. sham chewing (RS 0.81-0.93 ICC 0.80–0.91 SDC 0.16-0.23 LoA [−0.22;0.10]–[−0.24;0.21]). Sensitivity, specificity and regarding result parameters confirmed the usefulness of the potential indicator ‘frothy saliva’ on-farm (sensitivity 0.86, specificity 0.62, positive likelihood ratio 2.26, negative likelihood ratio 0.23). However, organic enrichment material can be a confounding factor. So does the currently still unknown relationship between ‘frothy saliva’ and non-stereotypic foraging or eating activities of sows. Besides that, the potential indicator ‘frothy saliva’ proved to be as reliable as the indicators for the assessment of stereotypies and demonstrated higher feasibility. Hence, the use of the potential indicator ‘frothy saliva’ is recommended to assess stereotypies in sows. Thereby, it could contribute to an improvement of the Welfare Quality® protocol for sows and piglets.