Behavioural assessment of sheep is sensitive to level of gastrointestinal parasite infection

Abstract

Qualitative behavioural assessment (QBA) was applied to investigate the expressive behaviour of sheep with varying intestinal parasite burdens over two experiments. The expressive behaviour of sheep naturally infected with intestinal parasites was assessed from video footage collected in the paddock, and assessments were compared pre- and post-treatment with anthelmintic drench. The first experiment assessed sheep with a range of parasite burdens (n = 28), and the second compared sheep that expressed clinical symptoms of parasitism (Anaemic, n = 5) with those that did not (Non-anaemic, n = 5). Behavioural expression scores were validated against individual clinical evaluations (faecal egg counts – FEC, faecal consistency and anaemia scores), production parameters (body mass and body condition score), and quantitative locomotive measures (walking speed and return order to paddock). Twenty-two observers scored 28 video clips using QBA in experiment 1, and in the second experiment, 35 observers scored 20 video clips that depicted the 10 focal sheep pre- and post-treatment. QBA scores were analysed using Generalised Procrustes Analysis (GPA), and sheep scores on the main GPA dimensions were evaluated in relation to parasite burden using Spearman Rank correlations and repeated-measures ANOVA for experiment 1 and 2, respectively. In both experiments, observers reached significant (P < 0.001) consensus in their assessment of the behavioural expression of sheep. In experiment 1, sheep with higher FEC had lower anaemia scores (indicative of anaemia), poor body condition, lower body mass, walked slower, ranked lower in return order, and were scored by observers as more docile/at ease, and more assertive/motivated on GPA dimensions 1 and 3, respectively (P < 0.05). In experiment 2, observers scored Anaemic sheep as significantly more unsettled/apprehensive compared to Non-anaemic sheep on GPA dimension 1 (P < 0.05). In addition, observers consistently scored Non-anaemic sheep as more bright/observant following treatment on dimension 2 (P < 0.001). On dimension 3, all animals were scored by observers as less depressed/suspicious post-treatment (P < 0.05). An increase in average walking speed across all sheep was also identified post-treatment (P < 0.05). We conclude that under the conditions tested, QBA could provide information on the behavioural expression of sheep related to varying parasite burdens and the impact of treatment. The data presented herein offers proof of concept that assessments of behavioural expression could aid producers in the monitoring and management of parasitised sheep on-farm in terms of identification of individuals for treatment, and efficacy of anthelmintic treatment.