Candidate: Angus, Sofie

Monitoring changes in liveweight using precision technology as an indicator of parasite burden in ewes

Abstract

Abstract
While walk-over-weighing (WoW) stations have been validated to collect subtle daily liveweight changes in sheep, there have been no reports relating these weight changes with animal reproductive, productive or health measures. This study was designed to investigate the ability of WoW derived liveweight data to indicate individual animal internal parasite burdens. Poll Dorset ewes (n = 67) were randomly selected based on the number of foetuses they carried (singleton, twin, or triplet). Weight data was analysed in two trials: mid-late gestation (Trial 1), and late gestation to weaning (Trial 2). Faecal egg counts (FEC) were taken at the beginning of Trial 1, and the end of Trial 2. In Trial 1, daily liveweight change was found to be significantly (p < 0.05) related to FEC, reproductive effort and the interaction between liveweight and FEC of triplet carrying ewes. There was no significant (p < 0.05) relationship between liveweight and FEC, or reproductive effort, in Trial 2. The lack of consistency in results within and between trials indicated liveweight status can be influenced by more than pregnancy and parasite burden. It is likely that animal management, fluctuations in feed quality, environment, and ewe physiology played a meaningful role in mitigating, or intensifying, the impacts of parasites in sheep. Therefore, remotely collected liveweight data is not the most appropriate variable to monitor internal parasite challenge in pregnant ewes due to the complexity of parasite interactions with climate, management, and individual animal physiology; variables that should be included in future studies.