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    Worms and welfare: Behavioural and physiological changes associated with gastrointestinal nematode parasitism in lambs.
    (Elsevier B.V., 2023-10-27) Hempstead MN; Waghorn TS; Gibson MJ; Sauermann CW; Ross AB; Cave VM; Sutherland MA; Marquetoux N; Hannaford R; Corner-Thomas RA; Sutherland IA
    Parasitism with gastrointestinal nematodes (GIN) is a worldwide issue impacting negatively on animal production, health, and welfare. Therefore, early diagnostic signs of parasitism are required to allow for timely interventions. The objective of this study was to evaluate the behavioural and physiological changes in lambs associated with GIN infection. We used 30, 8-month-old Romney-cross wethers, that were administered anthelmintics until faecal egg counts (FEC) were zero and housed in an indoor facility. The study lasted 9 weeks, which comprised a 3-week pre-treatment, and a 6-week treatment phase. Lambs were randomly assigned to one of two treatments (n = 15/treatment) trickle-dosed with: 1) 1500 infective third stage larvae (L3) three days/week for 6 weeks (27,000 total L3; challenged), or 2) water 3 days/week for 6 weeks (control). Within each pen there were 5 pairs of lambs (balanced for liveweight), with each pair comprising a challenged and control lamb. Blood, faecal, and saliva samples were collected 1 week pre-treatment and weekly for 6 weeks of treatment. Behaviour was observed (e.g., feeding, lying, standing) from video-camera recordings using scan sampling every 5 min for 8 h, 1 day pre-treatment and on the day immediately prior to physiological sampling across the 6-week treatment phase (7 days in total). Accelerometers were attached to each lamb to continuously monitor behaviour from 3 weeks pre-treatment and for the remainder of the study. Liveweight, body condition, faecal soiling and faecal consistency scoring were performed weekly as was lipidomic analysis of plasma samples. From week 2 of treatment, challenged lambs spent less time feeding and more time lying than control lambs until week 5 of treatment (P ≤ 0.01). At week 3 of treatment, elevated lipids (mainly triglycerides and phospholipids), loose faeces and faecal soiling around the anus were observed in challenged lambs compared with controls (P ≤ 0.05). From week 4 of treatment, FEC were elevated in the challenged compared to control lambs (P ≤ 0.05). There was also lower liveweight gain at 4 and 5 weeks of treatment in the challenged lambs compared with control lambs (P ≤ 0.05). These results show a clear timeline of changes in behaviour (e.g., feeding and lying), lipids such as triglycerides, and digestive function (e.g., faecal soiling) suggestive of GIN subclinical disease, which show promise for use in future studies on early identification of subclinical GIN parasitism in lambs.
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    Epidemiological studies of parasitism in sheep and reproduction in horses : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies (Epidemiology) at Massey University
    (Massey University, 1997) Macchi, Chiara
    Anthelmintic resistance is a well-recognised problem for control of nemotodes in sheep in most countries of the world. The climatic conditions in New Zealand are particularly favourable to the survival and development of gastrointestinal nemo=atodes. As a consequence, gastrointestinal parasitism is a major impediment to profitable sheep raising in New Zealand. A random postal survey of 300 sheep farmers in the southern North Island region of Manawatu was conducted with the purpose of examining current farming and drenching practices and investigating possible risk factors in the development of anthelmintic resistance. The results of this study, reported in Chapter 2, revealed a high degree of awareness and concern about the problem of resistance, but also a lack of understanding on how grazing management strategies should be combined in order to achieve integrated control over gastrointestinal nematodes while minimising the use of anthelmintic drugs. Only 31% of respondents had performed at least one drench test on their property. Amond testing farms, prevalence of resistance approached 70% and involved benzimidazole products in all but one case. Subsequently, a trial was undertaken to investigate the economic consequences of anthelmintic resistance in growing lambs on commercial farms (Chapters 3 and 4). Five farms with a history of resistance to benzimidazole drenches were selected. The effects of three treatment strategis on nematode egg counts, bodyweight gains and susceptibility to diarrhoea were compared between groups of ewe lambs. Suppressively treated lambs performed significantly better than effectively treated lambs, which in turn performed better than ineffectively treated lambs. However, a partial budgeting analysis carried out by means of a stochastic simulation model (Chapter 4) indicated that effective treatment yielded the highest net returns. The model also showed that the range of possible outcomes oscillated substantially around the mean, reflecting the degree of uncertainty about the outcome on any single farm due to variation between farms. Chapter 5 describes a study which was carried out with the objective of evaluating two management strategies for breeding mares after foaling. Mares were examined on day 7-9 postpartum by palpation and ultrasound. Pregnancy rates, pregnancy loss rates and time from foaling to conception in two groups were compared. The statistical power of the study as determined by power analysis, was insufficient for the observed differences to reach statistical significance.