Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

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Author: search.filters.author.Corner-Thomas RASubject: search.filters.subject.Sheep

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    Where do all the ewes go? Ewe culling and mortality in 34 sheep flocks in New Zealand.
    (Taylor and Francis Group, 2024-10-17) Ridler AL; Corner-Thomas RA; Mote S; Morgan S; Kenyon PR; Flay KJ
    Aims To describe rates of and reasons for culling and mortality of ewes between breeding and mid-lactation on New Zealand sheep farms; to investigate associations of these variables with farm demographic variables; and to describe rates of and reasons for culling of ewes at weaning. Methods Participants were a convenience sample of 34 farms from across New Zealand. Demographic data were initially collected for each farm via a questionnaire administered in-person to the flock owner or manager. During approximately 8 months from breeding to mid-lactation, ewe tally, culling and mortality data were collected and used to calculate various parameters related to flock performance and to investigate associations. During the main ewe-culling event at weaning, ewe-culling data were collected from 29/34 flocks participating in the study. Results There was considerable variation between flocks, but the between-flock mean replacement percentage was 29.2 (SD 5.0)%. Overall, a between-flock mean of 10.5 (SD 4.6)% of ewes presented for breeding were culled or dead/missing by mid-lactation and thus did not rear any lambs. Additionally, from 27 flocks that reported data on ewes’ success at rearing lambs, a between-flock mean of 3.9 (SD 2.5)% of ewes that remained alive at mid-lactation failed to rear any lambs, resulting in an overall between-flock mean loss of 23.1 (SD 6.3) potential lambs per 100 ewes. Two-thirds of ewe mortalities between breeding and mid-lactation occurred during the lambing period. Model results showed flocks with higher pregnancy scanning percentages had lower rates of culling and mortality between breeding and mid-lactation. However, apart from farm contour, from breeding to mid-lactation there were no associations for culling and mortality with farm size, flock size, number of ewes per labour unit, whether ewe hoggets (7–9 months of age) were presented for breeding, or duration of the breeding period. A between-flock mean of 16.5 (SD 8.3)% of ewes present at weaning were culled, and among mixed-age ewes, the most common reasons for culling at this time were age, incisor teeth defects and udder defects. Conclusions To reduce unnecessary ewe culling and mortality, attention should be focused on maximising conception rates, ensuring judicious culling decisions, optimising body condition score, and identifying farm-specific causes of death over the lambing period to facilitate targeted intervention strategies. Clinical relevance Identifying why and when ewes exit flocks, and comparing it with the data presented here, will facilitate the development of flock-specific interventions to reduce ewe culling and mortality.
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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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    Ewe culling in New Zealand: an interview study of 38 farmers
    (Taylor and Francis Group, 2023-11-19) Ridler AL; Kenyon PR; Greer AW; Logan CM; Morgan S; Corner-Thomas RA
    Removal of ewes from a flock before the end of their productive life, sometimes described as ewe wastage, can potentially lead to reduced flock productivity. While the main reasons for culling ewes are largely known, their relative importance to New Zealand farmers and farmers’ rational behind their culling decisions are not. Therefore, this study involved semi-structured interviews with 38 sheep farmers from throughout New Zealand to explore their ewe culling decisions. Farmers consistently culled mixed-age and two-tooth ewes who failed to become pregnant or who had a vaginal prolapse. For other culling reasons, farmers’ use of them and their rationale for doing so was diverse and varied between farmers based on ewe age-group, severity, season, perceived economic consequences and farmers’ personal preference. This diversity indicates that there is scope for some farmers to carefully evaluate some of their culling decisions.
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    What Are Sheep Doing? Tri-Axial Accelerometer Sensor Data Identify the Diel Activity Pattern of Ewe Lambs on Pasture
    (MDPI (Basel, Switzerland), 2021-10) Ikurior SJ; Marquetoux N; Leu ST; Corner-Thomas RA; Scott I; Pomroy WE
    Monitoring activity patterns of animals offers the opportunity to assess individual health and welfare in support of precision livestock farming. The purpose of this study was to use a triaxial accelerometer sensor to determine the diel activity of sheep on pasture. Six Perendale ewe lambs, each fitted with a neck collar mounting a triaxial accelerometer, were filmed during targeted periods of sheep activities: grazing, lying, walking, and standing. The corresponding acceleration data were fitted using a Random Forest algorithm to classify activity (=classifier). This classifier was then applied to accelerometer data from an additional 10 ewe lambs to determine their activity budgets. Each of these was fitted with a neck collar mounting an accelerometer as well as two additional accelerometers placed on a head halter and a body harness over the shoulders of the animal. These were monitored continuously for three days. A classification accuracy of 89.6% was achieved for the grazing, walking and resting activities (i.e., a new class combining lying and standing activity). Triaxial accelerometer data showed that sheep spent 64% (95% CI 55% to 74%) of daylight time grazing, with grazing at night reduced to 14% (95% CI 8% to 20%). Similar activity budgets were achieved from the halter mounted sensors, but not those on a body harness. These results are consistent with previous studies directly observing daily activity of pasture-based sheep and can be applied in a variety of contexts to investigate animal health and welfare metrics e.g., to better understand the impact that young sheep can suffer when carrying even modest burdens of parasitic nematodes.