Risk factors for Merino ewe mortality on the Northern Tablelands of New South Wales, Australia

Kelly, Gareth Andrew; Kahn, Lewis; Walkden‐Brown, Stephen W.

doi:10.1111/avj.12145

Cited by 11 publications

(8 citation statements)

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“…This agrees with New Zealand results in which poor BCS was reported as a common cause of ewe mortality [18]. These results are also consistent with international data in which mortality rates were increased in poor-BCS ewes [6,12]. It is possible that for some of these poor-BCS ewes, the poor BCS is a proxy for other diseases [5,18,19]; therefore, further investigation into the underlying causes of poor BCS in commercial ewes is required.…”

Section: Discussionsupporting

confidence: 90%

“…Annual dead/missing incidence, considered a proxy for mortality rates, ranged from 3.5 to 20.8% in Years 1-5 (Table 5). This is comparable to previously reported annual on-farm mortality rates of 2.8-27.0% in New Zealand [15,16,18,19], 2.7-22.0% in Australian extensive flocks [11,12,20,33], and 3.0-10.0% for flocks based in the United Kingdom and Ireland [2,[21][22][23]. However, in this study, mortality incidences in Year 6 were between 7.0 and 40.2% (Table 5).…”

Section: Discussionsupporting

confidence: 87%

“…It is important to note variability and potential inaccuracy in recording wastage rates in extensively managed commercial flocks [2,5]. This is likely due to farm topography and flock size, farm management structure, degree of human contact with individual ewes within the flock, and perceived likelihood of wastage [11][12][13]. In addition, in extensive flocks, ewes are typically managed as a flock, with management decisions based on overall flock needs rather than individual animal needs per se.…”

Section: Introductionmentioning

confidence: 99%

“…The relationship between BCS and various reproductive traits has been well documented, with the optimum BCS for a ewe from a production perspective suggested to be in the range of 2.5-3.5 at breeding (see review [31]). In addition, poor ewe BCS, particularly ewes with a BCS < 2.5, appears to be associated with increased ewe wastage, both in New Zealand and internationally [6,12,18]. For commercial farmers, it would be optimal if they were able to identify ewes that are likely to be poor performing or at greater risk of wastage, prior to breeding.…”

Section: Introductionmentioning

confidence: 99%

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Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS

Flay

Ridler

Compton

et al. 2021

Animals

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Ewe wastage is the combination of on-farm mortality and premature culling. Internationally, there is limited research on actual wastage incidence and causes in commercial sheep flocks. To the authors’ knowledge, this is the first study that reports both lifetime wastage and detailed annual wastage in a sample of commercial New Zealand flocks. This study utilized data collected from 13,142 ewes from four cohorts on three commercial New Zealand farms (Farm A 2010-born, Farm A 2011-born, Farm B, Farm C), during the period 2011–2017, as they aged from replacement hoggets to 6-year-old ewes (Farm A and Farm B) or 3-year-old ewes (Farm C). Data collection visits occurred at three or four key management times each year, namely pre-mating, pregnancy diagnosis, pre-lambing and weaning. At each visit, body condition score (BCS) was assessed and any ewes that were culled or had died on farm were recorded. As this was a lifetime study, each ewe was assigned an outcome and corresponding ‘exit age’. By the end of the study, all ewes that had exited their respective flocks, were classified as either prematurely culled, or dead/missing, or if still in the flock, as censored, and either the exact date or interval in which they exited the flock was recorded. Semi-parametric competing risk (premature culling vs. dead/missing), interval-censored survival models were developed to: 1. describe the association between hogget reproductive outcomes and risk of subsequent wastage, and 2. assess pre-mating BCS as a predictor of wastage in that production year. Of the 13,142 enrolled ewes, 50.4% exited their respective flocks due to premature culling and 40.0% due to on-farm dead/missing, giving a total of 90.4% that exited due to wastage. Annual mortality incidence ranged from 3.5 to 40.2%. As a hogget, wastage incidence ranged from 7.6 to 45.4%. Pregnancy or rearing a lamb as a hogget did not increase risk of subsequent wastage. In all years, pre-mating BCS was a predictor of ewe wastage, with odds of wastage lower with increasing BCS. Therefore, farmers should focus on improving pre-mating BCS to 3.5/5.0 by assessing ewe BCS at weaning, allowing poorer-BCS ewes to be managed to gain BCS before re-breeding.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS

Flay

Ridler

Compton

et al. 2021

Animals

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“…Three studies across a range of Australian sheep production zones and systems have determined annual ewe mortality rates to range from 2.2% to 6% per annum in well managed, relatively disease‐free flocks 3–5 . Mortality rates, however, averaged 6% per annum in merino flocks affected by flystrike, 3 10% in merino ewes affected by haemonchosis 6 and 11% in crossbred flocks due to peri‐parturient problems and heliotrope poisoning 3–5 . Overseas, a large New Zealand survey of Romney Marsh ewes found that mortality rates averaged 2.8% per annum, 7 whereas a smaller survey of hill farms in the United Kingdom found that ewe mortality rates averaged between 3% and 4% per annum 8 …”

mentioning

confidence: 99%

A survey of ewe mortality on the Central Tablelands of New South Wales in 2010, a year of above‐average rainfall

Watt

Eppleston

Dhand³

2021

Aust Veterinary J

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Background Sheep producers reported elevated ewe mortality following a wetter‐than‐average season on the tablelands of New South Wales in 2010. We conducted a survey of local producers to determine the extent and cause of ewe losses, as well as associated risk factors. Methods A questionnaire was designed and posted to sheep producers running at least 1000 sheep. Data from questionnaires were analysed using linear mixed models to identify risk factors associated with ewe mortality. Data on the likely causes of deaths, particularly those associated with foot abscess, were analysed by ordinal generalised linear mixed models to determine the most prevalent causes of ewe death. Results The mean annual ewe mortality was 5.4% (range 0.1%–28.6%). Higher mortality was associated with older ewes and lambing in paddocks with longer pastures. The two most important causes of ewe death reported by farmers were ‘died during lambing’ and ‘foot abscess’. Mortality due to foot abscess was more commonly reported in adult ewes than maiden ewes (odds ratio and 95% confidence interval: 5.61; 3.52, 8.94), when lambing on pasture longer than 5 cm than ≤5 cm (2.96; 1.54, 5.70) and when lambing in spring than in autumn (4.87; 1.36, 17.41). Conclusions The level of ewe mortality observed was at the upper end of that reported previously in Australia. Risk factor analysis suggested that, in wet years, losses due to foot abscess could be reduced by lambing older heavier ewes in autumn on pasture swards less than 5 cm high.

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Balancing consumer and societal requirements for sheep meat production: An Australasian perspective

et al. 2014

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Risk factors for Merino ewe mortality on the Northern Tablelands of New South Wales, Australia

Cited by 11 publications

References 10 publications

Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS

Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS

A survey of ewe mortality on the Central Tablelands of New South Wales in 2010, a year of above‐average rainfall

Balancing consumer and societal requirements for sheep meat production: An Australasian perspective

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