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Reproductive performance of northern Australia beef herds. 7. Risk factors affecting mortality rates of pregnant cows

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Fordyce, G., McCosker, K. D., Smith, D. R., Perkins, N. R., O'Rourke, P. K. and McGowan, M. R. (2023) Reproductive performance of northern Australia beef herds. 7. Risk factors affecting mortality rates of pregnant cows. Animal Production Science, 63 (4). pp. 378-387.


Article Link: https://doi.org/10.1071/AN19431

Publisher URL: https://www.publish.csiro.au/paper/AN19431


Context: There are multiple reports of high annual cow mortality rates in northern Australia, but no reports clearly indicating the overall rates and the impact of primary risk factors.Aims: The research aimed to determine which measured region-, property-, management group- and animal-level risk factors are associated with missing pregnant females.Methods: Risk factors for the annual rate of pregnant-cow mortality were investigated in an epidemiological study using outcomes for 21 554 cows from 52 beef herds in 2009 and 2010 in four primary country types within the mostly-dry tropical north Australian environment. Modelling of 2001–2011 Australian beef-herd statistics was used to corroborate and further quantify findings.Key results: In the epidemiological study, the overall predicted annual mean incidence of missing pregnant cows, a surrogate for mortality, was 10.9%, including lost tags and unrecorded cow movement that were estimated to constitute up to 9% missing cows. Risk factors associated with higher pregnant-cow mortality were as follows: not having follow-up rainfall more than 30 days after the first wet-season storms (4 percentage point increase); <2 t/ha of available pasture biomass in the early dry season (2–6 percentage point increase); pasture dry-season biomass <2 t/ha interacting with less than moderate mid-dry-season body condition score (3–10 percentage point increase); and, calving between April and September (non-significant trend for a 1–2 percentage point increase). Feed-quality measures did not affect mortality rate. Population modelling of Australian beef herd statistics suggested an average annual cow mortality rate in the Northern Forest region of ~7% compared with 2% in more nutritionally endowed regions.Conclusions: The major risk factor for cow mortality is under-nutrition, related either to generally-low soil fertility, seasonally-dry conditions, or management that exposes animals to poor nutrition. Annual mortality of pregnant cows appears 6–9 percentage points higher in the low-fertility Northern Forest region than elsewhere.Implications: Beef cow mortality is a major business cost in northern Australia. The efficacy of targeted management to achieve high cow performance was demonstrated by losses in a third of studied businesses in the Northern Forest being kept to the same or lower levels as median loss in endowed regions.

Item Type:Article
Corporate Creators:Department of Agriculture and Fisheries, Queensland
Business groups:Animal Science
Keywords:beef cattle, mortality, northern Australia, production systems.
Subjects:Science > Biology > Reproduction
Animal culture > Breeding and breeds
Animal culture > Cattle
Live Archive:22 Jun 2023 06:16
Last Modified:22 Jun 2023 06:16

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