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the mean mortality estimate and 95 confidence intervals were meaningfully different in appearance when these voyages were either included or removed. A decision was made to
remove these four voyages from the dataset for all subsequent modelling conducted in this section. The reason for this was because these voyages were extreme events and were not
considered likely to represent long term trends or overall population patterns which were important objectives for this section.
Once these four voyages were removed the dataset used for analyses included 6,443 voyages.
9.1 Mortality rate
Summary statistics were generated from 6,443 voyages over the period 1995-2012 excluding the four extreme voyages identified in exploratory screening. See Figure 11 for a
graph showing mortality rate by year.
The overall average percentage mortality deaths as a percentage of total cattle loaded was 0.15 and when expressed as a rate, 0.13 deaths per 1,000 cattle-days at sea across the
period 1995-2012.
When the time period was restricted to 2010-2012, the average percentage mortality was 0.1 and the mortality rate overall was 0.08 deaths per 1,000 cattle-days at sea.
As reported in Section 7 of this report, the average voyage mortality rate for the twenty voyages enrolled in the detailed mortality study component of this study was 0.138 deaths
per 1,000 cattle-days 95 confidence interval from 0.128 –0.148.
A recent survey of Australian feedlots described mortality rates in Australian feedlot cattle based on electronic data records from several feedlots in eastern Australia over a 12 month
period 2010-2011.
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The dataset compiled for that study comprised more than 2,000 deaths and over 25 million cattle-days at risk and the study provides a representative
estimate of mortality risk in land based feedlots. Mortality data from that study was compiled for those animals being held in feedlots for shorter periods up to 120 days, representing the
bulk of the mainstream domestic feedlot trade. The mortality rate deaths per 1,000 cattle- days at risk for feedlot cattle for all causes of death combined was 0.1 deaths per 1,000
cattle-days and for deaths due to respiratory disease was 0.06 deaths per 1,000 cattle-days at risk.
The findings from this study suggest that contemporaneous comparison of mortality rates in land based feedlots and export voyages have produced very similar estimates of mortality
rate expressed as deaths per 1,000 days.
9.2 Voyage duration
Figure 10 shows a box and whisker plot summary of voyage duration for the different regions. Voyage duration includes all days until the last cattle were unloaded at the final
destination port. In some cases, where voyages unloaded at multiple destination ports, the discharge days days from first destination port to final destination port were longer in
duration than the voyage days days from Australian load port to first destination port.
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Perkins 2013
Page 116 of 201 Figure 10: Box and whisker plot showing summary statistics for voyage duration in days
including sea voyage and discharge periods, based on data from voyages between 1995- 2012.
The central shaded box spans the range from the 25
th
percentile to the 75
th
percentile and the horizontal line within the central shaded box is the median duration. The outer whiskers
lines above and below the box, span out to a limit that is 1.5IQR where the IQR is the inter-quartile range the range from the 25
th
percentile to the 75
th
percentile. Any points that lie outside this range are plotted as shaded circles.
The box plots provide an excellent visual summary of voyage duration. The longest voyages based on median voyage duration were to SE Europe and the shortest voyages to SE Asia.
There was a wide range of voyage durations within the MENA category including individual voyages with the longest voyage duration voyage from Karumba on the QLD coast to
Egypt.
9.3 Effect of year
