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In summary, the logistic regression model is of limited use because of the small number of case voyages. Caution should be applied to avoid over interpretation of the findings.
Nontheless, the most substantive finding of this analysis is that there appears to be an increased risk of mortality events for voyages containing sheep that were loaded at Portland. This finding is
consistent with the findings from the negative binomial modelling discussed in the previous section.
While some caution is advised, the findings also suggest that there is little difference between sheep loaded in Adelaide and sheep loaded in Fremantle with respect to the risk of a reportable mortality
event.
6.3 Results of statistical analyses in context
The findings described above from the last six years of voyages, are consistent with earlier reports Norris and Norman, 2003, Norris and Norman, 2010.
The major findings from the analyses described above are: Within any one year there can be variability in mortality rates.
An overall pattern displayed by the overall average line which suggests a low mortality rate in the first four months of the year, followed by a gradual rise to a peak in August and then a gradual
decline between August and December. Overall monthly voyage mortalities remain above 1 until after October.
Within this pattern, there appears to be a distinct difference between voyages containing sheep loaded at Portland and voyages containing sheep loaded at Fremantle. Voyages containing
sheep loaded at Portland have a more dramatic rise in mortality rate which peaks in July and remains high in August before falling to merge with the overall pattern by September.
There is insufficient data to make conclusions about patterns for voyages containing sheep from Adelaide. These voyages do show a rise in the latter part of the year but within that there is
variability due to individual voyages that may occur at any time. The results of the logistic regression analysis support a conclusion of elevated risk of a
reportable mortality event for voyages in the winter months that included sheep loaded at Portland, and that there was little evidence of any difference between voyages containing sheep
loaded in Adelaide and those containing only sheep loaded in Fremantle.
There is year to year variation which resulted in the highest overall annual mortality rate in 2009 and the lowest overall annual mortality rate in 2011.
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There is no evidence to suggest that the rise in mortality rates in the mid to latter months of the year may be associated with an increase in total sheep numbers loaded per voyage. ASEL
restrictions concerning sheep from southern ports to the Middle East There are a number of areas where the current ASEL stipulates specific requirements relating to
export of sheep from southern ports to the Middle East. Most of these specific requirements are found in Standard 3, relating to management of livestock in
the registered premises. The only specific requirement relating to export of sheep from southern ports in winter that appears
elsewhere in the ASEL is the section 4.1.6 relating to minimum pen area per head for sheep and goats that has different requirements for the periods from November to April, and May to October.
Within Standard 3, there are two broad areas where the ASEL content may be viewed as providing guidance for management of livestock during winter months.
The first relates to non-specific requirements such as Standards 3.4 and 3.5 that relate to issues such as drainage and shelter from climatic extremes. These requirements may be considered to be
important in winter months when there may be rain, wind and cold weather that can result in adverse effects on animal welfare due to the direct effects of thermal stress or indirect effects associated with
adverse impacts of stress on immune function and potential increased risk of pathogen exposure. The requirements in the ASEL relating to drainage and shelter are considered appropriate.
The second area where the ASEL is relevant to preparation of sheep in winter months relates to specific requirements:
S3.7 c iii: use of fully sheltered feed troughs S3.8 a: sheep in paddocks to be held for 5 clear days at the premises in winter with ad lib
feeding with onboard pellets for 3 clear days S3.9 a: restrictions on the type of sheep that can be prepared for export to the Middle East
between May-October. S3.9 b: All sheep being prepared for export to the Middle East between May-October must
have wool not more than 25 mm in length and must be at least 10 days off shears on arrival at the premises.
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6.4 Origins of ASEL requirements
