Season, age and adiposity influence death rates in sheep exported by sea

Abstract

A study was conducted to determine the role of season, age and adiposity in the cause of sheep deaths during sea transport from Fremantle to the Middle East. Death rates were higher in the second half of the year in 4 of 5 years. Shipboard death rates in hogget wethers were approximately half those of adult wethers in each of three methods of comparison. Sheep condition (adiposity) was positively correlated with the proportion of sheep that did not eat pellets in the feedlot (P < 0.05) and with shipboard mortality (P < 0.01) in two of three voyages. Individual sheep that were identified as fat had approximately twice the risk of death from inanition aboard ship than sheep identified as not fat. Adiposity was identified as a central factor leading to a syndrome of persistent inappetance. The pathogenesis of this syndrome in adult wethers may be linked to interference with the seasonal control of appetite and energy metabolism. The lower death rate in younger wethers was attributed to the overriding demands of tissue growth, ensuring a stronger appetite than that seen in adult animals.

Cattle deaths during sea transport from Australia

“…The death rate has been defined, the causes of death established and the main risk factors identified. [1][2][3][4][5] In these studies, analysis of ship Masters' reports was a valuable method of establishing the death rate and identifying some of the risk factors. 1 The present report describes the results of investigations into the deaths of cattle during sea transport from Australia.…”

Mortality of sheep exported by sea: evidence of similarity by farm group and of regional differences

“…The study was conducted in the second half of each year only, as death rates are higher than in the first half. 4 Additional mortality data were provided from 10 research voyages conducted from 1985 to 1993 where mortalities were recorded by farm group. In the final year of monitoring (1996), the owners or managers of groups of sheep that were included in the database were contacted by telephone to increase the likelihood that their sheep would be identified upon arrival at the export feedlot and then monitored aboard ship.…”

“…For each consignment, the mortality rate was assigned its percentile ranking, within the month and year of loading, to remove any effects of season and year. 1,4 A percentile ranking is the rank, in percent, for a value in a set of data. For example, the percentile ranks for each value in the set of data 1, 2, 3, 4 and 5 are 0, 25, 50, 75 and 100 respectively.…”

“…different voyages, death rates followed a seasonal pattern and were higher in the second half of the year. 4 In addition to the seasonal pattern, the mortality of sheep from different farms varied considerably. In an epidemiological study of sheep deaths, Norris et al 5 found that half of all deaths aboard ship occurred in 25% of 133 farm groups of sheep with death rates as high as 14%.…”

Inanition, stress and immunity in the expression of salmonellosis in the live sheep export industry

“…"Shy feeding" and inappetence is relatively common in mature sheep (6). However, in young sheep up to 3 years of age a strong feeding drive is present and the true "shy feeding" rate appears to be very low, probably less than 0.5%.…”