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.