28/02/2025
Stocking density may impact sheep welfare during live export voyages that occur under hot and humid conditions.
This has been the focus of a recent study conducted as part of a Project Partnership between the Livestock Export RD&E Program and the University of New England.
The study evaluated some key welfare indicators in sheep housed at three different stocking densities (space allowance per animal) under conditions simulating those encountered during livestock export voyages from Australia to the Middle East. The sheep underwent an 8-day adaptation period to replicate the conditions of Fremantle port, followed by a 21-day exposure period to mimic the climate and stocking densities typically experienced on a voyage. Throughout the study, rumen temperatures, biological function indicators, behaviour assessments, and respiration rates were recorded and evaluated.
The results of this study have now been published in the Journal of Animal Science.
The study found that the hot conditions assessed had no important impact on biological functioning under regulated stocking densities, suggesting that on average, the sheep were able to tolerate the land-based, experimental climatic conditions tested in the study, based on the specific indicators of welfare and heat stress assessed in the study.
Stocking density had no important effect on the number of sheep lying down when assessed at multiple timepoints throughout each day, but did affect some lying positions. In the lower stocking density pens, more sheep were lying with outstretched legs and in physical isolation from other sheep in the pen, which may have helped to enhance heat loss and improve thermal comfort. However, at all stocking densities assessed, it appears the sheep had an equal ability to thermoregulate, as on average, stocking density did not substantially impact core temperature (as indicated by rumen temperature).
On average, the intensity of the hot and humid conditions assessed wasn't high enough to trigger important changes in the sheep’s stress hormones or affect their overall biological functions. The sheep in pens with lower stocking densities showed slightly lower respiration rates compared to those in higher stocking densities when exposed to high wet bulb temperatures. Despite this, increased respiration rates remained an effective method for heat dissipation for most sheep.
As the wet bulb temperature increased, the number of aggressive interactions decreased across all stocking densities, suggesting that the sheep reduced their activity to minimise heat production.