Wetting cattle to alleviate heat stress on ships+

Summary

This report details the results of a study commissioned by LiveCorp/MLA to investigate the effects of cooling Angus steers (mean live weight = 355 kg) with water on pen microclimate, feed intake, respiration rate, panting score, body surface temperature and behaviour when exposed to dry bulb temperatures (DBT) > 30 oC and wet bulb temperatures (WBT) > 30 oC for 4 days. The steers (n=18) were housed in groups of nine (1.427 m2/hd) in an enclosed climate controlled room in a pen designed to replicate ship board conditions. Water was applied by (i) a hose, (ii) overhead sprinklers, (iii) sprinklers at leg height, or (iv) misting. Fans ensured adequate air movement. To replicate seawater conditions in the northern Indian Ocean water was heated to 30 oC and contained 3% salt. DBT, WBT, air pressure, and atmospheric ammonia concentration were recorded. Hose, overhead sprinklers and misting were successful in reducing cattle heat load. Leg wetting was ineffective because dominant cattle restricted sprinkler access. Misting used the most water (5483 L) and the hose the least (845 L). The application of water resulted in significant falls (> 3 oC) in DBT, and zero or < 1oC increases in WBT. These result, show that wetting cattle as a method of reducing the effects of high heat load can be carried out in environments where WBT is high with little negative impact on the microclimate. It is necessary to remove bedding prior to or during wetting to ensure ammonia levels remain low.