Refinement of the Heat Load Index Based on Animal Factors

Summary

In Australia climatic conditions will sometimes impact on the performance and welfare of feedlot cattle. High ambient temperature, relative humidity, solar load and low wind speed can result in production losses and in extreme cases death. In order to cope with environmental stressors, cattle can within limits adjust physiologically and behaviorally to cope with the stressors. Livestock managers need to recognize these responses and use them as an aid in combination with the heat load index and panting scores. Managers can then make informed decisions on when to use heat stress reduction strategies in an effort to minimise production losses. The assessment of the heat load status of cattle is difficult. Managers have tools such as the heat load index, the accumulated heat load index and panting scores to assess the impact of climate changes on their animals.

By using a combination of local climatic conditions and animal responses to the climate (e.g. panting scores and animal behaviour) feedlot management will be well placed to implement strategies to reduce the impact of severe hot weather conditions on their cattle. However, changes in livestock behavioural due to prevailing weather conditions are not well understood. In addition, behavioural of cattle with access to shade have not been fully studied.