Revealing and exploiting the diversity in dairy cattle reticulorumen temperature data for heat stress amelioration

Abstract

Dairy farming in Australia occurs across diverse environments, increasingly affected by climate variability and the resulting risk of heat stress. Cattle response to heat stress takes on a variety of forms, aiming to return the animal to thermal stability. Driven by the potential to improve cattle welfare under challenging climatic conditions, this thesis aims to reveal and exploit the diversity in dairy cattle reticulorumen temperature data for heat stress amelioration. The literature review explores animal responses to heat stress, methods of monitoring, and heat amelioration techniques, revealing the benefits of a data-driven amelioration approach. A review of heat abatement terminology establishes clear definitions for key terms. Development of a drinking event detection model provides algorithm transparency in the isolation of drinking behaviour using reticulorumen boluses. Exploration of temporal variability in drinking behaviour of dairy cattle confirms seasonal variation in drinking frequency, reticulorumen temperature change, and drinking-recovery duration, improving our understanding of core body temperature diversity. Time series and mixed model analysis are used to link the reticulorumen temperature response of dairy cattle to variations in temperature humidity index. Results indicate significant variability in sensitivity to thermal change among individuals alongside the importance of baseline temperature humidity index levels. The association between three phenotypic indicators for heat tolerance are then assessed. All traits reveal significant individual animal diversity in response to thermal deviations. Analysis of slopes confirms important inter-trait relationships for heat stress response, highlighting the potential for drinking frequency to be monitored on farm as a proxy for heat stress. This work contributes to enhanced welfare and productivity across the dairy industry, supporting progress towards a climate-smart, sustainable future.