Changes in frequency and severity of heat waves due to climate change pose a considerable challenge to livestock production systems. Although it is well known that heat stress reduces feed intake in cattle, effects of heat stress vary between animal genotypes and climatic conditions and are context specific. To derive a generic global prediction that accounts for the effects of heat stress across genotypes, management and environments, we conducted a systematic literature review and a meta-analysis to assess the relationship between dry matter intake (DMI) and the temperature-humidity index (THI), two reliable variables for the measurement of feed intake and heat stress in cattle, respectively. We analysed this relationship accounting for covariation in countries, breeds, lactation stage and parity, as well as the efficacy of various physical cooling interventions. Our findings show a significant negative correlation (r =  - 0.82) between THI and DMI, with DMI reduced by 0.45 kg/day for every unit increase in THI. Although differences in the DMI-THI relationship between lactating and non-lactating cows were not significant, effects of THI on DMI varied between lactation stages. Physical cooling interventions (e.g. provision of animal shade or shelter) significantly alleviated heat stress and became increasingly important after THI 68, suggesting that this THI value could be viewed as a threshold for which cooling should be provided. Passive cooling (shading) was more effective at alleviating heat stress compared with active cooling interventions (sprinklers). Our results provide a high-level global equation for THI-DMI across studies, allowing next-users to predict effects of heat stress across environments and animal genotypes.

Item Type:	Refereed Article
Keywords:	dairy, adaptation, impact, hyperthermia, temperature, milk production
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Animal production
Research Field:	Animal growth and development
Objective Division:	Animal Production and Animal Primary Products
Objective Group:	Other animal production and animal primary products
Objective Field:	Animal adaptation to climate change
UTAS Author:	Chang-Fung-Martel, J (Ms Janine Chang Fung Martel)
UTAS Author:	Harrison, MT (Associate Professor Matthew Harrison)
UTAS Author:	Brown, JN (Dr Jaclyn Brown)
UTAS Author:	Rawnsley, R (Dr Richard Rawnsley)
UTAS Author:	Meinke, H (Professor Holger Meinke)
ID Code:	145483
Year Published:	2021
Web of Science® Times Cited:	11
Deposited By:	TIA - Research Institute
Deposited On:	2021-07-22
Last Modified:	2021-11-18
Downloads:	0