1. Negative relationship between dry matter intake and the temperature-humidity index with increasing heat stress in cattle: a global meta-analysis
- Author
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Matthew T. Harrison, Andrew P. Smith, J Chang-Fung-Martel, Holger Meinke, Jaclyn N. Brown, and Richard Rawnsley
- Subjects
Hyperthermia ,Atmospheric Science ,Hot Temperature ,Passive cooling ,Health, Toxicology and Mutagenesis ,Biology ,Dairy ,03 medical and health sciences ,Animal science ,Milk production ,Pregnancy ,medicine ,Animals ,Lactation ,Dry matter ,Adaptation ,030304 developmental biology ,Original Paper ,0303 health sciences ,Heat index ,Ecology ,business.industry ,Temperature ,0402 animal and dairy science ,Humidity ,04 agricultural and veterinary sciences ,medicine.disease ,040201 dairy & animal science ,Impact ,Milk ,Negative relationship ,Active cooling ,Cattle ,Female ,Livestock ,Shading ,business ,Heat-Shock Response - Abstract
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.
- Published
- 2021