Abstract
Considering the significant influence of high ambient temperature and heat waves on the well-being and productivity of dairy cows, it is to be expected that, in the course of the next few decades, climate conditions for raising cattle will deteriorate. Research has shown that heat stress causes many negative consequences in terms of physiological and behavioural disturbances and significant losses in milk production. The effort to reduce the risk of the occurrence of heat stress among dairy cows also involves the search for new environmental methods of predicting heat stress. The aim of this paper is to review and systematise the current state of knowledge on the topic of the most widely used environmental methods of determining and predicting heat stress in dairy cows and also to show the directions of studies for the future. Based on an analysis of the most popular indexes, the study evaluated their suitability for forecasting heat stress related to maintenance systems and climate conditions for cows. However, the negative results of heat stress often appear with a delay, and a carry-over effect may be experienced (summer heat stress may affect the cows until autumn). The time of the year and breed of cows could have a big impact on when animals become sensitive to increasing heat loads. This likely can be a big contributor to the discrepancies within the different heat stress equations. It is essential to prevent the occurrence of heat stress, predicting it by observing local microclimate conditions and using meteorological forecasts. Thanks to these measures, a breeder may prepare and implement suitable solutions for protecting the animals.
Highlights
Reports published by international and government research centres indicate an increasing trend towards the systematic warming of the Earth’s climate
One index widely used both with cows kept in barns and with cows kept in pastures is THI. This index takes into account the effect of air temperature and humidity, and it is used as a general indicator of heat stress among humans (Thom 1959), in addition to its role in assessing the comfort of dairy cows as well as of other animals, especially livestock
Forecasting of heat stress risk makes it possible to limit its negative impact on cow welfare
Summary
Reports published by international and government research centres indicate an increasing trend towards the systematic warming of the Earth’s climate. Physiological and behavioural disturbances are only mechanisms of adaptation of animals to a threat to the animals’ homeostasis (Adamczyk et al 2015) They are mechanisms to cope with reduced welfare conditions, and they are strictly related to the animals’ wellbeing, so they cannot be considered as a problem themselves, but as stress indicators. Other factors influencing the risk of the occurrence of heat stress in cows include the breed of the cow, its age and lactation phase, milk production level, feed and water intake levels, the composition of feed, body condition score and the use of technical solutions to control the animal’s microclimate (Kadzere et al 2002; West 2003). The aim of this paper is to review and systematise the current state of knowledge on the topic of the most widely used environmental methods of determining and predicting heat stress in dairy cows, and to show the directions of studies for the future
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