New strategies to mitigate heat stress in high-producing dairy cows

The impact of climate change on dairy production highlights the urgent need to adopt integrated and sustainable strategies. – Article published in the June issue Albéitar.

Irina Garcia-Ispierto
Professor Professor. Department of Animal Science, University of Lleida. Agrotechnic

The impact of climate change on dairy production, especially through the prism of heat stress affecting cows, highlights the urgent need to adopt integrated and sustainable strategies to mitigate its adverse effects. The review addresses this problem from multiple fronts, including the implementation of adequate infrastructure and cooling systems, the optimization of animal nutrition to improve heat resistance and strengthening the immune system, as well as genetic selection and genomic editing to develop more resilient breeds. These measures, framed within the concept of “One Welfare”, not only seek to preserve animal productivity and well-being in the face of climate challenges, but also reduce the environmental impact of the dairy industry, pointing towards greater sustainability and efficiency in the context. of a changing climate.

Keywords: climate change, dairy production, heat stress, environmental impact.

New strategies to mitigate heat stress in high production dairy cows

The impact of climate change on dairy production, particularly through the lens of thermal stress affecting dairy cows, underscores the urgent need for integrated and sustainable strategies to mitigate its adverse effects. This review addresses the issue from multiple angles, including the implementation of appropriate infrastructure and cooling systems, optimization of animal nutrition to enhance heat resistance and strengthening immune system, as well as genetic selection and genomic editing to develop more resilient breeds. Framed within the “One Welfare” concept, these measures aim not only to preserve productivity and animal well-being in the face of climatic challenges but also to reduce the environmental impact of the dairy industry, pointing towards greater sustainability and efficiency in the context of a changing climate.

Keywords: climate change, dairy production, heat stress, environmental impact.

Introduction

In the current situation, the phenomenon of climate change is established as an inevitable reality, exerting a profound impact on humanity, fauna and the environment. Within this context, the “One Welfare” paradigm acquires unprecedented relevance, underlining the interconnection between animal, human and ecological well-being. In particular, the dairy cow, considered a key factor in the fight against world hunger, faces great challenges due to heat stress.

The primary objective of dairy herds, beyond dairy production under an economically sustainable framework, lies in achieving environmental sustainability. Although global progress in terms of management and genetic improvement of these herds has led to an increase in milk production, a significant decline in fertility has been observed since the mid-1980s (Lucy, 2001; López-Gatius , 2003). This fact is surely multifactorial and not only due to this selection. Management and environmental conditions are also presented as determining factors that influence the reproductive and productive capacity of dairy cattle.

Thermal stress (TS) is characterized as the response to external stimuli that cause an alteration of the basal state body temperature in homeothermic animals (Yousef, 1984). For dairy cows, optimal temperatures are in the range of 5 to 25 °C, constituting their thermal comfort zone (Mc Dowell, 1972). In this range, animals are able to maintain their body temperature without incurring additional energy expenditure, which favors optimal productivity at a minimum physiological cost. However, the global increase in temperatures has caused heat stress, previously seen as a problem exclusive to tropical areas, to extend to more northern latitudes, evidenced by the increase in the number of days in which the temperature index- Humidity (THI) exceeds comfort thresholds in regions such as northern Europe, the United States and Canada. This phenomenon, together with the growth in the number of animals per farm and the intensification of production, currently represents one of the main challenges for the dairy industry.

Heat stress has a negative impact on the health and biological functionality of dairy cows in the following way (Beatty, 2015; Bohmanova, 2007; Garcia-Ispierto et al., 2007):

• Affecting the production and quality of milk.
• Reducing food intake by up to 40%.
• Decreasing fertility and increasing initial embryonic/fetal loss (figure 1).
• Altering the bacterial composition and metabolism in the rumen.
• Weakening the immune response and resistance to oxidative stress.
• Deteriorating the well-being and mood of the cows, which generates hunger, thirst, frustration, aggression and pain.

Thus, ET not only drastically reduces productive efficiency on farms, but also increases the carbon footprint and methane emissions, due to the need to maintain a greater number of animals to achieve the desired levels of milk production. In this way, the climate crisis becomes more visible, underlining the need to adopt more sustainable and environmentally friendly practices in dairy production.

The objective of this review is to explore and evaluate emerging strategies to mitigate heat stress in high-producing dairy cows, with special focus on innovations in management, genetics, nutrition and applicable technology. It seeks to provide a compendium of current solutions that can be implemented to improve the well-being of dairy cows, increase their productive efficiency and reduce the environmental impact of dairy production in the context of climate change. The specific objectives of this review are:

• Explore emerging strategies. Focus on mitigating heat stress in high-producing dairy cows, addressing the challenges imposed by climate change and its effects on dairy production.
• Study innovations in management, genetics, nutrition and technology. Examine innovations in several key areas, including herd management, genetic improvements, advanced nutritional strategies and the implementation of applicable technologies, that can contribute to the adaptation and mitigation of heat stress in dairy cows.

Facilities

The implementation of adequate shelters is the best strategy for protecting animals against extreme weather conditions, guaranteeing their optimal development, health and productivity. Thermal stress can be effectively reduced by applying architectural design principles focused on the structural and thermophysical characteristics of facilities, including consideration of form, orientation, construction materials, and the implementation of efficient ventilation systems. Shading animals is a very effective way to protect them from the sun. However, to combat heat and humidity, additional strategies must be applied (Kalyan et al., 2013).

To keep cows cool and help heat move from the inside to the outside more efficiently, it is vital to use cooling methods, which can be direct or indirect. Among these techniques, evaporative cooling stands out as the most effective, especially when common methods such as radiation and conduction are not sufficient. This is achieved through cooling pads and ventilation systems that improve the environment in which the animals live (Dunshea et al., 2013). Direct cooling methods such as misting, misting, and mist generation systems work best in dry environments by cooling the surrounding air through the rapid evaporation of small water droplets (Bah et al., 2021).

On the other hand, indirect cooling approaches, using cooling pads and fans, are cost-effective and particularly useful in arid areas, as they avoid increased humidity that could result from direct wetting of animals. These techniques not only reduce heat stress, but also encourage greater dry matter intake, leading to a notable increase in milk production. A study conducted by Macavoray et al. (2023) evaluated the impact of additional spray cooling sessions during semi-arid summer nights in Pakistan, observing an average increase in milk production of 2.9 kg/day in cows subjected to eight cooling sessions compared to five sessions. Additionally, research has shown that shading combined with intermittent spraying and forced air movement is a very effective method of cooling dairy cows, thereby reducing production losses during hot and humid weather conditions.

This article appears in issue 266 (May/June 2024) of Albéitar. Subscribe here to have full access to this and other magazine content.

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