Climate change is not simply a subject of debate; it’s a present and pressing issue, especially in our agricultural sectors. With its relentless rise in temperature, hot days and heat waves are becoming common occurrences. These changes are posing increasing risks of heat stress for livestock, particularly dairy cattle. As a result, the dairy industry suffers significant economic losses due to reductions in milk production, reproductive issues, and increased treatment and disease management costs.
According to recent assessments conducted in the U.S., the dairy industry endures an average global loss of approximately US$1.2 billion per year in lactating cows due to heat stress effects. To mitigate such losses, we’ve got to first comprehend the physiological response of these animals to heat stress. Recognizing the enemy is, after all, the first step towards an effective defense.
A recent study illuminates the pros and cons of various strategies that scientists are using to select for thermotolerance in dairy cattle. These strategies include initiatives like incorporating reduced milk production, crossbreeding with Bos Indicus breeds with Bos Taurus breeds, and gene editing to imprint specific genes or mutations for resilience against heat stress. However, while these methods have their merits, they’re not one-size-fits-all solutions, especially for countries with varying seasons. For instance, crossbred offsprings, bred specifically for heat-resistance, may become more susceptible to cold stress during winter months.
In response, many scientists are studying and proposing the inclusion of physiological and cellular traits involved in cooling during heat stress as a promising solution for dairy cattle thermotolerance. This might encompass traits like a lower respiration rate and stable rectal temperature. However, implementing these traits in selection programs poses its own set of challenges. For instance, our bovine friends have shown low heritability for respiration rates, leading to slower genetic gains when selectively breeding based on this trait alone.
On a cellular level, traits such as nitric oxide synthesis are associated with thermotolerance. These traits aid in skin vasodilation during heat stress, helping in releasing excess heat to the environment.
“Aside from the physiological and cellular strategies, the selection for high immune response has emerged as an effective strategy in fostering thermotolerance. Recent studies have shown that dairy cattle identified as high immune responders are surprisingly more thermotolerant than those identified as average and low responders.”
Multiple studies have confirmed that high immigrant responding dairy cows have lower respiration rates at higher THI (Temperature-Humidity Index) values compared to average and low responders. Thanks to advancements in genetic research and technology, the selection for high immune response in dairy cattle is becoming increasingly approachable and cost-effective. Traits like these are proving to be an ideal and budget-friendly selection strategy for improving thermotolerance while maintaining production levels and minimizing cold stress. Encouragingly, these “super cows” have shown no compromises in milk production compared to their herd mates, making this strategy even more promising for the dairy industry.
In the face of climate change, new challenges arise, but so do innovative solutions. With strategic selection and breeding, we can help our dairy herds stay cool in the heat and maintain a profitable and sustainable production scale.
Understanding the Importance of Thermotolerance in Dairy Cattle
Recognizing the impact of heat stress on dairy cattle and adopting the right selection strategies for thermotolerance, is a crucial element in dairy livestock management. Dairy cows, particularly the high-producing breeds like Holstein, are dramatically affected by heat stress due to their high metabolic activity during lactation. This makes thermotolerance an essential trait for selection and breeding.
Estimating the genetic parameters for heat tolerance is a key undertaking in effective dairy cattle breeding programs. Interestingly, studies have unearthed specific genes and gene markers tied to thermotolerance in dairy breeds such as Holsteins. These novel discoveries have paved the way for remarkable progress in improving our bovine friends’ genetic resistance to heat stress.
Various initiatives, like the genomic estimated breeding values (GEBV) developed in Australia, aim to enhance heat tolerance in dairy cattle. By selecting thermotolerant animals, we can optimize dairy cattle’s performance, especially during the summer months when heat stress can result in reduced milk yield and fertility.
However, it’s essential to acknowledge the potential flipside of this coin. By selecting for thermotolerance, we might inadvertently render our dairy cattle more susceptible to cold stress, especially in regions infamous for their extreme winter temperatures. There’s also the risk of unintentionally decreasing milk yield.
Encouragement can be found in recent Australian studies by Cheruiyot et al. These are focused on upscaling heat tolerance in dairy cattle and continue to uncover genomic sites of critical importance for body temperature regulation. Their research has shown that selection for thermotolerance is practical and achievable.
While the recording of rectal temperature on dairy farms is infrequent, making direct selection based on this variable less feasible, genetic markers predicting thermotolerance have been identified using data on rectal temperature variations. These markers are invaluable tools for breeders in picking the most thermotolerant animals, thus fostering a heat-resilient future for our dairy cattle.
Proven Strategies for Improving Thermotolerance in Dairy Cattle
In recent years, breakthroughs in genetic research have pointed the way to effective strategies for enhancing thermotolerance in dairy cattle. Let’s dive into some of these strategies that could be a game-changer in the world of dairy farming.
Selection of thermotolerant animals is the first step towards better performance of dairy cattle in hotter climates. Australia, a country where heat stress amongst livestock is quite common, has been at the forefront of this research. In a series of studies conducted by influential researchers like Cheruiyot and his team in the years 2020, 2021, and 2022, Australia has worked towards bagging some impressive findings that have helped in combating heat stress amongst dairy cattle.
These studies have been pivotal in identifying certain specific genes and gene markers related to thermotolerance in dairy breeds like Holsteins. This discovery has significantly increased the probability of progress in improving genetic resistance to heat stress, a milestone towards thermotolerant dairy cattle.
Another remarkable strategy has centered around the use of genomic estimated breeding values (GEBV) for heat tolerant dairy cows. GEBVs essentially help to predict the genetic potential of an animal, thereby allowing breeders to confidently select the best animals for breeding. By identifying animals with superior GEBVs for thermotolerance, progress has been made in a direction that leads to a herd of heat-tolerant cattle.
The Bottom Line
The first step to successful thermotolerance selection in dairy cattle begins with an understanding of the importance of such a trait. With impacts ranging from productivity to health, it’s clear that thermotolerance is a valuable attribute in the dairy sector. As we explore proven strategies such as ACT, RUM, EAT, and SCS, the role of a thorough selection protocol becomes even more critical.
Research, including studies from authorities such as Binsiya, T.K. et al. (2017), suggest that attention to fertility, health, and traits like the Balanced Performance Index (BPI) can improve our thermotolerance selection processes. Yet, more research is needed to bring clarity to this subject, confirming initial hypotheses and revealing possible novel strategies for thermotolerance selection.
Ultimately, the journey towards successful thermotolerance selection is a continuous learning and adaptation process. Incorporating proven strategies with innovative methods based on latest research, we can improve the overall well-being and productivity of our dairy cattle, meeting the demands of a globally growing dairy sector.
