Reproduction rate ... is profoundly affected by heat stress
Reproduction levels can be severely impacted by the effects of summer heat stress. The following calculator can be used to assess the impact on a farm's bottom line. The calculations behind this portion of the calculator come from research done by the University of Missouri. There is a link at the end of this article where you can upload your numbers and receive a copy of calculations for your farm.
One of the most obvious effects of summer heat stress is reduced conception rates. Most farms expect and sometimes plan for low summer conception. Poor conception means more days open and fewer productive days.
“The additional cost of heat stress hits the bottom line when it comes to fertility. As the cow’s core body temperature increases by as little as 0.5 degrees, cellular function is compromised, and the chance of an aborted embryo increases by 13 percent.”
Farms may expect poor pregnancy check results through September and even October, but the real impact on reproduction is felt the following spring. Cows that should be coming fresh in March or April are now freshening in June and July.
Not only do those cows miss out on the ideal milk-producing temperatures, but they are also calving during the higher heat stress period and struggling to reach peak production during the warmest part of the year. The impact of heat stress on reproductive performance can quickly become a vicious cycle.
What do the experts say...
Paul Fricke, Ph.D., Dairy Cattle Reproductive Specialist, UW-Madison/UW-Extension had this to say when asked “How does heat stress affect reproduction in dairy cattle both in the short and long run?” in a recent podcast interview.
Yeah, that’s a really good question. I’ll just start with the concept that high producing dairy cows produce a lot of internal heat simply as a byproduct of the increased metabolism associated with this very high level of milk production.
What we want to have happen is that cow has to be able to dissipate that heat. She has to be able to lose that heat to her environment. At lower environmental temperatures, she’s able to do that. She’s able to basically control her body temperature by losing this excess heat from metabolism and just normal functions of the body to the environment.
What happens then is when the environmental temperatures increase, that cow starts to lose the ability to dissipate that heat. There’s just a few ways she can do that.
She can basically increase her respiration so you see cows that are heat stressed that are panting. Evaporative cooling is another thing that she can do, but these cows will experience this heat stress phenomenon.
What actually happens is the normal body temperature of the cow is about 101.5 degrees Fahrenheit. You’ll see that body temperature actually increases. That’s really what the underlying physiology and the problems that happen due to heat stress is due to this increased body temperature of the cow.
In times of heat stress and severe heat stress, sometimes body temperatures in these cows can get to 105 or 106 degrees Fahrenheit.
As body temperature increases, we start to see all kinds of problems with the physiology of reproduction. Two of the major problems that we see with reproduction, one of them just has to do with estrus expression.
Every 21 days or so a non-pregnant cow will show behavioral estrus and she’ll come in and she’ll stand to be mounted by herd mates. That’s typically what we use as an indicator of when to breed that cow. One of the problems with reproduction is under periods of heat stress, the estrus expression, the duration, and intensity of estrus expression is dramatically decreased. It becomes harder and harder to see cows in estrus, so that we can actually inseminate those cows. That has a negative effect on reproduction.
The other problem with heat stress is simply on the actual fertility of the dairy cow. What happens is early during embryonic development—basically, the last few days right before a cow ovulates and the first couple days after ovulation—the early embryo is highly susceptible to these increased body temperatures that the heat stressed female is going to impose on it. That’s simply because the genome of that embryo is not been turned on. There’s a class of proteins called heat-shock proteins that can actually prevent the problem but because in this early stage of development, those proteins aren’t able to be synthesized.
This early embryo is highly susceptible to elevated maternal body temperature. What we actually see is a decrease in conception rate, which is associated essentially with the increased pregnancy loss.
The other main factor that happens with heat stress is—and we have some pretty good data from different experiments that have shown this—fertilization rates drops quite a bit as well. If you just look at the proportion of oocytes that are fertilized after an insemination, the fertilization rate will dramatically drop due to heat stress.
There are some pretty severe things that can happen on the female side that really impact reproduction and decrease reproduction performance in these lactating dairy cows.
What can CowKuhlerZ do for you?
CowKühlerZ offers a solution to heat stress that will have an impact on summer conception rates. Research has proven that evaporative cooling is the most effective method of lowering a cow’s core body temperature.
A high-velocity fan with a very focused airstream combines a timed, fine mist that acts like "imitation sweat" evaporating off the coat and causing a chilling effect that maintains core body temperature with the optimal range. The system is controlled by an intuitive controller that continuously monitors the conditions in your barn. Offering you peace of mind that your cows are being kept comfortable and cool at all times. Holding Area Systems are comprised of all the same components but offer cooling in the most stressful area of your barn without a worry, adjusting to the conditions seamlessly.
Our customers have had some phenomenal results since installing their CowKühlerZ systems. We often hear feedback like summer reproduction levels are at an all-time high. This is what one customer had to say...
"Our summer reproduction levels were fantastic in 2019 our first summer with CowKuhlerZ. The cows and heifers that freshened between May - September got back into calf on their first heat cycle. They are due to start calving in Feb, March and April, which will have a huge impact on our production levels for those months. After a summer with the CowKühlerZ system in our barn, we also know that we can maintain that production level throughout the summer months. Drops in production and missed heat cycles due to heat stress can be avoided." Farm near Woodstock ON
Preventing the impacts of heat stress can have a major impact on reproduction. Additional benefits can be found in both production and the health and well being of your herd, please check them out on the website. These numbers do not take into account energy savings or water-saving over and above other systems on the market.
Taking a few minutes to calculate heat stress losses and their impact on your dairy’s bottom line can help you strategize for better heat stress prevention, which could mean more milk, improved fertility and healthier cows and calves.
If you would like to run your numbers through the cost calculator please follow the link below and fill in the form, we will send you a PDF version of your calculator.
Cost calculator Link
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