meta Embryo Transfer FIGHTS SUMMER INFERTILITY SYNDROME! :: The Bullvine - The Dairy Information You Want To Know When You Need It


Running a dairy operation sometimes seems like a roller coaster ride. Holding on through economic and marketing challenges propels managers through numerous ups and downs.  Pregnancy rates – a key success metre in dairying — is actually one of the scariest rides of all in the dairy theme park but isn’t always recognized as such.  Because even the best pregnancy rates are not very high, too many dairy managers have become conditioned to accept the summer decline as a fact of dairy life that they can simply “ride out”. To counteract lowered pregnancy rates, you must look to embryo transfer.

Where is Your Dairy on The Pregnancy Slide?

Whenever temperatures rise above 70F, heat stress in cattle means there are fewer pregnancies per service, and this has a dramatic impact on dairy sustainability. Here in August 2015, the hot, dry temperatures are beginning to moderate but most of North America still hovers in the 80s where the effects of summer heat continue to affect embryo development and thus pregnancy rate for at least another couple of months.  Unfortunately, if you don’t take action until you hit bottom, rather than being a thrill, it might mean that your dairy profitability ride could come to an abrupt end!

What Causes the Slide?

Dairy cows originate from temperate climates and so it hot climates or during hotter parts of the year when under the stress of production the most limiting factor suffers. More recent research has shown that when temperature goes above 68F reproduction suffers

Dairy cows use energy.  The order of energy consumption is: 1. producing milk (for their young), 2. Building their body mass and then 3. Reproduction. With the addition of heat stress, the first thing to suffer is the last item in the order …. reproduction.

Under summer attack. What Happens Inside the Cow?

Reproduction research has shown:

  • eggs are not properly formed
  • internal temperature is elevated and eggs / sperm do not survive
  • fertilized eggs do not adhere to uterine wall
  • There is a domino effect as each compromise in the process negatively affects the next step.

Ovum production occurs 40-50 days before they are ovulated so only when a cow’s embryo production returns to normal can we expect to again get more reasonable reproduction rates. Areas that have mean daily temperatures above 68F for May until October can expect reproduction to suffer from late June to mid-November. That’s big time –it’s 42% of the year. For lower temperature areas off-time will be shorter but July thru Sept is still a quarter of the year.

Start with Traditional Heat Stress Tools

  • Lower temperatures by having smaller group sizes
  • Improve insect control (so animals do not group)
  • Use fans and misting
  • Make use of shade covers
  • high quality feed (more balanced diet) to breeding group
  • feed animals at night so they can rest during the heat of the day
  • breed more heifers during summer
  • use every strategy that makes sense to you and your operation

Perhaps you Need to Consider Breed and Other Alternatives?

There are breed differences with Jerseys being best at withstanding hot weather.

There is some evidence that whiter Holsteins suffer less that blacker ones

The University of Florida (and other) research shows that using embryos can produce double the number of pregnancies.


Currently, a critical mass of research is available supporting ET to combat summer infertility syndrome. Results clearly support that embryos collected from thermoneutral donors are successfully maintaining higher pregnancies rates than those achieved by heat stressed animals bred by conventional A.I. In vitro produced embryos transferred into heat stressed animals resulted in improved pregnancy rates when compared with AI during bouts of heat stress.

Of course, the expense of ET cannot be ignored. Traditionally superovulation can be quite expensive. In-vitro embryo production is gaining feasibility as an alternative.

In-vitro Production (IVP) Can Counteract Heat Losses

The laboratory production of embryos is a workable, economical alternative to traditional AI.  The primary method involves harvesting of eggs from slaughterhouse ovaries that are then fertilized with semen and grown in a laboratory for seven days. Using this method, several hundred eggs can be harvested and fertilized with one straw of genetically superior sexed or conventional semen.  The result is the production of dozens of good quality embryos. The great news is that using fresh embryos produced in vitro during the summer results in an increase in the number of heifer calves born and pregnancy rates return to levels achieved during the cooler months of the year.

How do you Measure Heat Stress?

We all know that, before you can fix anything, you must be able to measure the problem.  When considering heat stress, researchers have developed the Temperature Humidity Index.  This measures ambient temperature and relative humidity readings.  This index was developed over 50 years ago.  Original benchmarks showed that dairy cattle become heat stressed at a THI of 72. This has been revised by research produced at the University of Arizona.  Modern THI has been set to 68 as the level at which cattle become heat stressed. This considerably expands the heat stress calendar and emphasizes the need to have strategies in place to deal with the decline in reproduction.

Will you lose Money or spend it?

Embryos of high genetic merit can often be obtained for $300.

Before you look at that as a too-costly of expense consider the red hot costs of heat losses

  • $ the cost of carrying extra animals to cover lower production  (net of $3-$5 per extra animal per day)
  • $$ cost of a lost heat cycle
  • $$$ extra labor for heat detection and breeding more animals, ($25 per missed conception)
  • $$$$ semen costs ($40 per dose)
  • $$$$$ drug cost ($20-$20 per usage)
  • $$$$$$ more time spent in dry pens ($4 per day)
  • $$$$$$$ having to raise more heifers   ($2.50 per day)

The amounts you incur for the above items may be somewhat higher or lower than those we have used. The important point is that you know what it’s costing you.  Summer pregnancy losses are not free.

What are you Waiting For?

It’s one thing to recognize the issues.  It’s another to take action. Three main reasons are given for staying on the merry-go-round:

  • Unfamiliar with buying embryos
  • Setting a dollar limit. Lots of $200 to $300 would serve most breeders quite well.
  • Avoiding the accounting that shows how much is lost (see above). $175 cost of a lost heat cycle

As stated earlier results clearly support the effectiveness of embryo transfer.  University of Florida researchers published a study (2011) that concluded that vitrified embryos (42.1 %) doubled the pregnancy rate of A.I (18.3%). Furthermore, the study showed higher pregnancy rates when vitrified embryos (29.3) were compared to A.I. (18.3).

Work it Out with A Pencil

It is as if breeders think that the cool weather rates are 100%, and therefore slippage is still okay.  This is so wrong.  Average standard pregnancy rates are only 20%, and, therefore, hot weather losses reduce this to 10%.  Furthermore, the heat stressed period is not just a small percentage of the year.  Even in the northern ranges, hot weather can affect four months. In some southern areas, such as Florida, that rises to 7 months of high-temperature effects.  No matter how you do the math, this is a major loss to dairy profitability.


  • Maintain pregnancy rate of 20% throughout the summer
  • Take appropriate measures to reduce heat stress effects on milk production
  • Consider embryo transfer to maintain pregnancy rates

The Bullvine Bottom Line

When the heat is on, pregnancy rates spiral downward. Cooling strategies are proven to help milk production.  To counteract lowered pregnancy rates, you must look to embryo transfer. It’s all about money. Money wasted riding down the summer slide.  OR?  Money invested to fly higher through summer pregnancies.  The choice is yours.



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