What producers need to be aware of
The summer’s heat stress can impact the cows and bulls through changes in the duration and intensity of estrus, follicular development, and can also compromise embryonic development. “Heat stress in cattle occurs when heat gain becomes greater than an animal’s ability to lose heat,” said Dan Stein, assistant professor in livestock production in the animal science department at Oklahoma State University. “During the high temperature days this summer, cattle accumulated internal heat, which must be released during the night time. When even the night time temperatures were high, especially for extended periods of time, effective heat removal was not possible.”
Stein tells producers that the breeding season will possibly be shortened due to the onset of the heat stress period.
The cows
“The greater effect may be on cow and heifer body condition scores,” said Dr. Craig Payne, extension veterinarian for the University of Missouri. “Chronic heat stress not only impacts intakes but forage quantity and quality rapidly declines later in the summer and excessive heat exacerbates this problem. Producers are encouraged to monitor body condition scores and feed accordingly to avoid breed back problems later on.”
“If cows are in a moderately thin body condition when they calve, and if we don’t have good fall forage production, we will find more open cows at the end of the breeding season,” said Shane Gadberry, associate professor at the University of Arkansas.
“Feedstuffs are very expensive right now,” Gadberry said. “With current estimates of corn yields expected lower than projected, the heavy demand for corn and short hay supplies, feeding the herd this winter will be very expensive. Pregnancy-checking and marketing open cows will help reduce grazing pressure and help pastures recover this fall and reduce hay and supplement needs this winter.”
The bulls
Another effect to keep in mind is the productivity of the bulls. “There are several studies demonstrating that periods of excessive heat can have a negative impact on sperm motility and development thereby leading to a temporary decrease in bull fertility,” Payne said. “Operations that had breeding seasons lasting through July and August could experience poorer conception rates because of this effect.”
Stein added that depending on when the heat stress ended producers need to remember sperm production takes about 63 days from start to finish. Also, producers need to realize that even though a bull passed a breeding soundness exam this year, there is no guarantee the bull will pass one this upcoming breeding season.
“Regardless of what season cows are calving in, producers should have a breeding soundness exam performed on their bulls prior to the upcoming breeding season,” Stein said.
What to do now
This year, producers are being advised to conduct early pregnancy examinations more so than “normal” years. “This year there are factors in existence that may increase the percentage of open cows,” Payne added. “Early examination gives the producer a degree of flexibility with marketing culls that they may not have otherwise.”
Another opportunity producers may have, is to re-breed open cows and sell them as bred cows potentially capturing greater value. “In addition to marketing flexibility, early pregnancy examination and culling also preserves valuable feed resources which may be in short supply during extremely hot summers,” Payne added.
If producers have concerns about their cattle’s reproduction capabilities and related health and economic issues, Payne encourages producers to seek advice from a qualified farm financial advisor from the private sector or visit with an agriculture business specialist at their local extension office. “The one-on-one interaction they will receive will be invaluable when trying to determine the optimal strategy for dealing with their particular situation,” Payne concluded.


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