Source: AgriLife Today | March 29, 2021
Winter Storm Uri could have long-term effects on Texas’ cattle herd. Texas A&M AgriLife Extension Service specialists recently expressed concerns about bull reproductive soundness being affected by frostbite.
Some of these effects may include increased bull culling rates, delayed breeding seasons, lower conception rates, and lighter calf weaning weights, all of which have economic consequences, according to the AgriLife Extension experts.
“We are encouraging beef cattle producers to conduct breeding soundness examinations (BSE) on bulls prior to the spring breeding season,” said Jason Smith, Ph.D., AgriLife Extension beef cattle specialist, Amarillo. “While always a good practice, conducting a BSE this year is probably more important than ever in the recent past.”
Joining Smith in expressing concerns are Ron Gill, Ph.D., AgriLife Extension beef cattle specialist, and Tom Hairgrove, DVM, Ph.D., AgriLife Extension cattle veterinary specialist, both in Bryan-College Station. All three are in the Department of Animal Science within Texas A&M University’s College of Agriculture and Life Sciences.
Following the February winter storm that produced record low temperatures across a large portion of the state, there is concern among the experts about the presence of frostbite on some breeding bulls. Others have expressed concern about reduced sperm production and quality, even if no frostbite was observed on the scrotum.
Testing of bulls for the spring breeding season recently began, and there have been reports from veterinarians and AgriLife Extension agents of higher-than-normal BSE failures in bulls, Smith said.
“While it is difficult to estimate the extent to which a specific operation’s bull battery may or may not have been affected by abnormally low temperatures and extended snow and ice cover, one thing remains certain … a pre-breeding BSE is the only way to objectively evaluate a bull’s readiness to breed prior to turnout,” Smith said.
Bull testing should be a priority
Producers are encouraged to request a complete BSE that includes evaluation for motility, morphology and physical defects as well as testing for Trichomoniasis, Gill said. Most often a quick screening for sperm motility constitutes a “fertility test” on bulls. Morphology is as important to a sperm’s ability to fertilize an oocyte and is often not looked at during routine BSEs conducted in the field. The value of a complete BSE cannot be overemphasized, he said.
“We want to make best management recommendations to help producers mitigate any negative consequences of the recent winter storm on bull fertility,” Smith said.
Hairgrove, who is actively collecting data from veterinarians in collaboration with Ky Pohler, Ph.D., Department of Animal Science reproductive physiologist, will be analyzing and using that data to provide reproduction recommendations.
Early observations indicate a higher-than-normal rate of BSE failure or deferment to re-test in bulls with visual signs of frostbite, Hairgrove said. It appears that a large portion of those are likely due to physical/structural defects to spermatozoa that can be attributed to damage that occurred during storage in the epididymis.
“From a conceptual standpoint, the damage most likely occurred due to excessive testicular heating in response to the frostbite,” Smith said. “Similar consequences would be expected during times of extreme heat stress, such as is often the case throughout the summer months in Texas.
“We also preliminarily expect younger bulls to have been more resilient to the extreme cold, as they have a greater ability to raise their testes to regulate scrotal temperature and prevent frostbite. However, we do not yet have the objective data to support that notion.”
Don’t panic, but take action
The experts said it could be that many of the bulls that fail a BSE or are deferred to re-test may recover and pass a BSE without requiring a full 60-day cycle of spermatogenesis to do so.
It is also important to recognize that even in a normal year the rate of BSE failure is in the realm of 15% to 20% of bulls tested, and therefore approximately one out of every five bulls would be expected to fail a BSE, Smith said.
Hairgrove added that “while it is likely there will be a small portion of bulls that will be non-breeders due to physical damage and inability to breed cows, those bulls should be quickly identified by a BSE.
“This extreme weather event is one of many reasons why working with your veterinarian to conduct a pre-breeding BSE on all bulls is always advised, regardless of past performance,” Smith said. “This is also true for recently purchased bulls that underwent a BSE prior to the winter storm. For producers who do not routinely conduct pre-breeding BSE’s, this would certainly be the year to start, and to start early.”
The experts said the knowledge gained by testing will provide producers with the ability to decide if they need to replace bulls while replacements are still available, or if they need to turn out more bulls than normal.
“A key takeaway from this is to not panic and not immediately cull all bulls that fail a BSE or are deferred for re-test,” Gill said. “Once results are known on the initial tests, plans can be made to locate additional sires if needed, or a plan can be developed to rotate sires in and out during the breeding season.”
The experts said that, following the re-test, they expect some of the deferred bulls to pass a BSE.