BRFT discusses heifer puberty and fertility prediction improvements
During the Beef Reproductive Task Force’s (BRFT) first monthly webinar of 2022, released on Jan. 18, University of Missouri (MU) Animal Sciences Research Center Associate Professor and Wurdack Chair in Animal Genetics Dr. Jared Decker discussed current genomic research and observation taking place in an effort to improve puberty and fertility predictions for beef heifers.
“I’m of the opinion genetic predictions for fertility traits in the beef industry are lacking,” Decker states at the beginning of his discussion. “Historically, fertility traits such as heifer pregnancy and stability tend to have lower accuracies in the suite of traits published by breed associations. So, predicting these fertility traits can be difficult.”
According to Decker, one of the overarching reasons the beef industry needs to see improvement in these genetic predictions is because fertility traits and reproductive outcomes are often the two largest predictors of profitability for beef operations.
“If a beef operation has a carrying cost of either developing a heifer or maintaining a cow and no calf is produced, there is a lot of investment for little to no sellable product,” he says. “Since marketing calves is what we do in the beef industry, it is so important for producers to have a live, healthy calf on the ground, and obviously, the first step in this process is fertility and production.”
Improving genetic predictions
In order to improve genetic predictions, Decker believes there needs to be more hard, quantitative data on which heifers in a breeding program are ready to be bred, not ready to be bred or have been too delayed in their development to ever be good candidates for a breeding program.
He points out a few traits can be measured during both a pre-breeding exam and pregnancy exam he believes are helpful. These include reproductive tract scores, pelvic measurements and fetal age.
Through observation of the MU Show-Me-Select Replacement Heifer Program and current research funded by the U.S. Department of Agriculture (USDA), Decker is attempting to use these traits to better puberty and fertility predictions in beef heifers.
“We were able to get a research grant from the USDA to collect traits from 5,000 heifers, focusing only on a small number of breeds. So, for this project we are focused on obtaining data from Red Angus and Hereford heifers and the data we collect will be added to a pre-existing data set of 6,000 Angus heifers,” explains Decker.
“We are still in data collection mode on this project, but so far, we have analyzed nearly 4,000 Red Angus heifers, which have been DNA tested for genomic enhanced expected progeny differences (EPDs) and possess pregnancy data through the Red Angus Association of America,” he continues. “Additionally, we have phenotype and pedigree information on the 14,000 other heifers which were part of their contemporary groups.”
Reproductive tract scores
The first trait Decker believes to be of value when attempting to improve genetic predictions is through a reproductive tract score, which exists on a one to five scoring system. According to Decker, this score can be given by a trained technician or veterinarian who palpates a heifer’s reproductive tract and examines the uterus and ovaries.
Decker notes reproductive tract scores are not subjective, instead they reflect biological and physiological changes experienced by the heifer as she undergoes puberty.
“Uterine tone and shape, ovary size and follicle size all change as a heifer approaches puberty,” he explains.
Decker also points out these scores have a significant relationship with pregnancy outcomes, as observed through the Show-Me-Select Program.
“Since most heifers with a reproductive tract score of one are culled, there are very few given the opportunity to go into a fixed artificial insemination (AI) program,” he says. “Of the small number of these heifers that do make it, only eight percent actually become pregnant as a result of AI.”
Decker continues, “We see the pregnancy rate go up dramatically in heifers with a score of two to 32 percent – but even this is disappointing for producers.”
Pregnancy rate shoots up to 46 percent in heifers with a score of three, 49 percent in heifers with a score of four and 52 percent in heifers with a score of five, according to Decker.
When it comes to pregnancy diagnosis, Decker notes data collected through the Show-Me-Select Program is achieved through ultrasound.
“There are a lot of different ways to get an accurate pregnancy diagnosis, whether it is through palpation, a pregnancy-associated glycoproteins (PAG) test, ultrasound, etc. However, the reason we focused on ultrasounding in this project is because we can identify bred heifers at the beginning of the breeding season, 45 days into the breeding season or anywhere in between or after,” Decker explains, further noting this information also provides fetal age.
“This is important for two main reasons,” he adds. “First, heifers who get pregnant earlier in the breeding season have a higher lifetime productivity compared to heifers bred late in their breeding season. These heifers tend to get bred at the beginning of the season for multiple years down the line.”
The second reason, according to Decker, is heifers bred early also have older, heavier calves resulting in more marketable pounds and a more uniform calf crop in terms of age distribution.
“Additionally, fetal age allows us to have a more quantitative measure of fertility outcomes in heifers instead of simply deeming them a success or failure,” says Decker. “We can use fetal age in two ways – days open and days to conception.”
Days open, as defined by Decker, is how many days a heifer is open during the breeding season. For instance, a heifer who failed to become pregnant in a 35-day breeding season would have an open observation of 35 days, while a heifer who got bred on the first day of the breeding season would have an open observation of zero days.
Decker further explains days to conception is the number of days it takes a heifer to become pregnant and is only observed in heifers which get bred.
As of Jan. 18, Decker’s research of the 4,000 Red Angus heifers showed a distribution of days open values from -21 to 250, a heritability of 11.6 percent for heifer pregnancy and a genetic correlation between heifer pregnancy and days open of 0.61.
Previous success in genetic improvement
Although Decker’s research is only in its beginning stages and he believes genetic predictions still have a long way to go, he notes there have been a multitude of previous successes in the beef industry when it comes to making genetic improvements.
“The beef industry has made genetic progress for growth traits such as birthweight, weaning weight and yearling weight, which are relatively easy traits to measure, record and report,” he notes. “One of the biggest benefits and something which has helped us get more accuracy out of these traits is we don’t analyze them separately. We combine these three traits, and the genetic effects shared between them is used to better predict all of the traits by combining them together.”
Decker also points out the beef industry has seen great success in improving calving ease in recent years, and although calving ease is a categorical trait – heifers either calve unassisted or with assistance – birthweight stands in as an effective indicator trait for calving ease.
“Nobody is getting paid on birthweight and nobody has a cost associated with birthweight. However, this trait allows us to more accurately predict calving ease genetics, which ultimately has an impact on a producer’s bottom line,” Decker states. “The real value of birthweight is it gives us a quantitative measure of things indicating calving ease.”
Decker continues, “Traditionally, carcass traits are also harder to predict, simply due to the fact once carcass traits are measured on an animal, the animal is no longer able to reproduce. Luckily, ultrasound data including intramuscular fat and ribeye area is a great indicator trait.”
“With all of this said, I would just like to point out with the wealth of genomic data we have today, as well as the ease and cost effectiveness of generating genomic data, I believe the time is really ripe to make a push toward improving the prediction of fertility traits,” Decker concludes.
Hannah Bugas is a corresponding writer for the Wyoming Livestock Roundup. Please send comments on this article to firstname.lastname@example.org.