Application of Novel Reproductive Traits to Genetic Evaluation
There is no denying the importance of reproductive traits in beef cattle, but improvement of such traits through genetic selection can be challenging. Data collection and herd measurement for reproductive traits are difficult and expensive, so advancement has been limited. In Australia, however, animal scientists have explored the application of novel reproductive traits for genetic evaluation, seeking to develop new selection tools for beef cattle breeders.
During the 2020 Beef Improvement Federation Symposium Online June 8-12, Matt Wolcott talked about how the novel traits were developed as part of a 14-year collaborative experiment by Australia’s government and beef cattle industry. As a scientist with the Animal Genetics and Breeding Unit of the University of New England, Wolcott was directly involved in the research that began with Brahman and tropical composite cattle, both of which have posted low cow reproductive rates under commercial production. More recently, related research has involved Bos taurus breeds.
According to Wolcott, the first novel trait defined was age at puberty for females, or the age at which a heifer commences the estrous cycle, as determined by ultrasound detection of the first corpus luteum. Age at puberty was found to be very heritable — 60% in Brahman and 50% in composites — with large variation within both groups.
“This suggests there is huge opportunity to apply selection to improve age at puberty,” explained Wolcott.
The second trait of interest was lactating anestrous interval, which is that period of time between calving and resumption of the estrous cycle, determined by detection of a corpus luteum. Lactating anestrous interval was also found to be highly heritable with significant variation within breeds. Wolcott called both female reproductive traits “accurate descriptors,” which should allow for relatively rapid progress in genetic selection.
“So we’ve got lots of opportunity to identify genetically superior animals, based on these reproductive traits,” stated Wolcott. “It’s also worth noting that age at puberty only affects first mating outcome (first-calf heifers), while lactating anestrous interval impacts rebreeding in lactating females every year. So lactating anestrous interval is probably the most important of the two traits.”
Looking at male reproductive traits, percent normal sperm was a trait found to have a moderately favorable genetic relationship with both of the female reproductive traits discussed. Wolcott called the correlation strong enough that percent normal sperm can be exploited as a genetic indicator of age at puberty and lactating anestrous interval in females. Decisions can be aided by published estimated breeding values for percent normal sperm.
Wolcott said further application of the novel reproductive traits is being taken to industry through the Repronomics Project, with application on greater numbers of cattle and more breeds, as well as crossbreds. Wolcott also said genomics will likely be the pathway to widespread application in the future, since reproductive traits are so expensive and expertise-intensive to measure.
To access the archived presentation slides and webinar session, >click here. For more information about this year’s symposium, including additional award winners and coverage of meeting, visit the Awards and Newsroom pages of BIFconference.com. For more information about BIF, visit BeefImprovement.org.
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