By Raluca Mateescu and Aubry Pearce
Genomics is the field dedicated to exploring DNA’s structure, function, evolution, and genetic composition in animals. It encompasses the entirety of genes and genetic material present within an organism or cell.
Within the beef industry, genomic technologies have captured the attention of producers and attracted substantial research investments. These technologies are applied in various ways, with one common use being the selection of seedstock. However, genomics has also gained extensive acceptance in areas such as enhancing forage and feed grain breeding, developing diagnostic tests, creating vaccines, tracing the origins of food safety recalls, and serving various other purposes.
The Use of Genomic Tests in Cattle
DNA testing offers a range of applications within agricultural operations, encompassing assistance in bull and replacement selection, making informed breeding decisions, categorizing animals into specific management groups, verifying pedigrees, mitigating or eradicating undesirable genetic traits, and aiding in marketing efforts. Beyond the farm, DNA testing serves to shed light on evaluation processes, unravel the mysteries of both common and complex diseases, trace ancestral lineages, and contribute to forensic investigations by analyzing evidence.
However, the successful implementation of DNA testing on a farm hinges on having well-defined objectives before investing in such testing. The value of DNA testing within an operation varies and depends on factors like the cattle breed, the number of animals subjected to testing, whether the cattle are purebred or commercial, breeding objectives, marketing strategies, and the types of records maintained on the farm.
For instance, if your practice involves selling calves at weaning and your primary aim is to conduct DNA parentage tests to identify economically valuable sires (those producing calves with high weaning weights), but you aren’t consistently recording individual calf weaning weights, the efficacy of the test may be limited.
DNA samples for the majority of genetic tests can be collected from sources such as hair, skin tissue, blood, or semen. Sampling kits are available from laboratories or third-party providers, such as breed associations. These kits come with instructions on how to collect the sample and specify the necessary information to include with the sample, which varies depending on the specific test requested.
Figure 1. Schematic of sample collection using blood or tail hair for parentage verification. Credit: Felipe Alves, UF/IFAS
Genomically-Enhanced EPDs
Expected Progeny Differences (EPDs) serve as predictions for the average differences in genetic merit expected to be inherited by offspring. It’s crucial to consider the accuracy when evaluating EPDs. In the case of young animals, EPDs tend to be less precise since they have not yet produced any progeny. As more progeny are born and performance information accumulates, the EPDs for both the sire and dam become more reliable. Generally, bull EPDs are more accurate than cow EPDs due to the fact that the average bull typically has a larger number of offspring than the average cow.
Genomic testing offers a means to enhance the accuracy of predictions without the necessity of siring additional calves. Genomically-enhanced EPDs (GE-EPDs) can be generated for most beef breeds, substantially boosting the precision of EPDs. This enhancement is equivalent to incorporating performance data from seven to twenty-three additional offspring, contingent upon the specific trait in question. Consequently, producers can more confidently assess the genetic potential of progeny from young animals (such as heifers or yearling bulls) even before they have produced any calves.
It’s important to note that augmenting an EPD with genetic information does not guarantee that the EPD value itself will be more favorable. Instead, it primarily increases the accuracy of the EPD. For instance, a bull’s calving ease EPD may improve, worsen, or remain unchanged following a GE-EPD evaluation. The key distinction is that regardless of the actual EPD value, producers can have greater confidence that the bull’s calving ease will align with the EPD due to the heightened accuracy.
For individuals seeking to acquire bulls or replacement heifers, GE-EPDs should be employed in the same manner as traditional EPDs. The accuracy value specific to the trait in question will assist in gauging the expected level of variation.
Source : ufl.edu