Old bulls bring forth new genetic benefits

Animal genetics plays a crucial role in modern agriculture, improving food sustainability and animal adaptation to climate change. Over the years, animal breeders have emphasized the importance of genetics in improving animal productivity. Preserving diverse sources of animal germplasm is critical to maintaining genetic diversity, which provides economic sustainability and food security in the face of new diseases and climate change, and advances our understanding of animal genetics and genomics.

Germplasm research
National Animal Germplasm Program coordinator Harvey Blackburn and technician Ginny Schmit.

The USDA Agricultural Research Service’s National Animal Germplasm Program (NAGP) has collected and stored more than one million samples from more than 64,000 animals in the United States. These samples, dating from the late 1940s to the present, aim to maintain the genetic diversity of American livestock by providing genetic security and a better understanding of the genes that influence and control valuable animal characteristics.

“Over the past 24 years, NAGP has released nearly 11,000 samples from its germplasm collection to farmers, academic researchers and others in the animal industry and scientific community for molecular studies and the introduction of lost genetic variability into living populations,” said Harvey Blackburn, NAGP animal geneticist and program coordinator. “The released genetic resources allow for the exploration of important problems facing the livestock industry.”

Recently, the use of NAGP collections has brought to light interesting discoveries.

A beef cattle breeder in South Dakota has successfully incorporated samples from the NAGP filing into their breeding program. They requested and received semen samples from five Angus bulls born before 1997 that were used to mate with over 150 Angus cows. The resulting offspring help modify the farmer’s herd of cows to meet his production and marketing goals. Progeny of sires from pre-1997 genetic resources have shown high performance levels for a combination of traits and have been consistently highly sought after in the marketplace in recent years. Researchers from NAGP and the Livestock and Range Research Laboratory are now studying the underlying genomic differences in the progeny of these over 26-year-old bulls and the current Angus population to better understand the basis for the higher performance levels.

This isn’t the first time NAGP animal geneticists and the industry have seen the positive impact of sampling the older generations of bulls in the collection. In 2020, Blackburn collaborated on a study completed by researchers in the Pennsylvania State University (PSU) Department of Animal Sciences. In that study, it was found that the entire U.S. Holstein population came from two paternal lineage lines (just two different Y chromosome origins) traced back to prominent 1970-era sires. Through tracing the genomic and genealogical lineage of the samples in the germplasm collection, found two additional and unique Y chromosomes that have been lost in current Holstein lines due to selection. The calves were created using germplasm samples from these two bulls and, as in the Angus example, the daughter progeny produced milk yields above the expected level and on par with their counterparts from the current Holstein genetic base born in the same year.

“These examples of how animal germplasm collections are used in research and breeding programs are of great importance to the industry,” Blackburn says. “Although large breeds of dairy and beef cattle, such as Holsteins and Angus, are thought not to have diversity issues, these examples found otherwise, especially with the lack of Y chromosome variation in Holstein bulls. Both examples Angus and Holstein illustrate the value of germplasm harvesting for expanding, and even saving, genetic diversity, improving animal performance, and suggesting to scientists that there is still significant research to be done to understand the genetic basis of livestock performance.” .

The NAGP gene bank also includes samples of aquatic animals (fish and crustaceans), poultry and insect populations. Animal germplasm requests can be submitted to the USDA Agricultural Research Service NAGP at Animal-Germplasm Request (usda.gov).

The Agricultural Research Service is the primary internal scientific research agency of the United States Department of Agriculture. Every day, ARS focuses on solutions to agricultural problems affecting America. Every dollar invested in US agricultural research translates into a $20 economic impact.

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