Zoetis has developed the first complete Holstein de novo reference genome,
giving geneticists the ability to map regions of the genome influencing a range
of health and disease outcomes. This significant development will promote
advancement of the dairy industry through healthier, more productive animals.
The genome was completed with several new technologies and three sequencing
platforms to order the Holstein genome as accurately as possible. With this
level of accuracy, scientists can more easily identify genes that advance herd
health and productivity and, alternatively, those genes that impede the dairy
industry's progression.
"Sequencing a genome is the most important step toward fully understanding
it," said Sue DeNise, PhD, executive director, Zoetis Animal Genetics
Global Research and Development. "In the future, discoveries made from the
new Holstein reference genome will allow us to identify new targets for disease
resistance and utilize natural selection processes to improve health and
welfare of cattle," DeNise said. "It's like going from analog TV to
high-definition TV. We'll have even better insight into which genes reside to
help animals resist and withstand diseases, such as pneumonia and
mastitis."
Until now, the dairy industry looked to the first reference genome assembled
for cattle in 2009, which was derived from a beef cow named L1 Dominette 01449,
a Hereford born in Montana. While Dominette's genome assembly piloted the
cattle genomics era, a single reference genome was not enough to demonstrate
the full genetic differentiation of a species. Genetic makeup fundamentally
differs from breed to breed due to genetic drift and selection due to breed
divergence. Comparing a Hereford genetically with other breeds of cattle - such
as Holsteins - was only the beginning.
Genome sequencing is often compared to decoding a software program. The process
determines the order of DNA bases in a specific genome - the order of A's, C's,
G's and T's that together make up an organism's DNA. Cattle have 30 pairs of
chromosomes and about three billion bases to put into order. To facilitate a
highly accurate sequence, a single Holstein bull was utilized from straws of
semen available commercially. These samples from a single animal contain the
entire DNA blueprint for an animal, providing unique insights into the Holstein
breed.