Production of hornless dairy cattle from genome-edited cell

• hornless phenotype of cattle are referred to as polled
• identification of variants associated with the polled trait through genetic analysis
• dehorning is a well established practice and currently the only immediate option for removing horns
• dehorning is necessary to reduce injury to handlers as well as the animal itself and animals around it

Aim:

- Identify and Isolate causative allele for polled.

- use genome-edited cell lines to produce hornless dairy cattle.

Gene therapy?

- unexplored

- isolate polled gene without genetic drag?

• Diagnostic PCR confirmed homozygous introgression of PC into 3 calves, with one introgression into a heterozygous calf

• No identification of any off-target introgression of the polled allele from sequencing the genomes of RCI-001 and RCI-002

• The animals were free of off-target genetic drag, demonstrating high specificity of TALENs for the POLLED locus

• First confirmation of a putative causative allele in livestock providing evidence that PC is causative for polled

Increases animals' welfare and decreases farmers' input

Production of hornless dairy cattle from genome-edited cell lines

Daniel F Carlson, Cheryl A Lancto, Bin Zang, Eui-Soo Kim, Mark Walton, David Oldeschulte, Christopher Seabury, Tad S Sonstegard & Scott C Fahrenkrug

Horned and polled cattle

PCR Analysis

• The identify of the polled genotype was analysed using diagnostic PCR
• The PCR products were also confirmed by Sanger sequencing

Carlson et. al, 2016

Results of the investigation

Debudding

Influence on the study

Painful and costly procedure

Dehorning

• Animal welfare concerns have lead to an increasing interest in dehorning not only by society but by the beef and dairy industry's.
• This has caused this initiation of study such as this one into the identification of polled genes
• Only painless solution is to breed out the gene entirely

• Estimated 80% of dairy cattle and 25% of beef cattle are dehorned every year
• Polled locus is fixed in beef cattle
• dairy cattle have lower frequency

Increased animal welfare concerns of husbandry practices

Carlson et. al, 2016

Contribution to Knowledge

The Study:

• Successful removal of calves' horns without painful and stressful procedures for the calf.

Kingvet Salem, 2015

But, why?

- dairy cattle with polled gene have lower milk production

- $252 lost per lactation

- Due to genetic drag, admixture of unideal genetic material

Noy, 2015

Applying This Research

Approach:

- Transcription Activator-Like Endonucleases (TALENs)

- Highly specific gene cutting

- eliminates admixture

• Elite Dairy Bulls

• Produce homozygous polled (PP) clones of the high quality bulls

- Isolated allele inserted in bovine embryo fibroblast genomes

- 4 cell lines cloned (Somatic Cell Nuclear Transfer)

- 3 full term pregnancies, 5 calves

Hug, 2015

BABS Polled Blonde, 2015

Every calf born from that bull will be polled

Justification

GeneCopoeia, 2016

Improving the health and welfare of cattle

Neuroskeptic, 2010

The Progressive Dairyman, 2015

QUIZ

Question 1: What industry will be affected most by the results of this study?

Question 2: What initiated the the study?

Question 3: What is the main issue surrounding selective breeding that makes it an ineffective way to produce polled dairy cattle?

Question 4: What did they amplify in the PCR test?