Bring in the Clones
The following commentary does not necessarily reflect the views of AgWeb or Farm Journal. The opinions expressed below are the author's own.
Sci-fi fans know the familiar image: sinister duplicates emerging fully grown from mysterious tanks, dripping wet, fully aware and definitely up to no good. Clones.
Setting fiction aside however, scientists have long recognized the potential for cloning technology to advance human medicine, biological research and even genetic selection in animals. Some scientists are seriously considering using cloning technology to bring back extinct animal species such as the woolly mammoth. In animal agriculture, cloning can replicate elite genetics, even after an animal has been slaughtered, processed and packaged.
Researchers at West Texas A&M University (WTAMU) have used that ability to clone an animal post-mortem, using DNA from muscle cells, to reproduce a rare and valuable carcass phenotype – cattle that grade USDA Prime and Yield Grade 1.
Presenting at the recent Academy of Veterinary Consultants (AVC) conference in Fort Worth, Texas, WTAMU Animal Scientist Ty Lawrence, PhD, described his team’s “Prime One” program, using cloning and crossbreeding to reproduce that rare combination of traits. Normally, marbling and yield are considered antagonistic traits. Cattle with the genetic potential to produce sufficient marbling to grade USDA Prime also typically produce a lot of subcutaneous fat. Carcasses that grade Prime usually rate at Yield Grade 4 or at best Yield Grade 3, due to excess outside fat and small ribeye area.
Carcasses that grade Prime and Yield Grade 1 represent about 0.03% of total fed-cattle slaughter, Lawrence says.
So the WTAMU set out to evaluate whether cloning could serve as a tool for improving marbling and yield simultaneously. “Can we produce taste fat without waste fat,” they asked. They searched for the elusive beast, and found a Prime, Yield Grade 1 steer carcass in a packing plant. They collected tissue samples and then worked with biotech company Viagen to produce a clone. This type of cloning involves removing the cell nucleus, containing the DNA, from a donor-animal’s somatic cell, such as a muscle cell. Scientists implant the genetic material into an oocyte or egg cell, from which they have removed the original DNA. Once the oocyte begins to develop into an embryo, they transplant it into a recipient cow, similar to conventional in-vitro fertilization and embryo transfer (IVF-ET) systems. The resulting clone calf is essentially a genetic twin to the original donor, just born at a different time.
The WTAMU team produced their first cloned calf, an Angus-based bull calf they named Alpha, in 2012. In addition to uncommon carcass traits, the original steer rated high for production traits such as feed efficiency. Around the same time, the team produced three cloned heifer calves, named Gamma 1, Gamma 2 and Gamma 3, also from Prime, Yield Grade 1 carcasses.
Once those calves matured, the team crossed Alpha with the three Gamma heifers using conventional IVF-ET processes, ultimately producing 13 calves. Of those calves, the group raised and finished seven steers, slaughtering them at an endpoint of .5 inches of backfat measured with ultrasound. Weighing an average of 1,225 pounds at slaughter, five of the seven steers graded USDA Prime, with one grading high Choice and the other middle Choice. The group overall rated 45% better than average for marbling, had 18% larger ribeye area and were 28% better than average for Yield Grade. All were either Yield Grade 1 or 2.
The research team now is engaged in additional tests, including a comparison of the cloned Alpha bull with top bulls from the Angus, Charolais and Simmental breeds. Using conventional AI, they’re mating the bulls to similar groups of cows and collecting data on multiple generations of calves raised in a commercial setting. They recently slaughtered the first groups of finished offspring from those matings, and the Alpha-sired calves ranked either first or second in every category and produced the highest value per hundredweight at slaughter.
The group also has begun evaluating progeny of Alpha/Gamma 1, the first male calf from the Alpha and Gamma matings and the first bull from two carcass-clone parents. These tests intend to determine whether cloning offers a viable tool for introducing desirable but uncommon traits and accelerating genetic progress in subsequent generations.
Cloning probably never will become a common breeding technique due to technical challenges and expense, and education will be needed to dispel negative perceptions among consumers. The technology could, however, help the industry improve beef quality and production efficiency by propagating the genetic potential of the very best cattle, even if those cattle are neutered or even slaughtered before anyone recognizes that potential.
AVC members can view recorded proceedings from AVC conferences on the AVC website. The next AVC conference takes place August 9 to 11 in Denver, Colo.
