Reports from the world of equine research.
Another cloning milestone has been reached by researchers at Texas A&M University with the successful birth of a foal produced using oocytes from a live mare.
Mouse, was born May 5, 2010. The efforts of his owner, Kit Knotts, to find a horse that had the same qualities as her prized Lippizaner stallion Marc, (Pluto III Marcells) led her to Texas A&M University and equine reproduction expert Dr Katrin Hinrichs.
Written by Mark Andrews.
Published online 19.06.10. Updated 26.02.10
© Copyright Equine Science Update 2010
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“We have actually worked on this clone for about two years,” said Hinrichs, a professor in the Department of Veterinary Physiology and Pharmacology. “ This is actually our first foal produced using oocytes, or egg cells, from live mares. We recovered the oocytes from our herd of research mares using the same method used to recover eggs from women for in vitro fertilisation. We used the oocytes for the cloning process, which made it difficult as we had very few to work with at any one time. During the cloning process, we tested a new technique that has been reported in mice to decrease birthing problems.”
Dr Hinrichs lab is noted for achieving the first cloned foal in North America, and the third in the world with Paris Texas, who arrived in 2005. The lab has since produced twelve cloned foals.
The process began with a biopsy of skin cells from Marc, the horse to be cloned. Through the cloning process using oocytes recovered from a live mare, viable embryos were developed and sent to Hartman Equine Reproduction Center, an embryo transfer facility in North Texas which works closely with Hinrichs’ lab, for transfer into the surrogate mares. Minnie, the mare carrying Mouse, stayed in North Texas for approximately 200 days, then was sent to her new home in Florida.
Minnie began to show signs of an early delivery, and was taken to the University of Florida College of Veterinary Medicine for observation and intervention. That’s where Mouse arrived and was cared for by a team of neonatal experts that helped make sure he would make it through this critical time.
What problems might be expected with cloned foals?
In an article in the Journal of the American Veterinary Medical Association, Dr Aime K Johnson and others from Dr Hinrichs’ lab examined their records relating to cloned foals born between 2004 and 2008.
Fourteen cloned foals were born alive. Six of these were clinically normal for all variables that were checked. These included gestation length, birth weight, foaling complications, gross abnormalities of the fetal membranes, appearance of the umbilicus, mental state of the foal, limb deformities.
Eight foals did have problems. Most common were maladjustment, enlarged umbilical remnant and angular deformity of the forelimbs. Some foals required aggressive treatment and intensive care. Two foals died, but all the others responded to treatment. All twelve foals that survived have remained healthy.
Because of the risk of complications and problems in the period just after birth, Dr Hinrichs’ team recommends that foals derived by cloning should be treated as high-risk neonates, and their birth should be closely supervised. Facilities for intensive care should be available in case they are needed.
They suggest that supplementary oxygen should be on hand. Plasma transfusion may be required, as failure of passive transfer of immunity is frequently a problem -even when the mare’s colostrum quality was adequate. The umbilicus must be monitored closely and treated aggressively should signs of infection appear.
Once past the critical first few days of life, foals derived by cloning appear to be healthy and can be expected to grow normally.
For more details see:
Physical and clinicopathologic findings in foals derived by use of somatic cell nuclear transfer: 14 cases (2004–2008)
AK Johnson, SC Clark-Price, Y-H Choi, DL Hartman, K Hinrichs.
JAVMA (2010) 236, 983-990
Photo showing a common abnormality of cloned foals. Typically the umbilicus lacks the
natural breaking point and is thickened and edematous. This foal did have to have his umbilicus removed at about a week of age.
Photo courtesy Dr Aime Johnson
Mouse meets Marc. Photo courtesy Texas A&M University