RESEARCH IS ESSENTIAL TO A SUCCESSFUL E.T. PROGRAM
by: Stephen B. Blezinger
In the last issue we began an extensive discussion of the basics of embryo transfer
in the beef cattle industry. In this issue, we'll continue and complete this
discussion by examining a number of issues surrounding the use of technology
as well as its overall effectiveness and efficiency.
Donor Selection - one more time
In the previous issue we briefly discussed some of the consideration for selecting
the donor cow. The most significant of these factors being selecting an animal
of superior genetic make-up. What does this mean, exactly? What is superior
genetic make-up? Is this a cow that has done really well in the show ring
and exhibits excellent conformation and eye appeal? Is she an animal that
has shown outstanding muscling, weight gains, feed efficiencies, ultrasound
ribeye area? The answer to this is, all of the above. These are all important,
economic traits that can be evaluated before the animal is even close to
breeding age. But then other production characteristics must be considered
in a donor prospect. What is her milking ability, expectation of calving
ease, reproductive capability - not just producing eggs and embryos but actually
carrying a calf to term. Also, how are her heifer and bull calves going to
After the last issue I received a couple of calls concerning this topic. One
in particular was from a client of mine - Louis Duke, general manager of
Indian Valley Ranch in Dover, Arkansas. Louis has been involved in all phases
of breeding for years. Indian Valley has an aggressive A. I. and ET program
so I have long respected Louis' experience and knowledge in this area. He
pointed out that in many cases cows that showed exceptional performance potential
when they were young and thus were donor prospects did not turn out quite
as well once they were actually placed in an ET program. He cited numerous
cases where donor cows, while producing quality embryos, were substandard
in any number of other areas including the ability to carry a calf to term,
milk production and so on. Also, in many cases, the embryos these cows produced
resulted in calves that were not of the expected quality. Granted, the bull
used plays a large role in the quality of the calf but this is still a factor
in the value of the cow as a donor.
The whole point here is that donor cows must be selected carefully and evaluated on a great deal more than how she performs in the show ring.
It has been suggested that donor cows should be selected based on the following criteria (Selk, 2004):
1) Regular heat cycles commencing at a young age.
2) A history of no more than two breedings per conception.
3) Previous calves were born at approximately 365 day intervals.
4) No parturition difficulties or reproductive irregularities.
5) No conformational or detectable genetic defects.
Donor and Recipient Management
Every ranch or ET technician has their own "recipe" or protocol for the management
of their ET program. The various management practices used can have a significant
effect on the efficiency and effectiveness of the overall program. As the
old saying goes "the devil is in the details." This is very much true for
the actual superovulation/collection process and it is also true here where
the work is done to properly prepare both donors and recipients for an effective
Sound nutrition is absolutely essential for a successful ET program. Remember that nutrients provided to an animal are prioritized. In other words, there is a specific order in which nutrients in the body are used to supply all the physiologic processes. Reproduction, in most animals including cattle is last on the list since it is not required for the survival of the animal. As such, if any nutrient is in short supply, the reproductive system will fall short first and thus performance will be compromised.
Unfortunately in some cases producers and technicians alike have been known to over-do the nutritional program which can be very counter-productive. The feeding and nutrition needs of cattle in an ET program must meet a single goal: effectively providing for the nutrient needs of a specific animal or group of animals to maximize reproductive efficiency. This means meeting ALL the nutrient needs but not providing these nutrients in significant excess. Excesses of any nutrient typically results in an imbalance and nutrient ratios that can create problems, i.e. too much protein relative to energy, too much of one mineral as compared to another. The word to keep in mind here is balance.
While it is critical to provide optimal amounts of all nutrients (protein, energy, minerals, trace minerals, vitamins), this needs to be done in a proper balance. It may be useful to provide a small amount of added nutrient to insure that all the bases are covered but, as mentioned, excess is not a good thing. Protein is required to tissue and muscle development as well as the synthesis of hormones and reproductive tissues. Excessive protein creates a situation where the extra nitrogen must be cleared from the system and thus creates a load on energy usage in the body. Plus the excess nitrogen also creates problems for other physiologic processes. Energy intake needs to be positive. She needs to be gaining weight, not losing. Cows with body condition scores (BCS) from 5 to 7 (moderate to good flesh) out of 10 are preferred. Over-fat (BCS >8) cows generally create problems and should be avoided.
Minerals and vitamins should be well balanced with attention paid to the ratios
of one to another. In many cases producers will find a mineral/vitamin supplement
with all the bells and whistles they can to feed to donor cows. If the additive
indicated does not have sound research backing it's use do not waste the
time and money that it costs. As always go back to sound, well researched
nutritional knowledge when building this part of your program. Consult a
nutritionist for help with your program to insure it is properly balanced
and to account for the variation that is always present between one operation
When designing your overall ET program do not stop with the donor cows. While with recipient cows you are not concerned with the superovulation process, the recip has to be under the same nutritional plane to insure she is reproductively sound. It is important that recips conceive as efficiently as possible, the
first time, when embryos are implanted. Maximum breeding efficiency is the goal when placing an expensive embryo in a recip cow.
As with nutrition (and related to it), animal health must be good. It is important that both the donor and recip cows are in excellent health, with no illnesses or infections present. This also includes injuries, internal and external parasite loads, etc. It is important to minimize any stressful condition that could reduce the animals reproductive performance. The producer will want a complete, aggressive, herd health program in place to insure any potential health challenge is addressed. Work with your regular herd veterinarian as well as the ET vet or technician to insure all potential health issues have been addressed.
Reducing stress in the donor and recipient is important to insure good reproductive performance. Stressful situations that can affect donor and recipient cattle can include:
• Environmental (heat, cold, excessive moisture, drought).
- poor or poorly designed facilities, use of cattle prods, dogs, lot of noise
- insufficient nutrients regardless of type.
- illnesses that have not been addressed, foot problems, parasite loads.
Transportation - cattle must be hauled a long way to the ET facility.
While it is impossible to eliminate stress, it is important to minimize these as much as feasibly possible.
The costs of embryo transfer are as variable as the costs of buying a new television
or automobile. Many different options and packages are offered by embryo
transfer technicians. Some technicians perform embryo transfer only on the
farm or ranch where the donor cow is located. Others have facilities to house
and board donor and recipient cows and perform embryo transfer under hospital-like
conditions. Many technicians have the equipment and expertise to freeze and
store embryos for later transplantation or shipment around the U. S. or to
other countries. Minimum costs of $250 per pregnancy have been reported by
embryo transfer technicians. These costs may not include drug costs for superovulation,
and certainly do not include semen, registration, embryo transfer certificates,
blood typing of donor cows and ancestors, and most importantly the cost of
maintaining the donor cow until the calf is weaned. Three to five straws
of valuable semen can be priced from $45 to $300 (also highly variable).
Proper nutrition, health care, and synchronization of the donor and the recipient
can add another $400 to $500 expense to each successful pregnancy. Consequently,
many purebred operations conducting embryo transfer on a regular basis consider
that each "ET" calf must have a market value of $1500 to $2000 greater than
other naturally conceived and reared calves in the herd before embryo transfer
is considered. Table 1 provides an illustration of costs and calculates cost
per embryo at different embryo production/collection rates.
|Table 1. Estimated costs of producing frozen embryos for future transfer*
|Table adapted from Grimes - Ohio State University
*These costs do not include donor expense, labor, or overhead.
As you can see, the use of ET can be an expensive proposition. A concept that is growing in popularity is the use of cooperator herds. A cooperator herd is a location used to place the embryos from a breeder's donor(s), the calves are born and reared, then purchased back at weaning time. A premium over current market prices is paid to the cooperator for his extra labor and management. This arrangement allows the breeder to lower his overhead costs by reducing the number of cows owned and being maintained. Depending on the agreement between the breeder and cooperator, ET calves from cooperator herds can cost $650 - $900. Potential negatives associated with this practice include poor performance of embryo calves due to lack of desired management and increased exposure to new disease not found in the breeder's herd.
Along with the development and evolution of embryo transfer have come an assortment of related technologies that have merits of their own. A paper by Dr. Roger Davis illustrates the following:
Embryo Sexing. Embryo sexing requires that a small biopsy be removed from the embryo and analyzed using DNA technology to determine the sex. This technology is considered cost effective and is utilized quite commonly in dairy cattle. On average, the pregnancy rate with frozen-sexed embryos is slightly lower that non- manipulated embryos. The procedure is quite tedious, time consuming and adds cost to frozen embryos. It's use questionable as to it being cost effective in beef herds. The biopsy also penetrates the zona pellucida (shell) which yields the embryos non exportable to some countries.
Ultrasonography. This technology is used commonly to evaluate ovaries, detect early pregnancy (27 days), and determine the sex of the fetus (55-70 days gestation). Ultrasound is a very useful tool and can help utilize recipients more efficiently by early pregnancy testing and re-use of open recipients. Examining the ovaries of donor cows and recipients can also be useful in determining if the ovaries are functioning properly. Ultrasound is an excellent tool to use in general reproductive examinations as well.
Embryo Splitting has been used more commonly in the past. It is used to produce identical twins. The number of calves from a given number of embryos can be increased, however twice as many recipients are needed and the pregnancy rate is decreased. The high cost of recipients makes this technology questionable from an economics standpoint.
In-Vitro Fertilization, (IVF) is basically "test-tube calves". This procedure is quite effective in producing embryos, however the pregnancy rates can be disappointing and the abortion rates are high with high incidence of giant calves which leads to low numbers of healthy live calves. This technique is practical for very valuable cows that will not reproduce using conventional ET. Frozen IVF embryos yield varying and mostly disappointing pregnancy results.
Cloning uses ET as part of the process to produce pregnancies. This technology has greatly improved and is restricted to research and very valuable animals such as transgenic animals like Dolly the sheep that are used to produce rare pharmaceuticals. In Canada there are presently restrictions on selling production (semen) from cloned or genetically modified animals. The issues surrounding the use of cloning technology are extensive and will continue to evolve.
Embryo Transfer can be an excellent tool for production of superior genetics. However, given the complexity and expense it should not be entered into without extensive thought and research, especially in selection of donor animals. Many good embryo transfer veterinarians, technicians and companies in general are found across the country that can help the producer begin use of this technology. Talk to several of these before making a final decision.
Dr. Steve Blezinger is a management and nutritional consultant with an office in Sulfur Springs, TX. He can be reached at 667 CR 4711 Sulphur Springs, TX 75482, by phone at (903) 352-3475 or by e-mail at firstname.lastname@example.org. For more information visit blnconsult.com.