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How to maximize embryo transfer programs in commercial dairy herds

Shantille Kruse, Ph.D. for Progressive Dairy Published on 19 June 2019
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When doing anything to scale, it is key to look for critical points where efficiencies can be maximized to ensure the most value for your dollar.

One of the benefits of working a donor group within a large herd, is a bigger pool of donor candidates from which to select.

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Donor selection

Genomic testing is the first tool to determine which females would make the greatest impact on a herd’s genetic potential. Typically, that number falls somewhere between 5% to 10% of the population. 

To truly focus on being cost-effective, another screening measure to consider is antral follicle count. Antral follicle count is simply the number of follicles visible on the ovary using ultrasonography at any given point in her cycle (except for day of estrus). While antral follicle count is variable among a population of cows, it is very repeatable within an individual and is positively correlated to the number of oocytes a donor will produce.

Having your veterinarian scan ovaries, and thereby selecting the top half of potential oocyte producers, will greatly improve efficiency. The rate-limiting step in the equation of how many embryos can be produced is the number of oocytes the lab starts with, so this parameter helps to eliminate the poor performers. Additionally, antral follicle count is moderately heritable. Therefore, on average, when selecting high-oocyte-producing dams, their daughters are more likely to also make more oocytes. 

Treat your donors like donors

Once the population is selected, donors should be housed in one location in small groups by age. This will facilitate monitoring their health and diet, as well as giving follicle-stimulating hormone (FSH) shots in a timely manner. It will also make it easier to move them to the collection area on day of ovum pickup (OPU). If donor housing and allocating labor to manage donors isn’t feasible on your dairy, consider a donor housing facility where dedicated staff can ensure best care for the elite animals. 

Give them FSH

The positive impact of FSH on oocyte numbers and quality has been published numerous times. It has also been demonstrated that stimulation and synchronization are necessary to collect a group of oocytes that are at the same stage of development. This gives them the greatest opportunity to become an embryo and, eventually, a pregnancy. 

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The American Embryo Transfer Association (AETA) collects embryo production data each year. The most recently published information shows that dairy donors collected without FSH make an average of 2.3 viable embryos per collection (47,018 donors collected) versus 5.2 when FSH is used (36,724 donors collected). So you’d have to collect a donor and pay for the consumables and the aspirator 2.3 times when not using FSH compared to a single collection with FSH, taking more time to make genetic progress. Collecting donors with FSH is simply more efficient. 

Be flexible on sire selection

Just like donors, some bulls result in higher embryo development than others. IVF labs keep track of embryo development by bull, and it is typically repeatable. When selecting sires, ask for that information from your service provider, and use it in your decision-making process. Regardless of their genetic merit, avoid using bulls that have below-average performance, as such choices will greatly impact how cost-effectively you’re able to create embryos. If a bull hasn’t been used before, some labs may also be able to test bulls on slaughterhouse oocytes before using them on donor oocytes to optimize performance.  

Recipient selection and setup

Once the donors are collected and sire selection is made, they are sent to the lab to create embryos that will be transferred eight days after donors are collected. Just like with donors, very good animal care is essential to ensure optimal pregnancy rates. 

Recipient synchronization does not need to be complicated, it can be as straightforward as a double shot of prostaglandin. Alternatively, you could simply continue with the normal synchronization method your dairy uses for A.I., but instead of breeding, just hold those heats over as recipients.  

Embryo transfer

Once embryos are created, there are two options: have them sent to your dairy for fresh transfer or keep them at the lab for freezing for later transfer. Having a frozen embryo bank to transfer is ideal in cases where more recipients are available than embryos. However, processing embryos for fresh transfer is generally less expensive than freezing, and a greater percentage of embryos are acceptable for transfer versus freezing, making fresh transfer the more commonly used method on large dairies. 

On day of transfer, an incubator will arrive with fresh embryos in small tubes. The veterinarian will assign a grade and stage to the embryos, and load them into straws for fresh transfer. On some large dairies, veterinarians who transfer these embryos work alongside nonveterinarian employees who are trained in embryo transfer procedures. 

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The American Veterinary Medical Association policy on embryo transfer procedures states they are a function of veterinary practice due to the need to diagnose, pharmaceuticals involved and potential need for surgery. It also notes that nonveterinarians should work under the supervision of a veterinarian. However, individual state practice acts differ on who can perform collections and transfers and if a veterinarian’s supervision is required.  

The following states have specifically made embryo recovery and transfer exempt from their veterinary practice acts: Arkansas, Georgia, Kentucky (if the individual has a graduate degree in reproductive physiology or practiced in Kentucky from 1987 to 1992), Montana (under supervision of a veterinarian), Nebraska (if the individual is an owner or has a graduate degree in reproductive physiology), North Dakota (if the individual is an owner), Ohio (if the individual is an owner or designated by the owner under the direct supervision of a veterinarian), Tennessee (if the individual is an owner) and Wyoming (if the individual is an owner or employee).  

Regardless of who performs the transfers, any embryo transfer program should be overseen by a veterinarian, preferably one certified by the AETA.  end mark

Shantille Kruse is an IVF liaison with Boviteq.

PHOTO: Commercial dairies looking to create more cows with the genetics they desire may consider in vitro fertilization (IVF). Following a few pieces of advice can increase the success and return on investment of this reproductive technology. Staff photo.

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