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Veterinarian View | December 2023

Considerations for Embryo Collections on Heifers

contributed article by Dr. Vince Collison, Collison Embryo and Veterinary Services,

Rockwell City, Iowa



One of the things we recently have been asked about by several clients is, “What do you think about collecting a heifer?” While there is really no right answer, there are several things to consider based on our experience of collecting heifers. With either IVF or conventional flushing, we recommend that the heifer has had at least two natural heats before proceeding.


Conventional Collections

We have performed conventional flushes on virgin heifers with good success. You improve your odds of success by having the heifer well grown out and in a normal body condition. We have conventionally collected some show heifers that are over-conditioned, and this can be detrimental to superovulation response. Also, when heifers are over-conditioned it can make the collection process more difficult to perform.


As mentioned before with cows, if the heifers are on a high concentrate ration, it can also have a detrimental effect on the superovulation response. Try to have it so the heifers have access to grazing or grass hay to increase their fiber intake. Energy derived from fiber versus concentrate seems to work the best.


Show Heifer Issues

Often the heifer that is to be flushed is a show heifer. One of the issues we’ve found is that when they are stimulated with FSH they will tend to want to shuck hair, which can be very counterproductive when trying to get a heifer ready for a targeted show.


The other issue is that the heifers will go off feed sometimes or at least not eat as well. This is probably due to getting the heifer off her routine from getting injections twice daily during the setup process. Also, the ovaries are going to swell up during the superovulation process and this probably causes some abdominal discomfort to the heifer.


Single Egg Flushes

One way we have gotten around this is to do single egg flushes on show heifers. Basically, there is no superovulation done to the heifer, but when she comes into a natural heat we go ahead and AI her and then collect the single embryo. This has worked very well to at least get something going on a show heifer with minimal risk of her shucking hair and getting her out of her routine.


We have found embryos collected from single egg flushes to have very high pregnancy rates. This helps compensate for the expense involved with going after a single embryo. We have found that the recovery of a single embryo is higher if performed eight days after the standing estrus rather than seven days after heat as done with simulated cows.


Also, we have found that the embryo collected on day eight tends to have the same development rate (stage) as an embryo collected from a stimulated cow on day seven. So do not be concerned with the embryo being too advanced when collecting at day eight on a non-stimulated collection.


Risks

The other thing about collecting a show heifer is there is always the risk of something going wrong. Although it is rare, there is always the possibility that there could be an infection from blocking the tail or an injury occur while in the chute for collection, to name a few. So, it is important to weigh the risk of something going wrong versus the reward of getting something started early on a show heifer. My personal opinion is to give the heifer the very best chance of doing well in the show ring, it is best to wait to perform collections after the show career is over.


IVF Collection

The other option for collecting heifers is IVF. Producers will often want to pursue this option on heifers rather than conventional flushing. It is probably a good option for a heifer that is going to be sold in a sale and the owner wants to collect embryos prior to selling her. We have found that collecting these younger open heifers probably result in lower-than-average numbers being collected.


Also, pregnancy rates on these embryos might not be as high versus if the heifer was a little older. Many of these collections are performed as non-stimulated aspirations, so possibly stimulating prior to collection would help to improve that. Probably a better option on heifers is to get the heifer pregnant first before performing any IVF collections. It varies heifer to heifer, but generally we can collect them via IVF until they are around 100 days pregnant.


Sticking to a Schedule

To me it is a priority to get the heifer pregnant on schedule, so she calves at your targeted calving date. If you are wanting to collect a heifer prior to breeding and then she doesn’t get pregnant on schedule, there is always the issue of did collecting her push her back or is it really a case of the heifer was pushed back because of her lack of inherent fertility or just poor timing on AI, etc. This is probably even more of a concern when doing conventional flushes on virgin heifers.


This is where I feel getting a heifer pregnant first and on schedule is the bigger priority and then we can come in later and collect oocytes while she’s pregnant with IVF and still get some calves on the ground for next year out of the heifer. This is probably also a good option for someone that still wants to collect a show heifer. She will be bred up on time so she will look the part in the show ring and IVF can be performed without stimulation to reduce the risk of shucking hair.


If you decide to collect embryos from a heifer these are some of the things to consider. As stated earlier, there is no right answer but we’ve learned from experience what may go wrong, especially when it comes to show heifers. For some operations it is important to collect from heifers before they are sold, but maybe expectations for results may need to be lowered for younger heifers.


If you are wanting to collect a replacement heifer, consider using IVF so that you can get her pregnant on time for her to calve with the herd. Then you can collect the heifer after she is 30 days pregnant. IVF is perfect for donor heifer collections because it gives you the best of both. Your donor heifer can calve on time and yet you can get some embryo progeny that are born within one to two months after the donor calves.



Dr. Vince Collison is co-owner of Collison Embryo and Veterinary Services PAC

in Rockwell City, Iowa.

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