The advantages and disadvantages of utilizing equine frozen semen are debated by stallion and mare owners alike. Will I continue to show my stallion or retire him to the breeding shed? Is there an international market for my stallion? What if my stallion is injured in an accident or suddenly dies? Is my mare a suitable candidate for breeding with frozen semen? Is it true conception rates with frozen semen are lower than those when using cooled semen? These are just a few questions to ask when considering whether to utilize equine frozen semen.
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What Exactly is a Dose of Frozen Semen?
Is a dose a breeding? Is a straw a dose? How many straws in a dose? How many sperm in a dose? These are often questions we hear from our clients when purchasing or using frozen semen. There is so much variability in the format of doses sold throughout the world that it can be confusing at times. To ensure you have the best opportunity of success when breeding your mare it is important to understand all the elements that determine an adequate dose of frozen semen. Here we review frequently asked questions that relate to what constitutes a dose of frozen semen.
Understanding Your Frozen Semen Shipment Transaction Report
Every shipment that we send from Select Breeders Services includes an envelope of materials, zip tied to the top of the frozen semen shipper, that provides information about the semen we are sending to you. Included in the envelope are the following items:
- Transaction Report
- Safety Notice for Handling Frozen Semen
- Thawing and Handling Instructions
- Info sheet on Management of Mares with Frozen Semen
- Return FedEx airbill and address label
- Info notice regarding tank rental and return
- Additional materials may include notices prepared by the stallion owner that they have requested us to include with the shipment, e.g. breeding and insemination certificates.
It Only Takes One...... Right?
How many sperm does it take to get a mare pregnant?
1 billion?...500 million?... One? Actually, any one of those answers could be correct under certain conditions. The only way to really answer that question is... "it depends". Fertilization is a complex process requiring that both the sperm and egg possess a myriad of functional attributes expressed at the right time and in the right place. A motile sperm is not necessarily a fertile sperm. So, how many sperm must be deposited in the mare for "acceptable" fertility? It would seem that this would be the logical basis for determining sperm numbers in an insemination dose for commercially distributed semen. To achieve the goals of both the mare and stallion owner it is necessary for each dose of semen to contain sufficient numbers of functionally competent sperm to maximize the probability of conception. The relationship between sperm number and fertility is expressed as a typical dose response curve (see figure1). However, the slope of the curve and the maximum level of fertility are different for individual stallions.
The Economics of Cooled and Frozen Semen
There are a number of misconceptions about frozen semen that are pervasive in the horse breeding community and one of them relates to the relative costs of frozen vs. cooled semen. We have heard horror stories of mare owners spending thousands of dollars purchasing and then trying to get mares in foal with frozen semen only to end the season with an open mare. Then there are also stories of stallion owners investing large sums of money freezing semen that is of poor quality or doesn’t result in pregnancies. Many of these nightmares are the result of lack of quality control on the semen that is put on the commercial market and/or proficiency of the lab or technician that is freezing the semen. Poor quality semen, whether fresh, cooled or frozen will result in wasted money, empty mares and unhappy breeders. This article will present objective information on the true costs of using frozen semen so that stallion and mare owners can make informed decisions.
Breeding Mares on Foal Heat
Breeding mares on their foal heat is a strategy used to maximize reproductive efficiency. Since income is generated from selling offspring, yearly foal production is critical to offset maintenance and breeding expenses incurred by the mare owner. With an average gestational length of 333 to 345 days, mares must become pregnant within one month post partum to continue producing foals each year. Mating mares on the first postpartum estrus is one method used to improve the chance of maintaining yearly foal production. Reviewing this topic for us is guest writer, Dr. Margo Macpherson with an excerpt from the chapter Breeding Mares on Foal Heat co-authored by Dr. Margo Macpherson and Dr. Terry Blanchard in the 2nd Edition of Equine Reproduction.
Preparing Your Mare For Breeding
There are many factors to consider before you breed your mare. This Q&A with reproduction specialist, Dr Karen Wolfsdorf of Hagyard Equine Medical Institute will help you be prepared. Questions answered include - Where do I start if I want to breed my mare?, Why do I need to get my mare examined by a veterinarian?, What does a pre-breeding exam include?, What can be done if my veterinarian finds a problem at the pre-breeding exam?, How should my mare be prepared for mating? and When do I find out if my mare is pregnant?
The Pros and Cons of 1 or 2 Dose Insemination Protocols
It is a common belief of many veterinarians and breeders that the lifespan of frozen semen within the mare’s reproductive tract is reduced compared to fresh semen. While no experimental fertility trials have been conducted to directly address this question the type of damage that can occur to sperm membranes during the freezing and thawing process theoretically could reduce the longevity of semen. Sperm binding to the lining of the oviduct can extend fertilizing capacity in the mare and there is in vitro evidence that frozen-thawed sperm do not bind as well to the oviductal epithelium. Therefore, it is generally accepted that the optimum time for insemination of frozen semen is in the period from 12 hours prior and up to 6 hours after ovulation. The timing of insemination is a good topic for debate and many mare owners and veterinarians have their preferred method of choice. Generally opinion is split between a one dose post-ovulatory insemination or a two dose timed insemination protocol. Dr. Sandro Barbacini of SBS Italia reviews the pros and cons of both options here.
The Facts About Frozen Semen and Post Breeding Uterine Fluid
The presence of fluid in the mare’s uterus after natural mating or insemination is a normal event that occurs in response to the breeding. This is the result of an inflammatory response that is needed to rid the uterus of any excess sperm or other contaminating agents. The influx of neutrophils (white blood cells) into the mare`s uterus after breeding results in the elimination of sperm, bacteria and other cellular debris and causes the release of prostaglandins, which stimulates uterine contractions. Typically the inflammatory response peaks 12 hours after breeding and by 24 to 48 hours the mares uterus is empty of fluid. However, some mares are more susceptible to prolonged retention of fluid and it may be retained for several days after breeding.