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Mares can develop problems during pregnancy or be at high risk of losing the pregnancy for a variety of reasons. These include age (old mares frequently have endometriosis in which the uterus is unable to properly supply the fetus with appropriate blood supply and nutrients), physical conditions (placental and fetal fluid abnormalities; body wall tears; chronic debilitating conditions such as laminitis and Cushing’s disease), and acute disease or injury (placentitis, uterine torsion, surgical colic, colitis, acute laminitis, or fractures). When a mare becomes stressed or debilitated, inflammatory chemicals and prostaglandins increase and induce abnormal uterine contractions and potential pregnancy loss. Reproductive problems that arise during gestation, however, when detected and diagnosed early, can still result in the survival of the mare and usually the foal. The abnormalities most commonly seen during the middle to late stages of pregnancy will be discussed in this article.

For veterinarians and technicians accustomed to inseminating fresh or cooled semen in large (20-60 ml) volumes, the idea of inseminating 0.5 to 4 ml of thawed frozen semen can be intimidating.  During processing, frozen semen is concentrated by centrifugation and is typically packaged in small 0.5 ml straws at a sperm concentration that is often as much as 5 to 10 times greater than cooled semen. Therefore, a full insemination dose of frozen semen may be contained in just a few milliliters of volume whereas the same number of sperm extended for cooling may require 30-40 ml of volume.

The horse genome contains all the information required to direct the growth and function of a foal, from conception to death. This enormous “text” is organized into chromosomes, much like the volumes of an encyclopedia. The domesticated horse possesses 32 unique chromosomes, and most cells carry two copies of each chromosome for a total of 64. Gametes of course are the exception, carrying just one of each of the chromosome pairs to the future offspring. This article will discuss information about genotype vs. phenotype, genetic testing, and recent genetic studies performed on stallions.

Whether a mare is maiden, recently foaled, or barren can influence her ability to conceive when breeding her with frozen semen. The first pregnancy obtained by using frozen-thawed semen in the equine species dates back to 1957 and was obtained using epididymal semen. However, for many years this reproductive technology has achieved limited progress in the horse compared with other species such as cattle. This was mainly because for a very long period of time only a few horse registries allowed the use of frozen-thawed semen. Hence, economic interests and resources allocated to research have always been minimal and as a result obstructing advances in this area.

By now, most people in the breeding industry know what embryo transfer (ET) is however there is still a little confusion or misconception. I would say that the increased use and knowledge of in vitro fertilization, popularly referred to as ICSI (Intracytoplasmic Sperm Injection), has led to some of this confusion. We hear people interchanging the words embryo and egg as if they are the same thing. Let’s take a minute to draw a simple distinction between the two procedures.

Older mares have a knack for being the sweetest and gentlest mares on the farm. We see them year after year, either carrying their own foals or returning to donate embryos if their reproductive status requires. Oftentimes, these mares are considered “special” patients, requiring a unique combination of diet, exercise, and metabolic support to maintain their physical and reproductive health. We often see older performance mares that are being bred for the first time following a long and successful show career. Reproductive problems such as cervical adhesions and uterine infection can be common in older mares which affect their ability to carry a foal or donate an embryo.

Dr. Glenn Blodgett is the horse division manager at the 6666 Ranch, a member of the SBS Affiliate Laboratory Network and the current president of the American Quarter Horse Association. In recent years, Dr. Blodgett has implemented the use of chemical ejaculation with one of the stallions in his care. In this article, he will share with us in what situations chemical ejaculation might be useful, recent research performed using the procedure, how he uses it in his breeding program and the success rate of his attempts.

The test freeze is the first freeze performed on a stallion when he comes to a Select Breeders Services (SBS) Affiliate Lab to have semen frozen. We primarily have four different semen freezing protocols that we test on each stallion. The differences between each protocol being in either the extender formulation or the rate of cooling. For subsequent freezes we choose the protocol which gives the best results as determined by post-thaw motility. Regardless of the protocol, once the straws of semen reach -120 degrees Celsius in the programmable cell freezer they are then plunged into a bath of liquid nitrogen at -196 degrees Celsius.

In our previous article, My Stallion is Not Settling His Mares…What Do I Do?, we discussed possible causes for the decline in a stallion’s fertility and areas of reproductive management one can investigate further to determine if the infertility can be suitably managed or resolved. One tool a stallion owner/manager can use to better understand the reproductive status of their stallion is to have a breeding soundness exam (BSE) performed. In this article, Dr. Ed Squires outlines the components of a routine BSE which include: physical exam, reproductive history, testes palpation and/or ultrasound, semen evaluation, cultures and an assessment of his sexual behavior. A BSE provides valuable information on how to manage the stud and gives an indication of the number of mares he could breed.

How a stallion owner/manager responds to and handles mare owner concerns regarding semen quality or fertility can make or break a relationship or reputation. This article aims to give stallion owners an overview of the factors involved and provide a systematic guide to troubleshooting a resolution if possible. In Part 1 of this article, published in last month’s newsletter, we discussed the stallion’s breeding history, the importance of a breeding soundness exam (BSE), and stallion management practices as well as semen quality and evaluation. This month in Part 2, we will review common problems identified after the semen evaluation, the relevance of the mare book and their reproductive status and discuss the topic as it relates to those stallions breeding with frozen semen.