I have always been fascinated by the exquisite design of biological systems. The more we humans understand about biology, the more we realize we don’t know. The process of mammalian fertilization is one of these complex biological systems that in nature requires the proper coordination of so many factors ranging from the behavior of male and female to biochemical changes at the cellular and molecular level. Defined as: “A process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote”, fertilization requires that functionally viable sperm, at the right stage of maturity, are present in the oviduct of the mare during a brief window of time when a functionally viable oocyte is present.
Welcome to The Select Breeders Blog
The Major Causes of Damage to Sperm During Freezing…water and salts and ice, oh my!
Equine Seminal Plasma: The Good, The Bad and The Ugly
To understand why seminal plasma is beneficial in some situations and potentially harmful in others we must first review what it is, where it comes from and what we think are its roles in reproduction. The term seminal plasma refers to the fluid portion of ejaculated semen in which the spermatozoa are suspended. This fluid consists of secretions from the accessory sex glands in the stallion’s reproductive tract. These include the ampullae, the vesicular glands (seminal vesicles), the prostate gland and the bulbourethral glands (figure 1).
Collecting a Fractionated Stallion Ejaculate
There are many reasons and techniques for collecting a fractionated ejaculate from a stallion. In this article we will discuss some reasons why and demonstrate the technique we have used in our laboratory to manage a stallion with excessive gel fraction that contaminates ejaculates collected using standard in-line filter equipment.
Should Frozen-Thawed Semen Be Diluted Prior to Insemination?
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.
Quality Control is at the Core of the SBS Difference
The SBS network of affiliates is the acknowledged leader in the field of cryopreservation of equine semen. Each year we freeze thousands of ejaculates equating to tens of thousands of doses. In fact, this year the SBS Network will surpass the 50,000 ejaculate milestone since the company’s founding in 1987. When SBS was founded the company leadership made a commitment to quality of the finished product above all else. We wanted to put technology to use to help grow the equine frozen semen AI industry in the most responsible manner possible. It was clear early on that one of the major factors limiting the application of frozen semen in the horse industry was inconsistent quality of the product being put on the market. Breeders and veterinarians experienced frustration with attempts to use expensive semen that in many cases was of very poor quality. We knew that in order for breeders to realize the full potential of frozen semen technology they would have to be convinced that by applying strict standards for quality, frozen semen could be produced to achieve results similar to cooled semen. We also knew that these results would have to be produced in an efficient and economical way. Quality became the cornerstone upon which we would build our business.
Heat Stress and Equine Reproduction
During those dog days of late summer and the end of the breeding season, most of us who work in equine reproduction are ready for a break. You are left with those difficult mares that didn’t settle earlier in the season and stallions that may be growing tired of breeding. Mares may not cycle as predictably or conceive as readily and stallions may be tougher to collect or exhibit a decrease in semen quality. One of the factors that can contribute to these problems is heat stress. As ambient temperatures rise, stallions and mares may experience disruptions to normal reproductive function as a result. This article will briefly describe some of the effects of heat stress on mare and stallion reproductive function.
Splitting Doses of Frozen Semen
“I just purchased one very expensive dose of frozen semen from this incredible stallion. Is it OK to split the dose and breed two mares to try and get two foals?” or “The stallion owner only provides one dose per heat cycle and my vet would like to use a timed insemination protocol. Is it OK to split the dose and inseminate twice on the heat cycle?” At SBS we have heard these questions or some variation of them many times over the years. The answers are not simple ones. This blog article will follow up on two previous blogs that are also important in understanding the issue. See the recent blogs What Exactly is a Dose of Frozen Semen? and What is Progressive Motility?
What Is Progressive Motility?
The most commonly used measure of semen quality is sperm motility, specifically “progressive motility”. But what exactly does that mean and how is it determined? The minimum post-thaw “progressive motility” generally recommended for commercial distribution of frozen semen is 30% to 35%. This article will address some of the factors that can affect the assessment of sperm motility as well as the various problems associated with techniques used for determining “progressive motility”.
Processing Equine Semen for Cooled Transport
The advent of transported cooled semen significantly altered the logistics of the equine breeding industry. Shipping semen to mares rather than mares to stallions is incredibly more convenient; however it has resulted in the need for increased proficiency in semen processing techniques on the part of the stallion manager and expertise in reproductive technology and artificial insemination on the part of the field practitioner managing the mare. From the perspective of the stallion manager there are a number of factors that can influence the success of cooled transported semen such as stallion collection management, semen handling, extender composition, dilution rate, cooling rate, calculation of insemination dose and transport device. Our blog article this month will address the basic techniques for proper collection, evaluation and processing of stallion semen for cooled transport.
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.