The CSU Equine Reproduction Laboratory is your ultimate resource in equine reproduction.
03/12/2025
Dr. Patrick McCue breaks down s***m motility vs s***m fertility 🔬🐎
👉Sperm motility refers to the percentage of s***matozoa that exhibit movement when viewed under a microscope. Motility is often subdivided into either total s***m motility or progressive motility. Total s***m motility refers to the percentage of s***m in a sample that exhibit any type of movement, including forward movement, circling, twitching, etc. Progressive s***m motility refers to the percentage of s***m in a sample that exhibit forward movement. It is commonly assumed that s***matozoa exhibiting progressive motility are the ones that will progress up the female (i.e. mare) reproductive tract and reach the site where they may fertilize the oocyte (egg) after ovulation. There is a general correlation between s***m motility parameters and fertility, as determined by pregnancy rates, but there are many other factors that affect pregnancy rates in mares.
👉Fertility refers to the ability of a male (i.e. stallion) to generate pregnancies in females. Fertility is often categorized as either seasonal pregnancy rate or per-cycle pregnancy rate. Seasonal pregnancy rate is defined as the percentage of mares that become pregnant during any cycle during a given breeding season. The per-cycle pregnancy rate refers to the percentage of mares that become pregnant during an individual estrous cycle. Common fertility parameters monitored for stallions include first cycle pregnancy rate (percentage of mares that become pregnant after being bred on their first estrous cycle) and seasonal pregnancy rate. Other parameters may include number of estrous cycles per pregnancy and live foal rate. The terms conception rate and pregnancy rate are often used inappropriately. Technically, conception rate refers to the percentage of mares in which conception or fertilization of the oocyte occurred. Fertilization of the oocyte may occur in a high percentage of mares that are bred, but early embryonic loss may significantly reduce the number of mares that are determined to be pregnant during an ultrasound examination at 14 days after ovulation.
