It has been reported that the source of egg yolk in Tris-based extenders affects semen motility in chilled dromedary camel ejaculates, and on post-thawing sperm motility and fertility in buffalo. For example, α-lactoglobulin has been shown to be deleterious to the survival of equine sperm. However, milk and egg yolk are biological fluids, and may contain components that are unfavorable for stallion semen.

Most commercial extenders require the addition of fresh egg yolk. The phospholipid, cholesterol, and the low-density lipoprotein content of chicken egg yolk have been identified as the protective components. The role of egg yolk in the cryopreservation of sperm is to be a resistance factor, which helps to protect against cold shock, and a storage factor, which helps to maintain viability. Chicken yolk is also one of the main components of the medium. Lipoproteins in skim milk protect spermatozoa from cold shock.

Skim milk-based extenders are effective in freezing stallion semen. Extenders usually are composed of sugars, electrolytes, egg yolk, and skim milk. Semen extenders affect semen quality, especially after freezing. The search for the optimal extender, combination of extenders, and the freezing protocol is relevant. Sperm freezing in horses is very important for the preservation of valuable, rare, and endangered genotypes. One of the reasons is the selection of stallions based on the exterior sports quality, and productivity, and not focused on reproductive qualities. The fertilizing ability of stallion sperm after freezing is lower than in other species. However, breeders prefer to use fresh or chilled semen. Artificial insemination of horses is widespread. In modern assisted reproductive technology programs such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), cryopreserved sperm are mainly used. Frozen semen preserves the horse’s genetics for a long time, even after death, allowing the material to be transported over long distances, around the world. Frozen semen has a number of advantages over fresh or chilled semen. In conclusion, Steridyl was proven to be a good diluent for freezing stallion semen, even though it was developed for ruminants.Īrtificial insemination is one of the main methods of genetically improving the horse population, due to the accelerated use of the best stallions.

No differences among extenders were seen in pregnancy rate. Six out of ten (60%) mares were pregnant after artificial insemination (AI) by LCCY frozen semen, and 9/12 (75%) by Steridyl frozen semen. No differences among the extenders were seen with the DNA integrity of spermatozoa. Semen frozen in Steridyl showed good stimulation of respiration by 2.4-DNP, which indicates that oxidative phosphorylation was retained after freezing–thawing. The number of spermatozoa with normal morphology in samples frozen in LCCY was 60.4 ± 1.72%, and with Steridyl, 72.4 ± 2.10% ( p < 0.01). The total and progressive motility of sperm frozen in Steridyl was significantly higher than in semen frozen in LCCY. Semen was collected from nine stallions, aged from 7 to 12 years old. Steridyl is a concentrated extender medium for freezing ruminant semen. The aim of this study was to compare lactose-chelate-citrate-yolk (LCCY) extender, usually used in Russia, and Steridyl ® (Minitube) for freezing sperm of stallions.

Minitube boar semen freezing