How Do Other Lubricants Harm Sperm?

Lubricating gels are part of daily life in any horse breeding facility. In particular, lubricants are used during semen collection and artificial insemination, where they can mix with sperm and decrease their normal function.

Specifically, Wright (2007) found that exposure of sperm to hyperosmotic lubricants and gels, such as Aquasonic Ultrasound Gel, KY, or Priority Care decreased fertilization potential of bull sperm by 60-100%.

Meyers (2007), has also reported that hyperosmotic conditions cause cytoskeleton reorganization in sperm, leading to sublethal motility and morphology defects associated with this damaged fertilization potential.

Other lubricants cause damage to sperm on contact through non-physiologic formulations, including abnormal:

pH The window for optimal stallion sperm function is narrower than for other species, being between 7.1 and 7.8, with a rapid decline in motility seen for pH levels above 8.0. Most lubricants have pH values below this optimal level. Sperm motility losses occur with acidic pH exposure. Conversely, pH levels above 8.0 can cause sperm to undergo acrosome losses and death.

In order to protect sperm from pH changes, lubricant pH must be stable during contact with air during handling. This requires a buffer, such as the phosphate buffers used in Pre~Seed EQ. Products that utilize sodium bicarbonate as a buffer (e.g. MiniLube) may cause sperm damage through pH increases to alkaline levels (outside of a CO2 incubator). This may be why sperm motility declines were reported with 10% concentrations of this product.

Osmolarity Sperm are also sensitive to both high and low osmolarity which causes them to either shrink or swell beyond their "critical volume limits". A physiologic osmolarity around 320 mOsm/kg (that of semen) is best for sperm function. Stallion sperm motility decreases linearly with exposure to increasing osmolarity above 400 mOsmo, such that sperm motion is basically abolished at 600 mOsm or greater.

Table 1 shows the very unphysiologic osmolality of several veterinary lubricants. The use of Priority Care® gel as a lubricant in an artificial vagina, for example, can cause equine sperm in the ejaculate to be rapidly and suddenly exposed to osmolalities as high as 800 mOsm. Both human and animal model studies suggest that these levels of osmotic shock are sufficient to cause irreversible damage to sperm, even after the sperm are moved into an isotonic situation.

Ionic Concentration Some veterinary lubricants (EquiLube & Priority Care) are formulated with glycols (such as propylene glycol) which permeate across sperm membranes into the sperm cell, and impact cell function. Although most lubricants with propylene glycol are hyperosmotic, EquiLube’s osmolarity is close to physiologic. However, sperm motility still declined during contact with Equilube in both fresh and cooled sperm storage (Samper, 2007). Likely this was due to the osmotic pressure coming primarily from propylene glycol molecules, rather than the ionic balance of salts in Pre~Seed EQ.

Table 1. pH & Osmolalities Levels for Veterinary Lubricants

*Osmotic pressure from Propylene Glycol, no salts
**Buffered by sodium bicarbonate only

Some people have suggested that mineral oil is appropriate for lubricating devices in the breeding shed; however, the pH and osmolality are not physiologic, and studies have shown decreased ability of sperm to penetrate ova in laboratory studies after mineral oil exposure.

Your breeding program, deserves a lubricant based on science and supported by clinical studies…

Pre~Seed EQ is the Right Solution for your breeding shed!