One of the frequent questions folks ask in Facebook chicken groups is “How long is sperm viable after a hen has been mated?” Invariably they want to know because their rooster has died or been rehomed, or sadly killed by a predator, and they would like to hatch some of his offspring. They get various responses, sometimes based on experience from others of doing just that, but I was curious about exactly how long hens could store sperm so I decided to do a little reading.
I was already aware that hens have ‘sperm storage tubules’, a fancy term for ‘pouches’ or ‘nests’ in their reproductive tract where they could save previously deposited sperm for a rainy day. Kind of like a withdrawal of a bank deposit when you want to have babies.
So How Do Sperm Storage Tubules Work?
Female birds and reptiles have evolved the ability to store sperm for varying periods of time to increase their chances of producing fertilized eggs and viable offspring. Chickens have 2000-3000 cylindrical tubes hidden in the folds of their vaginal tissues at two sites: either located in the lower portion of the infundibulum or the more commonly used ones found in the upper portion of the vagina at the utero-vaginal junction (UVJ).
The number of SSTs a hen is inherited through her genetics. If you are interested in breeding for increased fertility then select hens for their capacity to produce high numbers of hatched chicks, which corresponds, in part, with their high numbers of SSTs.
” The position of the utero-vaginal junction is indicated by an arrow. The approximate time of zygote residency within each part of the oviduct is also indicated.” – Journal of Reproduction and Development
Have you ever pondered the miracle of your existence? That of all the billions of sperm and millions of eggs two managed to beat the odds, get together in fertilization and produce a baby nine months later. Sexual reproduction is a marvel when you consider all the obstacles that can hinder successful fertilization.
Roosters have to transfer their sperm to the hen’s cloaca in a precarious dance coyly referred to as a cloacal kiss. (If you are unsure about the logistics of chicken reproduction read this post.)
Once sperm are deposited in the hen’s cloaca they race through a series of barriers that act as quality control check-points to weed out substandard sperm (i.e. low quality or damaged ones). The first barrier rejects dead and immobile sperm and poor ‘swimmers’. Very few sperm get past the next hurdle and on to the SSTs.
Hens have droplets from five types of fatty acids (lipids) in their reproductive tract. If high amounts of fatty acids are released into the SSTs they may cause irreversible damage to sperm, resulting in impaired sperm storage ability and decreased fertility.
Some hens carry a gene responsible for breaking down those fatty acids, which get released into the sperm storage tubules and improve the sperm’s survival. High concentrations of two types of lipid, oleic acid and linoleic acid, can increase the number of sperm still alive after 24 hours.
Any remaining rejected sperm are covered in vagina secretions and ejected out of the vagina.
There are a number of studies on SSTs, none of which had happy endings for the hens involved. As you can imagine, studying the adventures of sperm in the reproductive tracts of hens involves artificial insemination and then euthanizing and dissecting them to study where those sperm ended up.
As small flock keepers we can ascertain some of the same results by observation and keeping track of which of our hens’ eggs have high or low hatching rates. I always like to crack open unhatched eggs to see if they were fertilized or not, and if they developed, but died prior to hatch then when and why.
Here are some highlights of my reading:
- Storing sperm in the hen’s reproductive tract until the eggs are ready maximizes fertilization.
- Hens with more SSTs can store sperm for longer than hens with fewer SSTs.
- More storage pouches mean a greater ability to store more sperm.
- Successful long-term storage of sperm requires ideal conditions in the reproductive tract.
- Stored sperm can fertilize multiple eggs over time, meaning hens don’t need to mate again to fertilize additional eggs.
- Hens able to break down fatty acid secretions in the reproductive tract have higher fertility rates.
- Researchers are studying how the sperm and ova use fatty acids and suggest that supplementing hens’ diet with olives or sunflower seeds, foods high in oleic acid, could enhance fertility.
- Hens can store sperm from multiple males.
- Dominant roosters mate with hens first, subordinate roosters later. Hens have the ability to eject sperm from less desirable (i.e. subordinate) males.
And now the answer you’ve all been waiting for: hens can store viable sperm for @ 21 days.
Credits: Journal of Animal Science & Biotechnology; NCBI; Phys Org; Science Direct Featured Photo: University of Chicago Medicine