We have carried out a study about goat semen cryopreservation through the year (including breeding and non-breeding season, I mean). We have 10 adult male goats from two different breeds and they are our semen donors. Every week we have been collecting semen with artificial vagina and at the moment we have completed 1 year and interesting experiences I have. I see again that individuality is very important factor affecting success of cryopreservation. In our study I observed that semen from four male goats in ten are suitable for cryopreservation. And semen from six goats are not suitable for cryopreservation. Can you write your experience about this issue?
I want to discuss semen cryopreservation in goats with this question topic.
Hi, I have no experience with goats, but with rams and alpacas, we also used to do stallion semen cryopreservation in the lab. This is quite a common effect in species...it is commonly referred to as the "Stallion effect" in horses and quite often referred to in papers. In alpacas I have a huge difference between males in their ability to cryopreserve their semen. A lot was dependent on the protein composition of the seminal plasma, and also that for some males the dilution factor needed optimization. For example, males with a lower sperm concentration did not require as great a dilution. So, where we had previously used a standard 10 x dilution, for some males I needed to reduce this to x6 or x5. It may be something that you could try.
Hi Claire,
Thank you for your answer and explanation in current issue. I have also had some experience on ram semen cryopreservation. However, we used pooled ram semen in our experiments. So we could not determine differences amoung males in semen cryoperservation. At the momment we (cryo)preserve the semen from individual bucks (I mean we separetly (cryo)preseve). Also we want to obtain 100 milyon spermatozoa per straw for laparoscopic artificial insemination (LAI). So we have to diluted the semen in different ratio for each buck. For instance, today I have recently carried out a new replication, the concentrations of ejaculates is between one billion to 4 billion and so my dilution rates are approximately 1:4, 1:7, 1:8 and 1:11. It is exact that dilution rates directly affect the success of cryopreservation. Neverthless, we can not chance the dilution rates if we have to use straw for Artificial Insemination. Or we have to modiffy our Artificial Insemination techniques.
I think an other problem is seminal plasma ingredients. Seminal plasma ratio and ingredience is different among different individuals in goat semen. Also there is detrimental enzyme, called egg yolk coagulation enzyme (EYCE) or phospholipase A, in goat semen. EYCE causes the coagulation when you dilute the semen with extender containing egg yolk or milk if it is high concentrations. I can see the coagulations after dilution of goat semen in some times. We dont know at the momment the concentration and changes of concentration of EYCE in our study but in future we will have tested the level of EYCE in seminal plasma. I hope then I can exactly talk about effects of EYCE on cryopreservation success in goat semen. There are alot of study and paper about this issue, I also worked about this problem, but I have not reached any conclusion at the momment.
My Master's project was cryopreservation of goat semen (in 1981). The most important thing to know is that the seminal plasma is extremely high in phospholipase A2. If the sperm are not washed rapidly, the sperm membranes are attacked and they become nonviable. With less exposure time, the membrane permeability increases and the sperm have poor cryosurvival. It is ideal if they are diluted immediately with warm buffer then taken to the lab for centrifugation within minutes. The phospholipase also attacks the phospholipids in egg yolk, releasing lysolecithin, which also attacks membranes. Egg yolk buffers provide the best cryosurvival (skim milk is okay, but not quite as good), but it is important to include a calcium chelating agent to inhibit the phospholipase A2. Citrate buffers are just the thing. If you have more questions, feel free to contact me. I also just uploaded a copy of my Master's thesis that has all of the recipes and a discussion about washing goat semen.
Dear Erma,
Thank you for your sharing,
I have been working on cryopreservation of goat semen since 2005. Also my PhD thesis about cryopreservation of Angora Goat semen. In my opinion, goat semen must be washed to remove seminal plasma because of ingredient of egg yolk coagulating enzyme called Phospholipase A2. However, at the moment I am carrying out cryopreservation on Abasia and Georgian Goats semen. It is interesting we have not used any separation for seminal plasma and we carried out Laparoscopic AI. And it is exact that individual differences (I think) determine freezability and fertility capacity of cryopreserved semen. Also thermo-resistence of cryo-preserved semen is an important factor determining success of AI. For example, we obtained 60% progressive motility-PM (or higher, I know these results is incredible but we obtained good freezability) from two different individual bucks. They have similar PM but different thermo-resistence and so fertility capacity. I dont know what is the root of difference, I think we have to determine phospolipase A2 activity for each bucks and then we have to decide we exactly need separation of seminal plasma or not.
I have alot of questions in my mind about cryopreservation potential of goat semen. However I know that individual differences among bucks determine success of cryopreservation. We have to continue research and discussion about cryopreservation of goat semen.
My best wishes,
Umut
There are always differences between males in their natural fertility and in the resistance of their sperm to cryodamage (as mentioned by Claire Young). It is believed to relate to membrane lipid concentration, which can vary between males. Another important consideration is the oxidative stress of the semen. Oxidative stress (high levels of ROS) can impair cryosurvival. One thing you might consider is developing customized cryopreservation protocols for each buck. This has been used with some success for human sperm donors. In particular, if you are not using a citrate diluent, I would consider doing so. Good luck!
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