Transporting pig semen doses from boar stud to breeding farm is much more than just simple delivery. Temperature differences as well as vibrations are just two factors that can affect semen quality during the journey. Let’s follow semen dosages as they travel from the AI centre to the farm. What can happen and what needs to be looked out for?
Before the onset of this imaginary journey, it is good to introduce a few vital aspects of semen transport. The most important of them is temperature. The optimum temperature range for preservation of semen doses is 15–19ºC. Under those conditions, the semen’s lifespan is maximal and the sperm cell’s viability is preserved for a longer period, because its metabolic activity is decreased at basal levels without altering the integrity of its membrane and various organelles. So before anything else, it’s essential to keep the temperature constant throughout transport as well as in the farm’s storage unit, avoiding temperature fluctuations as much as possible (see Figure 1).
Another aspect to keep in mind is thermal inertia. This means that liquids like semen doses are often unlikely to rapidly change temperature. In practice, this means that when the transport begins in hot conditions, storage units for conservation will be unable to sufficiently cool the doses. Thermal inertia can, however, also be an advantage when doses have reached the desired temperature prior to being transported – irrespective of whether the semen is delivered under controlled conditions or by courier.
Thirdly, during transport, semen doses are going to be submitted to stress factors, including potential temperature variations as well as physical vibrations. That can result in errors (see also Figure 2).
Finally, transportation involves three parties – a boar stud, a farm and an (external) transporter. All have different roles to play and different interests in the process. Maintaining a good balance between the three is important (see Figure 3).
There are several things to keep in mind when starting a semen transport. The following set of recommendations is aimed at achieving dose transport under controlled temperatures.
Sometimes, however, transport under controlled temperature may not be possible. When there is no other option but to send semen doses without controlled temperature management – that is, using courier companies – then proper insulation of the parcel is recommended to prevent variation and fluctuation. Here is what to do:
A factor that has been recently studied is the possible effect of vibrations that occur during transport. As semen doses are produced in large AI centres and the routes can involve long distances and take a long time, depending on their geographical location or the country, vibration can be an important factor.
In recent years, several authors have described vibration potentially having an impact because it increases the medium’s pH and oxidative stress levels. Therefore, it will affect mitochondrial activity, acrosome and plasma membrane integrity, as well as motility.
Arrival is a very important moment, as this is when temperature maintenance meets biosecurity. It is highly advisable to construct a cabin or small room with a storage unit for preservation where semen doses can be left at any time, without people entering the farm. If that not possible, an alert system could be installed for the farm staff to step out and collect the parcel. Some scientific authors state that at least 90% of deliveries must be put in the storage unit in under 15 minutes.
Nowadays there are companies with traceability systems that let producers know where their semen doses are, what the storage temperature and expected delivery time at the farm are, etc. The aim is to have constant transparency to customers on the product’s condition.
The last step includes proper storage inside the farm. Several recommendations are important at this stage as well:
Last but not least: rotation. A controversial topic has been that of the rotation of the semen doses. It is a practice routinely carried out on farms with the aim of preventing sperm sedimentation, in a medium considered ‘toxic’ due to the accumulation of metabolic waste of the sperm cell.
To date, there have been several publications dealing with the effect of rotation on the quality of semen doses. Although in the past* it was believed to be beneficial, more recent research** has found evidence of the negative effect that this practice can have on semen quality. It is also believed that it can favour the loss of CO2 from the liquid phase to the air in the semen doses, leading to accelerated alkalinisation of the medium. This occurs with greater intensity with the use of short-term extenders, since buffers in their composition are simpler than in high-performance extenders.
All factors addressed above must be taken into account, since these days networks can be large and complex, subject to completely different scenarios depending on multiple factors. Therefore, each company should adapt to the surrounding context and adopt the necessary strategies to obtain the desired quality standards for its final product, the semen dose.
* Research by Rodríguez-Gil and Rigau 1995.
** Schulze 2015, Bortolozzo 2017.
References available on request