– Strategy to improve the fertility of frozen bovine semen by a facile technology that enables mass production of frozen straws containing selected healthy sperm and validation by artificial insemination showing high fertility results –
Researchers: YAMASHITA Kenichi, Leader, NAGATA MariaPortia, former Researcher, Biochemical Process Group, Advanced Manufacturing Research Institute
- Optimization of technology for selecting spermatozoa advantageous for conception via artificial insemination of cattle, and establishment of a mass production system using a simple device
- Confirmation that selected spermatozoa provided by a frozen straw packaging unit achieve a high conception rate without a change in breeding work
- Expected to contribute to improvement of livestock productivity through breeding improvement
Frozen semen straw produced using the newly developed technology (left), movement of post-thawed spermatozoa (upper right), and movement of spermatozoa of the same species of bull prepared using conventional technology (lower right)
Frozen spermatozoa prepared using the newly developed technology exhibit homogeneous movement and many swim in a meandering (zigzag) manner, which tends to facilitate conception.
In Japan, cattle breeding for livestock is generally performed by artificial insemination, but the rate of conception by this method has decreased in recent years. Various test studies are being conducted to improve conception rates from a wide range of angles including management of the physical condition and breeding of cows. However, with regards to improvement of semen and spermatozoa which attributes to bull or male factor, cryopreservation methods have not changed much since their establishment in the 1960s.
Frozen-thawed semen is used in cattle and other livestock breeding, but this generally involves a mixture of spermatozoa with different motility and lifespans, and dead spermatozoa are also not removed. To achieve further widespread use, it is important to improve the quality of semen and spermatozoa and to provide it in the frozen state sealed in the same type of straw as before so that the breeding work in the field remains unchanged.
The researchers jointly developed semen pretreatment technology for improving the conception rate by artificial insemination for cattle breeding in collaboration with Saga Prefectural Livestock Experiment Station, Morinaga Rakunou Co., Ltd., National Livestock Breeding Center, and Saga University. In addition, semen was mass produced and cryopreserved in a sealed state inside a straw packaging unit that is the standard distribution format, and a high conception rate was confirmed by field validation testing performed by using artificial insemination technique in cattle.
The researchers previously reported that spermatozoa advantageous for conception in each application such as artificial insemination or in vitro insemination can be identified based on the swimming pattern. This new research focused on artificial insemination of cattle with an emphasis on the simplicity of the production process, and developed mass production technology by scaling up the microchannels fabricated in the previous research. Furthermore, introduction to breeding sites is facilitated by securing an amount of semen that can be provided in the same frozen straw state as that used by existing breeding methods.