Nanotechnology-Enabled Improvement of Reproductive Performance in Livestock Animals
Peter Sutovsky, PhD, Dr.h.c.
Division of Animal Sciences, and Department of Obstetrics, Gynecology and Women’s Health, University
of Missouri, Columbia, MO 65211, USA
Correspondence: SutovskyP@missouri.edu
Efficient herd reproduction by artificial insemination is of paramount importance to world agriculture.
Annually, cattle industry generates billions of dollars in farm income and the US commercial bull studs
alone sell close to two billion dollar worth of insemination doses. However, a substantial room for the
improvement of cattle reproduction is still possible through better assessment and management of sire
fertility. Despite progress in artificial insemination (AI) technology and timing, conception rates remain
suboptimal and sires of high genetic value are underutilized due to concerns about reduced conception
rates caused be poor semen quality and semen over-dilution.
In recent years, my laboratory developed a number of new techniques to improve fertility evaluation in
livestock animals and infertility diagnostics in humans. Among them, our technique for nanopurification
of semen used for cattle artificial insemination has been optimized and field tested, in collaboration with
colleagues at the USDA Livestock and Range Research Laboratory in Fort Keogh, Montana, and Select
Sires Cooperative, Plain City, Ohio. A semen batch collected for insemination contains normal sperm
cells able to fertilize an oocyte, as well as a portion of defective sperm cells that lack the fertilizing
ability. These abnormal spermatozoa can be in some, but not all cases identified by light microscopic
semen analysis; they dilute the content of fertile, normal spermatozoa in a semen dose and may even
release decay products, reactive oxygen species (ROS) that hinder or even damage fertile spermatozoa.
To improve conception rates after AI, we developed a nanotechnology to remove such defective
spermatozoa from bull semen. This technology is aimed at improving the pregnancy and calving rates
and reduces the number of sperm cells in a single AI semen dose, needed to achieve cow pregnancy.
Consequently, more insemination doses of high fertility can be generated from sires with high genetic
value.
The principle of semen nanopurification is based on the presence of unique cellular determinants, such
as proteins and glycans coating the surface of defective or damaged sperm cells, but entirely absent
from the surface of fertile spermatozoa. We coated iron oxide nanoparticles with antibodies and lectin
molecules with high affinity to two such defective sperm surface determinants, sperm protein ubiquitin
and a group of glycans inside the sperm head acrosome, recognized preferentially by the plan lectin PNA
(peanut agglutinin/Arachis hypogea lectin). Upon mixing with semen, the particles bind to defective cells
and can therefore be pulled down with a strong magnet. This magnet holds the nanoparticle coated
defective spermatozoa on the bottom of test tube, while the fertile, viable spermatozoa are removed
with supernatant and processed for storage in liquid nitrogen. This protocol is easily incorporated in the
routine workflow of semen processing at a bull stud. After semen collection and pre-processing, the
particles are mixed with spermatozoa in a test tube and allowed to incubate for 15 minutes while gently
mixed. Next tubes with semen are set on top of a strong magnet and the fertile spermatozoa are
removed and processed for final dosage in semen straws. In laboratory tests, the nanopurified semen
demonstrated increased viability by flow cytometry and superior fertilizing capability by in vitro
fertilization (IVF).
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To validate semen nanopurification as a tool for commercial agriculture, we conducted two controlled
field AI trials in two consecutive years, in which we inseminated 798 beef cows with raw or nanopurifed
semen from six sires. We reached an average conception rate of 65% with a half-dose of nanopurified
semen. This conception rate was comparable to that of a full dose of control non-purified semen from
the same sires and collections, and significantly higher than a half dose of control semen. Importantly,
we have not observed any negative side effects on the inseminated animals.
In conclusion, semen purification technology allows maximizing the utilization of sires with high genetic
value without a substantial added cost. Since the method is inexpensive and fully integrated into current
protocol for semen cryopreservation, it is feasible for the use in the cattle industry.
Acknowledgements
This work was supported by grants from US Department of Agriculture, the Missouri Life Science Trust
Fund and The Food for The 21st Century Program of The University of Missouri, as well as by in-kind
contributions from Select Sires Incorporated and USDA Agricultural Research Service.
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