❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖ ❖
High-Fertility Proteins Enhance
Reproduction Rates in Dairy Cattle
Gary Killian, The Pennsylvania State University
Research, Education, and
fficient reproduction is criti-
cally important to the finan-
cial success of the dairy
cattle industry. Heifer calves produced
each year serve as future replacements for
older milking cows that have been retired.
To maximize milk production, cows
must become pregnant and give birth to
calves as often as possible. Delays in
entering a lactation cycle due to repro-
ductive failure result in lost income from
reduced milk sales.
More than 70% of the dairy cows in
the United States are bred by artificial
insemination, using genetically superior
sires. On average, only about 50% of
these matings result in calf births.
Numerous factors can affect the suc-
cess of cattle reproduction. Researchers
at The Pennsylvania State University are
studying how specific proteins in the male
and female reproductive tracts influence
the fertility of sperm from dairy bulls.
These scientists are studying extensive
data to document the fertility of individual
dairy bulls used for artificial
insemination. Their work is funded in
part by USDA’s National Research Initiative
(NRI) Competitive Grants Program.
Assessing the fertility of dairy bulls is
done by using their semen to inseminate
thousands of females, a task made possi-
ble only through artificial insemination
and good record keeping. Because the
fertility of individual bulls is known, com-
parisons are possible between the protein
composition of the seminal fluid (in
which sperm are suspended) from bulls
with high and low fertility.
Penn State researchers discovered that
seminal fluid from bulls with high fertility
typically contains two proteins in greater
amounts than seminal fluid from bulls
with low fertility.
Identifying the proteins in seminal fluid
associated with f