Research Suggests Batch-Thawing
Semen Does Not Compromise Fertility
INDIANAPOLIS, Ind., July 28, 2001 — Research presented today at the joint
meeting of the American Dairy Science Association and American Society of
Animal Science in Indianapolis suggests that inseminators who follow
recommended semen-handling procedures can batch-thaw more than two units of
frozen semen without compromising conception rates. These findings are
particularly important for technicians inseminating a large group of cattle
at one time, enabling increased labor efficiency while maintaining breeding
effectiveness.
"This study’s results contrast with those of two previous reports on this
topic from smaller data sets obtained in Hawaii and Colorado, each of which
concluded that thawing more than two straws at once results in reduced
conception rates of the third or greater straw used in sequence," says Mel
DeJarnette, reproduction specialist, Select Sires, who monitored the
research project. "Although we seldom recommend thawing more than about four
or five straws of semen at a time, our data suggests that proficient
inseminators who follow recommended semen-handling procedures could thaw
seven or more straws at once with no reduction in fertility."
The data for this study were obtained by a professional A.I. technician
breeding cows in 27 herds in western New York from June 1999 through May
2000. When multiple straws were thawed at once, the technician recorded the
breeding date and sequential insemination number (SIN), as well as
identification information for each herd, cow and service sire. Pregnancy
information was obtained by cross-referencing collected data with on-farm
databases after routine pregnancy checks.
The analysis of pregnancy data on 6,122 inseminations showed that SIN had no
effect (P=0.50) on conception rate, and that batch-thawing semen straws did
not cause a decline in semen fertility. By SIN group, the conception rates
ranged from 29 percent (the sixth animal inseminated) to 35 percent (SINs
greater than or equal to seven). The number of inseminations per SIN group
were high enough to ensure a high probability of detecting fertility
differences if they existed, with
numbers ranging from 406 (seventh or greater unit of semen deposited in a
cow in sequence) to 1,260 (first unit of semen used in sequence).
"By collecting data on more than 6,000 cows in 27 herds for 12 months, we
were able to evaluate variations in fertility due to SIN, herd, season,
sire, whether the insemination was a first service or repeat service, as
well as the interactions among these effects," says DeJarnette. "It was
interesting to note that the season-by-SIN interaction was not significant,
suggesting that the time of year did not affect the success of
batch-thawing."
Despite the positive results of this research, it’s important to remember
that – as suggested by both prior studies – if not properly managed, thawing
too many straws at once can have negative effects on semen viability and
fertility. Proficient inseminators breeding cows in an ideal environment
(where cows and the semen-thawing area are logically arranged and in close
proximity) can batch-thaw and deposit straws in less than one minute per
cow. However, when inseminators lack proficiency or where the cows and
thawing area are not in close proximity, the insemination time can exceed
five minutes per cow.
"Arbitrarily setting a maximum number for batch-thawing unjustifiably
handicaps the efficiency of the proficient inseminator and lends a false
sense of security to the less-than-proficient inseminator," says DeJarnette.
"To maintain maximum fertility, the inseminator should focus on the real
issues of time and temperature, regardless of the number of straws being
thawed."
Most A.I. organizations and the National Association of Animal Breeders
(NAAB) recommend that technicians thaw semen straws in 92- to 98-degree
Fahrenheit water, and maintain the straws at that temperature until
deposited in the cow — which must occur within 10 to 15 minutes of thawing.
In addition, DeJarnette warns inseminators who wish to practice
batch-thawing that straws must not be allowed to contact each other in the
thaw bath. A Washington State University study clearly demonstrated that
straw contact during the thawing process results in a reduced thaw rate and
compromised sperm viability.
Based in Plain City, Ohio, Select Sires Inc. is a federation of 10
farmer-owned and controlled cooperatives. It provides highly fertile semen
as well as excellence in service and programs to achieve its basic objective
of supplying livestock breeders with America’s best genetics at a reasonable
price.
Copyright 1996-2001 Select Sires Inc. Last updated 28-Jul-2001.
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