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College of Agricultural Sciences · Cooperative Extension
Reproductive
management systems
for artificial insemination
of dairy heifers
Michael L. O'Connor
Department of Dairy and Animal Science
The Pennsylvania State University
324 Henning Building
University Park, PA 16802
(814) 865-5491 · FAX (814) 865-7442
www.das.psu.edu/teamdairy/
______________________________________________________________________________________________________________________________________________________________________________________________________________________
Topics Include:
Advantage of artificial insemination (AI)
Use of heifer AI
Physiology related to synchronization programs
Systems for managing an AI program for heifers
Inseminating a group of synchronized cattle
___________________________________________________________________________________________________
PENpages 2890220 DAS 93-44 IVE2d
ADVANTAGE OF ARTIFICIAL INSEMINATION
_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Artificial insemination (AI) of dairy heifers available, then dairy producers can sell heifers
provides numerous advantages to the dairy based on genetic criteria. In addition, heifers tend
producer. Foremost is the opportunity to improve to be the most fertile females in the herd (Table
the entire herd's genetic merit. USDA sire 2), thus they are more likely to conceive to AI.
summaries document that active AI bulls have a These advantages document the tremendous
significant advantage in transmitting ability for opportunity that exists with use of AI for heifers.
milk, fat , and protein dollars over non-AI bulls.
Related to the genetic merit from the sire The fact that the AI sires are examined and tested
component is the fact that heifers born of AI for reproductive soundness and disease, and that
matings are genetically the best animals in the semen quality and fertility are routinely
herd. These AI-sired heifers provide more quality monitored are additional benefits of using AI for
replacements and a greater opportunity to cull heifers. Based on the results of breeding
animals of lower genetic merit. The data in Table soundness examinations performed on sixty-six
1 illustrates that approximately 30 percent of on-farm dairy bulls by one veterinary clinic in
calves born each year are progeny of first-calve California, 26 percent of the bulls were
heifers. Therefore genetic merit should not be considered unsatisfactory. Breeding to a
wasted through the use of natural service. subfertile or infected natural service sire will
cause a significant delay in the interval to
Merchandising is another advantage for AI-sired conception.
heifers. If quality AI-sired replacements are
Table 1. Percent of calves born by lactation number
Lactation No. % Calves born
_________________________________________________________________________________________________________________________________________________________
First 31.9
Second 25.1
Third 18.6
Fourth 12.8
Fifth 7.1
Sixth + 4.5
_________________________________________________________________________________________________________________________________________________________
Raising Dairy Heifers, A Supplement to Hoard's Dairyman, 1990, Dairy Heifer Suppl.
Table 2. Effect of age/lactation number on conception rate
Lactation No. Conception Rate
_________________________________________________________________________________________________________________________________________________________
Heifers 59.3
1st 50.8
2nd 48.9
3rd 48.3
4th + 38.2
_________________________________________________________________________________________________________________________________________________________
Gwasdauskas, et al., 1981, J. Dairy Sci. 64:358
_________________________________________________________________________________________________________________________________________________________________
DAS 93-44 Reproductive management systems for artificial insemination of dairy heifers 1
ADVANTAGE OF AI (continued)
_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Sire summaries, which provide accurate to be recorded, and calving dates more accurately
production, type, and calving ease information, predicted. In a pasture-breeding situation, heifers
are available. By using AI sires, dairy producers with reproductive problems are not identified
can use semen from several sires to minimize the until considerable time is lost. These heifers
risk of obtaining progeny from one low genetic would probably not calve at the optimum age of
merit sire (whether from a natural service sire or 24 months, resulting in lost profits. Finally, the
an AI sire whose genetic evaluation declined as danger associated with maintaining a bull on the
more information became available). Also, farm should not be ignored.
breeding dates are more likely
USE OF HEIFER AI
_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
A 1992 survey indicated that 86 percent of Reproductive management systems have been
Pennsylvania dairy producers use AI for their used and are being refined to minimize time spent
lactating herds, but only 85 percent of these use for estrous detection and to manage an AI
AI for heifers. Thus, we can assume that over program for heifers that are located some
one fourth of all Pennsylvania dairy producers distance from the main dairy facility. Acceptable
fail to take advantage of this opportunity. This conception rates can be achieved with properly
group was asked whether they agreed, disagreed, designed and implemented programs. For a
or were uncertain about various statements relatively small investment in time and money,
related to using AI for heifers. The major reasons most heifer facilities can be upgraded and
they gave for not using it were the perception of equipped to provide restraint and efficient
lowered conception rates with AI, difficulty or handling facilities for heifers. In addition to
time involved with estrous detection, location of administering treatments for estrous
heifers was inconvenient, and lack of restraint synchronization and insemination, such facilities
facilities. (Table 3.) can also be used for vaccination, deworming,
pregnancy examinations, and perhaps even
embryo transfer.
Table 3. Percentage of producers who do not use AI for heifers and
who agree with the listed statements
Statement % Agree
_____________________________________________________________________________________________________________________________________
AI for heifers is not profitable. 10
Conception rates are lower with AI. 45
There are more calving problems with AI. 20
Heat detection takes too much time. 57
Estrus is difficult to detect. 33
Synchronization is not profitable. 20
Synchronization requires too much labor. 27
The location of the heifers is inconvenient. 79
Lack restraint facilities 80
_____________________________________________________________________________________________________________________________________
(Sulaiman, F., 1992, Penn State)
_________________________________________________________________________________________________________________________________________________________________
DAS 93-44 Reproductive management systems for artificial insemination of dairy heifers 2
PHYSIOLOGY RELATED TO SYNCHRONIZATION PROGRAMS
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Research during the last decade has provided degeneration of follicles during the cycle, the
new information about changes in growth and response rate and time to onset of estrus
degeneration of ovarian follicles during the following PG injection may well depend on the
estrous cycle. Using real-time ultrasound degree of synchrony of follicular development
technology to monitor ovarian structures on a and CL regression. Research shows a negative
daily basis, several independent research groups relationship between size of the preovulatory
recently showed that cattle might develop two, follicle present when the corpus luteum regressed
three, or four groups of follicles during each (progesterone fell below 1 ng/ml) and the interval
estrous cycle. Usually, one in each group from luteal regression to the preovulatory surge
becomes dominant, suppressing the growth of the of luteinizing hormone (LH). Luteinizing
other follicles within the group. Such groups of hormone causes ovulation. This interval was
developing follicles are called waves of follicular longer in heifers when a small follicle was
growth. Thus various populations of small, present, compared with heifers in which a large
medium, and large follicles are present on the developing follicle was present at the time of
ovary each day of the cycle. luteal regression.
In a study conducted at Penn State, 150 dairy
heifers were injected with PG on either day 7, 11,
Prostaglandin or 15 of their cycle. (Table 4.) The percentages
This concept of follicular development might of heifers that expressed heat by the fifth day
explain the variation seen in intervals from post-injection were 86, 90, and 98 for each
prostaglandin (PG) injection until the onset of respective group. However, there was wide
heat. Several studies have shown that--even variation in the average interval to onset of
though cattle have a corpus luteum (CL) and are estrus, the percentage of estral heifers exhibiting
likely to respond to PG--there is considerable estrus between 32 and 48 hours, and by 72 hours
variation among cows and heifers in the interval post-injection. Heifers were inseminated 12 hours
to onset of heat and degree of synchrony of heat, after standing heat was first observed. Pregnancy
depending on the age of the CL (day of cycle) rate to first service for the heifers that exhibited
when PG is administered. Since there are several estrus averaged 76 percent, and there was no
waves of growth and difference between groups.
Table 4. Variation in onset of estrus among dairy heifers treated
with prostaglandin at different stages of the estrous cycle
% estrous heifers exhibiting heat
______________________________________________________________________________
Day of Average hours % showing 32-48 hours by 72 hours
cycle to onset of estrus estrus post-injection post-injection
_______________________________________________________________________________________________________________________________________________________________________________________________________
Day 7 44 + 8.3 86 65 100
Day 11 72 + 14.3 90 4 49
Day 15 53 + 12.2 98 29 96
_______________________________________________________________________________________________________________________________________________________________________________________________________
Tanabe and Hann, 1984, J. Animal Sci. 58:805
_________________________________________________________________________________________________________________________________________________________________
DAS 93-44 Reproductive management systems for artificial insemination of dairy heifers 3
PHYSIOLOGY RELATED TO SYNCHRONIZATION PROGRAMS
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
If the heifers in the groups treated with Syncro-Mate-B (SMB) is the only progestogen
prostaglandin on days 7 and 15 were inseminated currently approved for use in dairy heifers. Two
at 80-hour appointment breeding, the conception other systems, melengestrol acetate (MGA),
rate would likely be low because insemination which is administered in the feed, and the
would have been too late in relation to the onset progesterone-releasing intravaginal device
of estrus. Heifers injected midcycle (day 11) (PRID) have been thoroughly researched (MGA
would probably have had an acceptable is currently being reviewed by the FDA). Syncro-
conception rate if they were appointment bred at Mate-B consists of an ear implant containing the
80 hours. Generally, fixed-time insemination progestogen, Norgestomet, and an injectable
following prostaglandin treatment is not as solution of Norgestomet and estradiol valerate.
successful as insemination based on standing The injection causes premature regression of the
heat. Although follicle size was not recorded CL in heifers that recently ovulated, and inhibits
during this project, the status (developing or the final stage of follicular development in other
degenerating) and size of the developing follicle heifers. The implant inhibits development of the
present at the time of PG injection may have new CL and simultaneously prevents follicular
determined the degree of synchrony and time to growth until its removal nine days later. Once the
onset of heat post-injection. implant is removed, a new cycle commences, and
heifers generally exhibit signs of heat beginning
Progestogen treatment at 38 to 48 hours later. The mechanism of action
Various synthetic progesterone products, or of the other progesterone products is similar to
progestogens, have been used for synchronization SMB. Compared to PG, progestogen treatment
of ovulation and estrus. has the advantage of inducing estrus in some
prepubertal heifers.
SYSTEMS FOR MANAGING AN AI PROGRAM FOR HEIFERS
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Visual observation for estrus and AI activity, and occasionally first services do not
occur in a timely fashion, delaying the age at first
According to a Pennsylvania survey (Heinrichs et calving.
al., 1987) of heifer management practices, 79
percent of the farmers used visual observation Prostaglandin estrous synchronization
for estrus to determine time of insemination. The programs
combination of visual observation and
Results of a 1992 Pennsylvania survey regarding
insemination based on standing to be mounted
reproductive management practices indicated that
can be an effective method of breeding heifers.
approximately ten percent of dairy producers use
However, the efficiency and accuracy of estrous
estrous synchronization for heifers. In addition,
detection varies greatly among farms. In some
44.7 percent occasionally use this practice.
situations, this becomes a labor intensive
(Table 5.)
_________________________________________________________________________________________________________________________________________________________________
DAS 93-44 Reproductive management systems for artificial insemination of dairy heifers 4
AI FOR HEIFERS (continued)
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Table 5. Percentage of Pennsylvania dairy producers
who use estrous synchronization for dairy heifers
Frequency Percent
_____________________________________________________________________________________________________________________________
Never 45.5
Occasionally 44.7
Most of the time 8.9
Consistently 0.9
_____________________________________________________________________________________________________________________________
Sulaiman, 1992, Penn State
Prostaglandin estrous synchronization of careful observation may be required to
programs (continued) observe all the heifers that responded to PGF.
This system requires frequent and conscientious
Several systems using prostaglandin have been heat detection.
developed, and researchers, veterinarians, and
producers have adapted programs to suit specific System 2. Cattle are inseminated by appointment
herd situations. In selecting a system, at a specified time after the second injection. The
consideration should be given to the following time will vary--it may be 72 or 80 hours post-
factors: injection--depending on the PG product used.
· amount of time that can be devoted to heat Research has consistently shown that conception
detection following PG injection and pregnancy rates are higher when cattle are
inseminated based upon standing heat versus
· degree of accuracy and efficiency of heat appointment breeding. Heifers that are in heat as
detection that can be expected early as 24 to 54 hours after the second injection
· frequency of handling heifers would not conceive with appointment
· price of semen to be used insemination, but would likely conceive if
inseminated twelve hours after the onset of
· desired pregnancy rate
estrus. Double-insemination at 72 and 96 hours
Results of synchronization can be expressed after the second injection has been shown to
several ways, including the number of animals result in conception rates approaching those
induced into heat during a specified period of achieved in System 1.
time (synchrony), conception, and pregnancy
System 3. This program is a variation of System
rate. Conception rate is the number of animals
1, in which all heifers detected in heat after the
that conceived, divided by the number that were
first PGF injection are inseminated, and only
inseminated. Pregnancy rate refers to the number
those animals not observed in heat are reinjected
that conceived, divided by the number that were
14 days later and inseminated based on observed
assigned to the synchronization program.
heat. The advantages are timely insemination and
System 1. All eligible heifers are injected twice the need for less prostaglandin compared to
with PG, 14 days apart, and those heifers that System 1. However, there are two three-day
express estrus after the second injection are periods of heat detection.
inseminated. Although a large percentage of them
A comparison of systems 1, 2 and 3 is
will come into heat between 48 and 72 hours
after the second injection, five to six days presented in Table 6.
_________________________________________________________________________________________________________________________________________________________________
DAS 93-44 Reproductive management systems for artificial insemination of dairy heifers 5
AI FOR HEIFERS (continued)
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Table 6. Comparison of prostaglandin synchronization programs for heifers
Program No. Heifers % Pregnant
_______________________________________________________________________________________________________________________________________________________________________________
AI at estrus after 1st PGF 766 65
AI at estrus after 2nd PGF 1025 61
AI at 80 hrs after 2nd PGF 945 39
_______________________________________________________________________________________________________________________________________________________________________________
Fogwell et al., 1986, J. Dairy Sci. 69:1665.
System 4. Another plan consists of inseminating this system provides a check on cycling status.
at the time of detected heat and by appointment. This plan generally requires only 40 percent as
Animals not inseminated following detected heat much PG as the two injection systems.
by 72 hours are inseminated by appointment. Approximately 80 percent to 90 percent of the
This approach combines the advantages of the cycling cattle are observed in heat during the
systems already discussed. Cattle are inseminated synchronization period. However, it does require
at the optimum time when inseminated at heat, eleven days of heat detection. With any system
and they achieve high conception rates. Breeding involving insemination at detected heat, heat
the remaining animals at a fixed time (72 or 80 detection aids are effective in helping to
hours) ensures that those animals which will determine which animals are in heat.
ovulate but not detected in heat still have a
chance to conceive. Good pregnancy rates can be System 6. This system is designed for
achieved. synchronization of large groups of heifers when
heat detection is not practical, but where self-
However, if the percentage of cattle detected in locking head gates or stanchions are available.
heat during the first 72 hours is low, then it is All heifers eligible to be bred are injected with
advisable to continue to inseminate based on PG, and two days later the tailheads are marked
detected heat and not to inseminate by with paint or chalk. On the morning of the third
appointment. This avoids wasting semen on day, heifers with the markings rubbed-off are
animals not cycling. inseminated. Any heifer that was observed in
standing heat that morning, but has markings that
System 5. This final plan uses a single PG were not completely rubbed-off, was also
injection with six days of heat detection before, inseminated. Proper heifer identification and
and five days after, the injection. Cattle are diligent record keeping are essential with this
checked for heat at least twice daily for six days method. Injections are administered in the neck
and inseminated 12 hours after observed heat. On region so that identification can be confirmed.
the sixth day, the remaining animals receive PG Figure 1 describes the program and results of a
and are inseminated as they come into heat over field trial conducted in a large herd in the state of
the next five days. Thus, the total program is Washington (Van de Graff et. al., 1993 JDS
eleven days in length. Suppl. 1). Approximately 2,000 heifers were
When working with a large group of cattle, and processed through the system, and 74 percent
heat detection is good, 15 percent of the herd were inseminated artificially, of which 62 percent
should be in heat during the first four days of this conceived. Thus, the overall pregnancy rate was
program. If less than 15 percent have shown 46 percent. The entire process can be repeated as
heat, this is an indication the number of cycling new heifers become eligible for breeding and for
animals is low. Attempting to synchronize this heifers that were not inseminated during the first
group will probably be unsuccessful. Therefore, cycle through the system.
_________________________________________________________________________________________________________________________________________________________________
DAS 93-44 Reproductive management systems for artificial insemination of dairy heifers 6
AI FOR HEIFERS (continued)
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Figure 1. System 6: Prostaglandin, tailhead marking, and insemination
CHECK CHALK REPEAT (2 weeks later)
PG CHALK AND AI FOR HEIFERS NOT BRED
__________________________________________________________________________________
TUES THUR FRI TUES THUR FRI
AM AM
Between 100 and 200 heifers were processed Labor efficient restraint facilities such as self-
through this program per week. Based on locking head gates are essential to the success of
progesterone analysis of several hundred heifers such a program.
on the day of insemination, there was only a 2.5
percent error rate in the heifers inseminated when
progesterone levels were elevated. Furthermore, Progestogen treatment regimes using Syncro-
it should be noted that 16 percent of those heifers mate-B
that were not inseminated had high estrogen and
low blood progesterone levels on the morning of Two basic systems for SMB are currently
the third day and, and thus would likely be in approved for heifers. System 1 involves
estrus that evening or the morning of the implanting the animals with Norgestomet and an
following day. Restraining the heifers and intramuscular injection of Norgestomet and
examining tailheads again that evening may have estradiol valerate. The mechanism of action of
resulted in more heifers being inseminated. The this treatment was described earlier. The
data confirmed the low error rate associated with implants are removed after nine days, and cattle
this PG-heat detection aid, programmed breeding are inseminated when they are observed in heat.
system. It can reduce the time spent for In System 2, the animals are inseminated by
reproductive management to only a few days appointment, 48 to 54 hours after implant
each month and can be used at a remote location removal. A modification of System 2 involves a
where heifers cannot be watched intensely for second insemination of those heifers which
estrous behavior. exhibit estrus after the 48- to 54 hour, timed
insemination. A comparison of these three
systems is presented in Table 7.
Table 7. Comparison of Syncro-Mate-B programs for dairy heifers
Program No. Heifers % Conception
_____________________________________________________________________________________________________________________________________________________________
Controls 119 74
AI at SMB estrus 119 66
AI at 48 hrs after SMB removal 119 58
AI at 48 hrs + AI at estrus after 48 hrs 122 61
_____________________________________________________________________________________________________________________________________________________________
Hansen,1985. Brigham Young University
_________________________________________________________________________________________________________________________________________________________________
DAS 93-44 Reproductive management systems for artificial insemination of dairy heifers 7
AI FOR HEIFERS (continued)
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Most studies comparing SMB with PG have recently been modified to include a PG injection
shown a tighter synchrony of estrus with SMB. If 24 hours before the PRID is removed. Generally,
timed (appointment) insemination is to be used, the synchronization of heat and ovulation, and
SMB is the product of choice. Progestogen the fertility have been good with this system.
treatment provides the additional advantage of Although considerable research has been
inducing estrus in some noncycling, pre-puberal conducted with this system, it has not been
heifers. One drawback to SMB is that farmers approved for use in the United States.
unfamiliar with implanting and implant-removal
techniques may find it difficult or inconvenient to Melegestrol acetate (MGA) + prostaglandin
use, resulting in poor response rate. (PG)
The cost for ten SMB units is about $85 with the Melengestrol acetate is an orally active
implanting device or $65 without the device. This progestogen that was developed in 1962. Early
is comparable to the price of two doses of PG. studies feeding MGA for short- or long-term
duration resulted either in poor synchrony of
Progesterone-releasing intravaginal device estrus or good estrous synchronization, but poor
fertility. More recently, an MGA + PG system
Another method of administering progesterone is was developed. Melengestrol acetate is fed at a
the progesterone-releasing intravaginal device rate of 0.5 mg/hd/day for a 14-day period. The
(PRID). This device is inserted into the vagina MGA is fed in a grain carrier and either top-
and gradually releases progesterone, which is dressed or blended-in with larger quantities of
absorbed by the vaginal tissue. The progesterone feed. Consistent intake of MGA is critical.
produces physiological effects similar to the Heifers will exhibit heat beginning within 48
progestogen in the SMB treatment described hours after withdrawal of MGA. However, since
above. After a specified number of days (usually fertility is low, they should not be inseminated at
seven), the device is removed, and the cattle are this time. The heifers are injected with PG 17
inseminated by appointment or when they exhibit days after MGA withdrawal and then
heat. This treatment has inseminated based on observed estrus. The
results of nine field trials in Kentucky are
summarized in Table 8.
Table 8. Results of MGA + PG estrous synchronization system for beef heifers
Location Estrous response Conception Pregnancy
# % # % # %
_________________________________________________________________________________________________________________________________________________________________________________________________________________
1 23/24 96 18/23 78 18/24 75
2 49/60 82 35/49 71 35/60 58
3 21/31 68 14/21 67 14/31 45
4 27/29 93 22/27 81 22/29 76
5 18/19 95 13/18 72 13/19 68
6 9/13 69 8/9 88 8/13 62
7 18/20 90 15/18 83 15/20 75
8 91/107 85 65/91 71 65/107 61
9 12/20 60 7/12 58 7/20 35
_________________________________________________________________________________________________________________________________________________________________________________________________________________
Total 268/323 83% 197/268 74% 197/323 61%
Patterson, 1990, University of Kentucky
_________________________________________________________________________________________________________________________________________________________________
DAS 93-44 Reproductive management systems for artificial insemination of dairy heifers 8
AI FOR HEIFERS (continued)
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Although there were no controls in this field Although this is a 31-day program, the
study, the results clearly show that excellent advantages of the MGA + PG system are the
estrous response and acceptable conception and good estrous response, superior fertility, ease of
pregnancy rates were obtained. Researchers felt administration of hormones, and reasonable cost.
that differences among herds may have been due Special premi