Reference Library
Artificial Insemination
The Vet's Bag, May 1997
by Stuart J. Burns, D.V.M.
The column printed in the Trails' Herd Sire Issue provided
a view of the future with all the technical "gee whiz"
extra fancy calf in your show string for several more years.
It is time to return our attention to the present and examine
artificial insemination (AT) and the role it plays in breed development.
The use of Al in purebred breeds of cattle is reported to produce
11% to 13% of calves registered. The use of Al in Texas Longhorns
is less than industry average as shown in the graph below.
Undertaking an Al program may cause some of us to be intimidated.
The reasons to utilize Al are worth review. AH of us have seen
catalogs containing cattle that have no recognizable ancestors
until the third or fourth generation is reached. Such cattle
usually bring a long hard sale day with little economic reward
to their breeders. The first compelling reason to use Al is to
improve the economic value of your calf crop. Weigh the cost
of a unit of semen on that bull with high "name recognition"
compared to the thousands of dollars it took in advertising and
hauling to earn that recognition. The selection of a special
bull to compliment an individual cow is possible with Al. This
may allow creation of a "top class" calf while the
owner's herd bull may only be able to sire a "real nice
one" out of that same cow.
Small breeders sometimes are tempted to lease or borrow a
bull rather than own one, which opens the door for some unwanted
diseases. Semen processed under the guidelines of the Certified
Semen Services (CSS) will prevent the introduction of Tuberculosis,
Brucellosis, Trichomoniasis, Vibriosis, Leptospirosis and Paratuberculosis.
Another benefit of Al is the ability to restrict the calving
interval so that calves can be managed as a single group.
With these compelling reasons to utilize Al, how could anyone
not elect to proceed? As is usually the case, the good things
worth having are accompanied by increased difficulties in obtaining
them. A successful Al program is more labor intensive, including
heat detection and insemination. The skill of the technician
and the manager's dedication to the goal of success are critical
to produce satisfactory results. AI will add costs for this labor,
for the insemination service, plus the semen costs. Depending
on the design of the program, repeated attempts to Al may prolong
the calving season as cows failing to conceive require another
cycle of opportunity. About 50-60% of the cows should become
pregnant each cycle they are bred. There may also be some drug
expenses if synchronization products are used. Central to any
Al program, and frequently not available to owners of small herds
of cattle, is a facility that is tall and strong enough to assure
that any cow placed therein will still be there when the inseminator
arrives!
The technical details of an Al program will come in the June
issue. For now we must first look at some foundation work that
should be done to assure that 50-60% conception rate per cycle
bred. Cows going into an Al program must be on an adequate plane
of nutrition. The most critical time of nutritional demand is
during the last two months of pregnancy through re-breeding.
During this time best results are obtained if the cow is gaining
weight. Cows that are underfed may not show heat, may not ovulate
or may have a higher rate of early embryonic loss. The cow must
have enough energy to maintain herself {nurse her calf, and energy
to spare for the new pregnancy. Heifers find this a particular
challenge because they are still trying to grow themselves while
doing all the rest. If a heifer is to calve at 24 months, she
must he well fed so she will reach 2/3 of her mature weight by
15 months of age. Below this weight, the heifer is physiologically
unsuitable for breeding. She will also require significant feed
inputs to breed back. First calf heifers should be fed separately
from the main herd. At this point a practical cowman must begin
to weigh the cost of feed required to calve at 24 months of age
compared to the lower cost to just grow the heifer an extra six
months before breeding. This will put her first pregnancy at
a time when her energy demands for growth are less and her chances
for a timely conception upon re-breeding are increased. Heifers
in an AT program are best given a 30 day head start on the main
herd, for they frequently require more time to recover from their
first calf and become ready to rebreed. With this head start,
their second and subsequent calves will arrive on time with the
main herd and the calving period of the whole herd can be maintained.
It is very difficult to get a cost effective Al program started
in herds that do not have a restricted calving interval of about
2 to 2 1/2 months. This specific calving interval is desirable
because...
- Most cows will not rebreed during the first 60 days after
calving. (Texas Longhorn cows seem to beat this time very often).
- The specific calving interval means that less time is required
for heat detection and the success of detection will be higher
- The nutritional demands can be addressed on a herd-wide basis
instead of one individual cow at a time.
- There is less labor expense as more cows are observed in
a shorter period of time.
Remember that cows having a difficult birth will have a 3-8%
reduction in conception rates. The heavily milking cows that
produce the heavy 205 day weights will require more energy to
meet this demand along with becoming pregnant again. If these
demands are not met, these cows may not conceive on schedule.
The general approach to feeding the Al herd is to have the group
in moderate finish at 7 months gestation and increase the feed
or grass so the herd is gaining weight while calving and breeding
back. This is what is meant by the term "flushing".
If the cows are already heavy, there is no benefit to be gained
by flushing.
Particular attention should paid to vitamin A and phosphorous
levels as the requirements of these two nutrients will nearly
double during late pregnancy and lactation. Vitamin A will be
abundant in good quality alfalfa hay or spring growth pastures
while phosphorous is usually high in all feed grains. Herds maintained
on forages alone should have a balanced mineral source available
free choice to provide adequate phosphorus.
Next month we will outline an Al program with its technical
details, including synchronization, heat detection and Al techniques.
Reprinted with
permission of Texas Longhorn Trails Magazine and/or TLBAA (Texas Longhorn
Breeders Association of America)
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