Reference Library

"Artificial Insemination"
by Stuart J Burns D VM

Animal scientists today are working on many technical "gee whiz" concepts that will affect cattle breeding in the future. Interesting, but probably won't put that 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 (Al) and the role in breed development. The use of Al in purebred breeds of cattle is reported to 11% to 13% of calves registered. The use of Al in Texas Longhorns is less than average as shown in the graph below.

Undertaking an Al program may cause some of us to be intimidated. The reasons Al are worth review. All 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 complement 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. Al 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.

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 be well fed so she will reach 213 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 Al 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...

1. Most cows will not rebreed during the first 60 days after calving. (Texas Longhorn cows seem to beat this time
very often).

2. The specific calving interval means that less time is required for heat detection and the success of detection will
be higher.

3. The nutritional demands can be addressed on a herd-wide basis instead of one individual cow at a time.

4. 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.