Dr. George Perry – 4/5/2012
This article written with contributions from Jim Krantz.
Artificial insemination (AI) is one of the most powerful tools available for genetic improvement in the cowherd. However, success of any AI program requires attention to details as well as identifying target goals for pregnancy rates, resources available, and recognizing critical factors that are limitations to those expectations.
Expected Pregnancy Rates: Pregnancy rate is the product of estrous detection rate and conception rate. It is important to remember that a pregnancy rate of 60 to 70% to a single insemination is good for either AI or natural service. For natural service, a pregnancy rate of 60 to 70% is normal for the first 21 days of breeding season, if all bulls are fertile and 100% of the heifers and/or cows are cycling. However, it is a very rare situation to have 100% of all the heifers and/or cows cycling at the start of the breeding season. For an AI program, a synchronization protocol can be selected to help induce heifers and/or cows to cycle. Therefore, with attention to several details AI pregnancy rates of 50 to 70% can be achieved within 1 to 3 days of the breeding season with most of the recommended synchronization protocols.
Resources Available: Facilities, experience, manpower and available feed resources contribute to the decision of utilizing AI in the breeding program. Adequate facilities, does not mean that an investment in “steel” is a prerequisite. In fact, properly designed wooden corrals and sorting pens may be desirable providing a quieter working environment. Most AI programs, whether synchronization is or is not involved, demand additional, skilled labor as proper handling of the cattle can have a dramatic impact on success rates. Pregnancy rates are correlated to the nutritional status of the female. If cows are bred near an existing facility, grazing paddocks must be sufficient to support the number of cows/heifers that will be grazing during the breeding season.
Critical Success Factors for AI: When it comes to reproductive management, exceptional performance in one area will not compensate for the mistakes you make. Reproductive success will never be better than performance in the weakest area:
- Temperament- Temperament will vary among animals and is both a safety and production (growth, reproduction, carcass quality) issue. Recent work done at Organ State has reported a correlation between temperament and pregnancy success. Beef cattle with an excitable temperament have been reported to decrease the probability of pregnancy during the breeding season compared to calm herd mates.
- To achieve good pregnancy rate estrus synchronization protocols must be followed precisely. To minimize the probability of making a mistake, a good practice is to write each of the days of treatment, the product name, dose to be administered, and the day of insemination on a calendar and ask a trusted veterinarian, extension specialist, or AI company representative to review it before beginning the protocol.
- Nutrition- Replacement heifers should be developed to an appropriate target weight (65% of mature weight) prior to the breeding season. Cows should also be fed to attain adequate body condition prior to calving (BCS ≥ 5). Therefore nutrition prior to the start of the breeding season is of obvious importance. However, nutrition following breeding can also have a direct affect on embryonic development and survival. Any dramatic changes in diet or feed intake following breeding that result in weight loss can negatively impact pregnancy rate and should be avoided.
- Vaccination Program-A prebreeding vaccination program in combination with careful attention to biosecurity practices and reducing stress/disease transmission within a herd should be included in a herd health program. Several studies have reported injection of naive heifers with a MLV virus around the time of breeding resulted in ovarian lesions and decreased pregnancy rates. Therefore, general recommendations for prebreeding vaccinations are both heifers and cows should receive vaccinations 45 to 30 days before breeding.
- Post-AI shipping- Recent studies in Montana have reported that transporting cattle on a trailer decreased pregnancy rates by about 10% between days 5 and 42 after insemination and by 6% between days 45 and 60. The best time to ship cattle is before synchronization or within 4 days of breeding.
- Proper insemination technique- If you choose to artificially inseminate heifers or cows yourself, remember that the location of semen placement within the reproductive tract will have a significant impact on pregnancy rates. It is important to deposit the semen in the body of the uterus (target area) and not the cervix. Deposition in the cervix will significantly reduce the pregnancy rates. Furthermore, semen handling should not be overlooked, since improper handling of semen can reduce semen motility and also greatly reduce pregnancy rates.
While artificial insemination provides access to the world’s greatest genetics, this management tool can be a costly and time-consuming investment if not approached with attention to detail. Success with it requires homework, patience and knowledge of researched, procedural fundamentals.
For more information related to beef reproduction see your local extension field or state specialist and continue visiting www.igrow.org for future articles on beef reproduction.