Animal Health
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Researchers Working To Improve Cattle BreedingBy Linda Breazeale MISSISSIPPI STATE -- Mississippi dairy and beef producers will benefit from efforts of Mississippi Agricultural and Forestry Experiment Station researchers attempting to synchronize ovulation in heifers to improve reproductive performance and increase profitability. Methods are in place to synchronize estrous, or heat, but not to control ovulation, or release of the egg. Ovulation typically occurs 24 to 48 hours after a cow comes into heat. In MSU's Animal and Dairy Science Department, MAFES animal and dairy researcher Peter Ryan is working with other scientists to determine the best method for using a slow-release drug delivery system to cause a group of heifers to ovulate at the same time. "In dairy heifers, injection of gonadotropin releasing hormone (GnRH) can be used to synchronize ovulation, but the time from GnRH administration to ovulation is extremely variable," Ryan said. "This variability contributes to low conception rates in heifers that are on an ovulation synchronization treatment." The researchers want to find out if a controlled release drug delivery system will improve the response to GnRH. Their efforts are jointly funded by MAFES and Thorn BioSciences, the producer of the slow-release hormone therapy. Productive physiologist and endocrinologist Scott Willard said finding an effective slow release system will reduce the number of injections required for the synchronization process and ultimately save cattle producers time and money. "By tricking them into ovulating when we want them to, we can compress the cycle into a shorter window and eliminate the need to see a behavioral estrous," Willard said. "Currently, farmers watch for behavioral signs that a cow is in heat, and some may not show those outward signs." The researchers are trying to create a nine day protocol that will take the guesswork out of the formula. "Although observation for estrous is relatively easy to work into the management scheme for lactating dairy cows that are milked two to three times daily, additional effort is needed for heifers because they are not observed as frequently," said John Fuquay, professor emeritus of reproductive physiology. Dairy nutrition and physiology specialist Bill Tucker said cattle have a narrow window of opportunity for breeding. "When you are busy with other chores, it is easy to miss signs of heat," Tucker said. "Ovulation synchronization is not just important for heifers, but for lactating cows as well, since milk production begins dropping off if the cow does not become pregnant in a timely fashion." One aspect of the ovulation research included the testing of a special electronic heat detection system. During the study, researchers investigated various injection intervals for the timing of ovulation. Their goal was to bring together a group of heifers at various stages of their estrous cycle and begin hormone injections. They then followed a prescribed protocol for a specific length of time and identified the ideal time to artificially inseminate. Ultrasound and reproduction management specialist Allen Williams said developing an effective method to synchronize ovulation will benefit dairy producers, who use artificial insemination almost exclusively, but will have even greater potential for beef producers. "The benefits in the dairy industry are great, but you could magnify those benefits by 10 in the beef industry," Williams said. "Only about 6 percent of beef producers use artificial insemination for their herds. Timing is much harder for beef producers." Dairy animals are observed closely twice a day, but beef producers work their animals much less often. If a successful pregnancy depends on a farmer observing the behavior of an animal in heat, the odds are not very good. Williams said hormone therapy and artificial insemination are economically beneficial for cattle producers. The cost of synchronizing estrous, buying semen and inseminating cattle is $26 to $35 per pregnancy. Using a bull will cost a producer about $30 to $32 per pregnancy. "Artificial insemination allows herds to make much faster genetic progress, and producers can concentrate the breeding and calving seasons," Williams said. The animal scientists agreed that the study and similar efforts could not be conducted without the expertise each researcher brings to the table and the assistance of graduate students. "Any one of us, by ourselves, would have a tough time trying to conduct these studies. In fact, we couldn't do it," Williams said. Released:
April 24, 2000 |
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