Just about anyone involved in studying bovine reproduction is familiar with the name of Dr. George Seidel. As a university distinguished professor at Colorado State University’s College of Veterinary Medicine and Biomedical Sciences, Seidel is a leading researcher in bovine reproductive physiology. His studies have included in vitro fertilization, embryo transfer, development of sexed-semen technology for cattle, cloning and methods for improving estrous synchronization and artificial insemination.
But while Seidel is well adapted to life in the laboratory and the halls of academia, he’s also at home on the ranch, where he applies some of the latest technologies to his registered Angus seedstock herd.
Rabbit Creek Angus is located outside Livermore, Colo., about 25 miles northwest of CSU’s Fort Collins campus. In the process of producing Angus seedstock and commercial calves, the ranch also serves as a real-world laboratory for Seidel to test new methods and for CSU students to gain hands-on experience in research and application of reproductive methods.
In his breeding program, Seidel says he selects for as much weaning weight as possible while keeping birthweights down. Most of his customers come to Rabbit Creek for bulls they can use with their replacement heifers, so they look for calving ease. And they typically operate in western short-grass rangeland environments where efficiency is critical. Selection pressure in some bull lines has increased milk production to a point where nutritional demands are too high in replacement females. They can’t maintain body condition on range conditions, resulting in high feed costs or declining reproductive efficiency. “In our country, we don’t send a lunch basket out with cows,” Seidel says. “They need to utilize the forage that’s available.”
Seidel and his team use artificial insemination in the registered cow herd, with cleanup bulls for females that don’t conceive after AI service. He matches AI sires to individual females based on their combined EPDs and physical traits.
As one of the pioneering researchers in the development of sexed semen in cattle, Seidel uses the technology in his own herd. “We use sexed semen on heifers for several reasons,” he says. One benefit — when selecting for heifer calves — is that birthweights average about 5 pounds lighter than male calves, meaning less calving difficulty in first-calf heifers.
Another reason is that fertility in heifers is usually a little higher than that of older cows. Sexed semen is about 90 percent pure, meaning 90 percent of conceptions will be the chosen sex. Conception rates with sexed semen, however, run a little lower, about 80 to 85 percent of those with conventional AI. Breeding heifers with sexed semen helps maximize first-service conception rates, while also offering more time for follow-up.
Seidel breeds replacement heifers three weeks earlier than the rest of the herd. Those not pregnant thus come into heat about the same time that the older cows are bred, and the crew then breeds those using conventional AI semen.
Finally, Seidel says, a sexed-semen program designed to produce heifer calves from heifers speeds genetic progress in the herd. Replacement heifers, being the youngest animals in the herd, should have the best genetics. Mating them with selected AI sires brings further improvement to the next generation of replacements, and using sexed semen nearly doubles the number of resulting heifer calves.
This spring, Seidel, in cooperation with CSU, initiated a test of a new estrous-synchronization protocol in his herd. The process, he explains, has two broad objectives.
The first, he says, is to get those females that are not yet cycling to cycle. The second objective is to improve convenience by synchronizing ovulation, thus allowing one-time timed AI without the need to check for heat.
The process involves using a CIDR — a progesterone-releasing intra-vaginal insert — and leaving the device in longer than normal. Cows also receive a GnRH injection in the middle of the CIDR process and a prostaglandin injection at the time that CIDRs are removed, three days prior to the timed AI. The test also includes a group of control cattle synchronized using more standard CIDR protocols.
Throughout the process, Seidel and cooperating CSU faculty involved graduate and undergraduate students who assisted with processing cattle, installing CIDRs, giving injections for synchronization, breeding cattle with AI and pregnancy testing.
It will be another month or so before he can evaluate the success of the experimental estrous synchronization protocol, based on pregnancy rates. But at AI time in early May, Seidel said the system looked promising, with physical signs suggesting most of the cows were in heat or coming into heat at the time of breeding.
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