Ovsynch protocols and timed AI can eliminate the need for heat detection. In today’s beef and dairy economies, improving reproductive efficiency represents one of the best opportunities for boosting profits. A variety of new technologies and, in some cases, existing but under-utilized technologies offer potential for driving those improvements. Naturally, though, they sometimes come with tradeoffs or caveats.
Protocols for artificial insemination (AI), for example, continue to evolve and become more specific to beef versus dairy operations and heifers versus mature cows.
George Seidel, PhD, says progressive beef operations and veterinarians increasingly are moving away from synchronizing estrus toward synchronizing ovulation for timed AI. These ovsynch programs involve timed injections followed by breeding without heat detection. Seidel, who is a distinguished professor at Colorado State University’s College of Veterinary Medicine, also operates a ranch, Rabbit Creek Angus near Livermore, Colo. He has tested ovsynch protocols in his own herd and helped introduce the system to the beef sector. A number of ovsynch protocols are available, and Seidel notes the recommended protocols for heifers differ from those for lactating cows.
At Colorado State University, George Seidel conducts research on sexed semen and synchronization protocols for dairy and beef cattle. University of Missouri animal scientist Dave Patterson, PhD, says timed AI is just one existing technology the beef industry has been slow to adopt. He references Missouri’s Show-Me-Select heifer program as an illustration of trends in beef reproduction. Veterinarians, he says, play a key role in the program.
Show-Me-Select includes a uniform health program geared toward long-term reproductive efficiency. An exam four to six weeks before breeding includes a reproductive tract scoring (RTS) system and a determination of the percentage of heifers cycling.
The scoring system provides a 1 to 5 rating, with 1 representing an infantile reproductive tract and 4 to 5 representing a heifer that has reached puberty and is cycling. Patterson recommends initiating a progestin-based protocol (MGA or CIDR) to synchronize estrus in heifers when 50 percent of the heifers in a group score 4 or 5. Veterinarians also obtain pelvic measurements at the time the pre-breeding exams are performed. Pelvic exams are used as a screening tool for heifers enrolled in the program and are highly correlated to RTS. The combination of service-sire requirements for birthweight or calving-ease-direct EPD and pelvic measurements have dramatically reduced both the incidence and severity of calving problems for heifers enrolled in the program.
Producers wait two weeks after timed AI to turn bulls in with the heifers. They then use ultrasound scanning at 90 days post-breeding to check pregnancy, fetal age and, in some cases, sex of the fetus. This allows participants to qualify heifers for the higher program tiers, with certification of pregnancy through AI to high-accuracy sires.
Premiums for qualified heifers are helping drive demand for ultrasound scanning. In Show-Me-Select sales from fall 2010 through 2012, qualified, natural-service bred heifers sold for an average of $1,638, andthose with verified AI pregnancies averaged $1,830. Those heifers that were AI sired from high-accuracy sires that qualify for Tier 2 in the program and were carrying AI-sired pregnancies averaged $1,968.
With timed AI, even if half of the females are pregnant on the first day of the breeding season, there is huge value to the producer in terms of a more uniform calf crop and long-term fertility in the cow herd. And 70 percent conception rates are possible with a good synchronization program.
Patterson says veterinary involvement in RTS, pelvic exams and ultrasound scanning helps producers refine management practices and identify selection or culling opportunities. The program also has led to more use of AI in heifers and emphasis on synchronization protocols that work within individual production settings. These services offer opportunities for veterinarians to become more involved in reproductive management in clients’ herds and provide significant value to producers.
These systems are not new, but the Show-Me-Select program has helped raise awareness. “We have tools available today that are not being applied in the field,” Patterson says. With production costs high and margins tight for cow-calf producers, improvements in reproduction, coupled with adding value to calves through uniformity and genetic merit, offer the best opportunity to improve profitability.
Tradeoffs in preg testing
Non-pregnancy diagnosis is a key role for veterinarians in dairies, and University of Wisconsin dairy scientist Paul Fricke, PhD, says even that common practice continues to evolve. Ultrasound has come into common use over the past 15 years, and initially, people perceived early diagnosis as a key advantage. Fricke warns, though, that prior to 30 days post-breeding, a veterinarian could see a corpus luteum and fluid in the uterus but no embryonic heartbeat. Typically, someone is nearby with a shot of prostaglandin to begin synchronizing open cows, so the veterinarian likely diagnoses the questionable cow as pregnant even though she is open due to embryonic death. In the dairy’s records, these errors tend to artificially inflate conception rates and also abortion rates.
Fricke says he is trying to move dairies away from using ultrasound before 30 days post-breeding, with 32 days preferable and 39 days better for accurate non-pregnancy diagnosis and re-synchronization. Most importantly, diagnosis using ultrasound should be based on visualization of a corpus luteum, fluid in the uterus and detection of an embryo with a heartbeat.
Tests using pregnancy-associated glycoproteins (PAGs) offer a new option for pregnancy testing using blood or, in one case, milk samples. These tests are 95 percent accurate or better, but the samples need to be taken at least 30 days post-breeding and 60 days post-calving, Fricke says. The PAGs reach high levels in late gestation and take up to 60 days post-calving to be removed from maternal circulation, so earlier sampling can result in a false-positive diagnosis. Evolution of these tests could allow earlier testing in the future.
These tests offer convenience and accuracy but also some challenges, since animals need to be sampled, samples identified and shipped to a lab and results linked back to individual animals. Palpation or ultrasound provide cow-side diagnosis. Fricke foresees blood or milk tests eventually moving toward cowside analysis and diagnosis.
Accelerated progress
Patterson says genomic tests continue to evolve and offer potential to significantly improve heifer fertility, reproduction rates and other economic traits in dairy and beef herds. Seidel agrees, saying dairies especially apply genomic information to breeding programs.
In the past, Seidel says, national bull studs might sample 1,000 bulls based on pedigree. It would then take four years to collect progeny data on 50 or more milking daughters from each bull and narrow the list to 100 AI studs. Today, by using genomic information along with pedigree, breeders have much more accurate information on production traits when a bull is born than they did with pedigree alone, and can discard 80 percent of the candidates at birth. The genomic predictions are equal to progeny data from 20 to 40 daughters, and any decline in accuracy is offset by the reduced generation interval.
Using young bulls in an AI program might sacrifice some accuracy, but on average, they are better bulls, and genomic-enhanced selection provides a considerable cost savings compared with keeping bulls for four years before collecting large amounts of semen.
In fact, Seidel says, we now can learn the genomic value of a bull at the embryo stage, with a biopsy shortly after fertilization providing cells for genomic evaluation. About 80 percent of dairy bulls in AI studs are produced using embryo transfer, so genomic testing of embryos can reduce the cost of maintaining recipient cows.
Seidel also notes that without genomics, the dairy industry had relatively scant data on females. Genomic information on females allows more strategic matings to produce the highest-value bulls and heifers. “If the youngest cattle in the herd aren’t the best in the herd, you are going backward,” Seidel says.
Early breeding
Other technologies can reduce the time for getting top genetics into the herd. Currently, Seidel says, breeders begin collecting semen from a young bull at 10 to 11 months of age. Researchers now are studying systems to reduce the time to puberty, potentially allowing collection at 8 months or earlier.
For a progressive bull stud, bringing semen to market from bulls at 8 months of age rather than 11 could be worth hundreds of thousands of dollars. The generational interval is shorter and progeny data becomes available sooner.
Similar work is underway with heifers. Seidel and his colleagues at CSU have successfully fertilized and transferred embryos from 5-monthold heifers, using older females as recipients.
Behavior monitoring in dairy cows, and potentially in-line monitoring of progesterone in milk, can aid decisions in reproductive management. Monitoring for reproductive management
Fricke says activity monitoring has come into fairly common use in dairies for estrus detection. These systems, which typically employ a radio-frequency tag mounted to a collar, also can detect signs of sickness in some cases. The systems monitor cow movement and, after establishing a baseline of typical activity, identify upward trends in activity that could indicate an animal coming into estrus. He says these systems work but with limitations.
Fricke and his team conducted tests showing activity monitoring detects estrus in about 70 percent of cows at the end of the waiting period. Another 10 percent ovulate without showing signs of estrus and 20 percent are not cycling. Dairies that use activity monitoring exclusively, without synchronizing cows, can see pregnancy rates decline, he says. Ideally, activity monitoring should be used along with a synchronization program, with about 70 percent of cows bred to estrus and 30 percent bred with timed AI.
Monitoring systems involve more initial investment and depreciation while timed AI incurs more ongoing costs, but Fricke says costs balance out over time. Early detection of illness could provide a value advantage for activity monitoring.
Progesterone monitoring, Fricke says, offers substantial potential for managing reproduction in dairies. Fluctuations in progesterone levels in blood or milk could help determine cyclicity status, trouble-shoot synchronization protocols, diagnosepregnancy or non-pregnancy and identify pregnancy loss.
Samples taken during a synchronization protocol can help identify which cows are not cycling, and by sampling at breeding and again seven days later, dairies can determine which cows did not conceive. Currently, samples need to be sent to a lab at a cost of about $5 per sample. Fricke says dairies could benefit from some means of serially measuring progesterone across the herd. He envisions development of in-line systems for testing milk without a per-sample cost. Progesterone monitoring, he says, will not replace other types of pregnancy tests or synchronization but can complement those tools and assist in management decisions.
Sidebar: Remove the cow from cow-calf production?Convergence of reproductive technologies could allow a radical shift in the beef-production system — virtual elimination of the cow herd. In conventional systems, producers essentially “store” cows over the winter every year, at considerable expense, says George Seidel, PhD, a rancher and reproductive physiologist at Colorado State University.
In an alternative system, producers could use ovsynch along with sexed semen to produce a herd of first-calf heifers. After early weaning, the dams go to the feedyard for finishing as long yearlings and their heifer calves are raised as replacements. The heifers go to slaughter at about 30 months of age.
Everything on the ranch is growing in this system, Seidel says. All the females are gaining weight and gaining value until sale time, unlike cows that depreciate over time. The availability of proven calving-ease sires minimizes problems with calving heifers. Also, Seidel adds, heifers are typically the easiest females to get bred — the system avoids the “sophomore slump” that often affects females nursing their first calves. There is no castration and no old, lame cows to manage on the ranch.
Seidel, who often conducts CSU research trials in his own herd, currently is testing this system with a group of 54 heifers on his ranch, Rabbit Creek Angus.
The system will require adding back some females to maintain a stable breeding herd. Some heifers will fail to produce a calf, and heifers bred to cleanup bulls would produce some male calves, as would the AI heifers, as sexed semen currently has an accuracy rate around 90 percent. Seidel, who has been closely involved in the development of sexed-semen technology, expects that accuracy rate and the fertility rate of sexed semen to improve over time. Overall, he expects a producer would need to add back one-quarter to one-third of the heifer herd each year. Any down sides to the system should be overcome by gains in production efficiency. Seidel expects the system to produce 30 percent more beef with the same feed requirements and lower water use compared with conventional cow-calf production.
Source: Bovine Veterinarian
