It has been 20 years since the Ovsynch program was released to the industry. Since then, a lot has been learned about improving fertility, and 21-day pregnancy rates have increased from 14 percent to more than 30 percent.
“There are quite a few herds able to achieve that,” said Milo Wiltbank from the University of Wisconsin – Madison.
At the Vita Plus Dairy Summit, Dec. 9-10 in Baraboo, Wisconsin, Wiltbank explained the 21-day pregnancy rate is based on insemination intensity (service rate) and how many of those result in pregnancy (conception risk). If the pregnancy rate is low, producers should look at those two areas to see which one needs improvement.
One way to improve the service rate is to implement an Ovsynch protocol. With Ovsynch, “we bred them earlier and bred them more efficiently so we increased service rate, but there was no effect on conception risk,” Wiltbank said.
He added, “It can even decrease conception risk in animals with high fertility, like heifers.”
The Ovsynch program typically yields a 32 percent conception risk because there is a certain percentage of the cows correctly synchronized by Ovsynch and a certain percentage not correctly synchronized. It has to do with where the animals are in their cycle when you happen to start the protocol.
“We figured out there are just three things we have to know about synchronization,” Wiltbank said. “This is important because you can do this on your farm and be able to improve your fertility.”
- At the prostaglandin (PGF) shot, there needs to be a corpus luteum (CL) present and higher progesterone. About 20 percent of the animals are not correctly synchronized at that stage, and they have a 10 percent conception risk.
- At the second gonadotropin-releasing hormone (GnRH) shot, there needs to be low progesterone. According to a study, there are 15 to 25 percent of animals that don’t have low enough progesterone, and their conception risk is less than 10 percent.
- Does the cow ovulate to the last GnRH? Wiltbank said 5 to 15 percent of animals will not ovulate at this step.
He figured there are 50 percent of animals correctly synchronized with Ovsynch and about 50 percent not correctly synchronized. The ones that are correctly synchronized have about 60 percent conception risk, and the ones that are not correctly synchronized have about 10 percent conception risk.
With that knowledge, more protocols have been developed in order to synchronize 90 percent of the cows.
- Studies have shown Presynch-12-Ovsynch improves conception risk 12 to 14 percent compared to Ovsynch.
- Presynch-11-Ovsynch with all timed A.I. has a higher conception risk of 49.2 percent compared to breeding to estrus detection at 37.9 percent because it allows cows to be bred when they are most fertile.
- Double Ovsynch helps to solve the problem of cows that are not ovulating. If a farm is not treating with some kind of GnRH or CIDR before 60 to 70 days in milk, Wiltbank said, about 23 percent of cows will be anovular at that time.
When checked for a CL after the second GnRH in double Ovsynch, almost all of the animals (94 percent) have a CL, compared to Presynch-Ovsynch with 74 percent having a CL present.
“We got quite a bit better fertility when we use double Ovsynch versus Presynch-12-Ovsynch,” Wiltbank said.
- Adding a second prostaglandin to double Ovsynch can increase conception risk from 34 to 37.7 percent. “You can’t expect miracles, but it’s going to improve fertility because there’s a percentage of animals that don’t regress their CL, and this will cause the CL to regress,” he said.
These protocols have made an impact, improving the 21-day pregnancy rate from 14 percent to 26 percent, but how are herds achieving 30 percent?
Wiltbank said one way is to do a double Ovsynch followed by a Resynch-25+CL check. A GnRH injection is given to all animals on day 25, and on day 32 they come in with the pregnancy check and a veterinarian evaluates the ovaries for a CL.
If they don’t have CL (about 15 to 20 percent of the animals), a CIDR-synch program is used for the next week to bump the conception rate.
With this program, Wiltbank said the conception rate could be above 40 percent and the 21-day pregnancy rate at 32 percent.
“Protocol is not everything,” Wiltbank said. Producers also need to “optimize other aspects on the farm.”
To improve reproduction, there are a lot of different parts to the puzzle, including genomics, reproductive management programs, cow comfort, A.I. skill and nutrition during the dry period, transition period, before A.I. and after A.I.
While some farms may shy away from a more extensive synchronization program due to cost, an example shared by Wiltbank showed it may actually yield some savings.
He compared two farms of similar size and milk production (Table 1).
Farm 1 had a voluntary waiting period of 40 days in milk and did a lot of breeding based on heat detection. It had a 21-day pregnancy rate of 16 percent.
Farm 2 had a more intense synchronization program and a voluntary waiting period of 76 days in milk. It had a higher service rate and much higher conception rate, which led to a pregnancy rate twofold higher than Farm 1.
Both farms had roughly 360 pregnancies recorded during the time period analyzed; however, it took Farm 1 almost 1,100 breedings to achieve that while Farm 2 only had 730 breedings.
Farm 2 was using more PFG and GnRH, costing about $10 more per cow for that producer. Both producers were using really good bulls, but since Farm 2 was using fewer straws per cow, it was saving $14.20 on semen costs and ended up more than $4 per cow ahead of Farm 1.
“Amazingly enough, this aggressive program is actually cheaper, at least from a hormone standpoint and straws of semen standpoint when you add that up,” Wiltbank said. “They’re making a lot of money, believe me. Just this 21-day preg rate is probably worth $150 to $200 per cow per year.”
Paying attention to fertility and other areas on the farm in order to make a breeding program as efficient as possible will continue to move the needle when it comes to 21-day pregnancy rates. PD
-
Karen Lee
- Editor
- Progressive Dairyman
- Email Karen Lee
