During the past 30 years, a number of factors have contributed to the modern dairy cow showing decreased signs of estrus (“heat”). It has become harder to accurately identify cows to breed and, therefore, also harder to achieve pregnancy.
Not surprisingly, various breeding programs have developed over this time period to help address this concern. Many of these programs are referred to as “synch” programs because they enable producers to synchronize the ovulations of the cows, making timed-artificial insemination (AI) breedings possible. The plethora of options available may result in producers finding themselves feeling like everything but the kitchen “synch” has been thrown at them.
“The menu of program options can be very confusing and encourages the idea that the newest, latest synch will be the best program yet. This may not be the case for that dairy and a change may actually result in poorer reproductive efficiency. Neither is it true that any one ‘cookie cutter’ approach will work predictably on every dairy,” said Gavin Staley, veterinarian and senior fresh cow reproductive manager with Pfizer Animal Health. The most important decision to make is which program can be reliably and reasonably implemented, within the existing constraints of dairy management, with outstanding compliance, again and again and again.
“Synchronized, hormone-based breeding programs have revolutionized dairy reproduction and management efficiency,” said Staley. “They allow producers to reduce the interval between calving and first-service artificial insemination and also manage the subsequent breedings.”
That first postpartum service is a golden opportunity to improve breeding efficiency and achieve maximum pregnancy rates on the most possible cows as soon as they reach the voluntary waiting period (VWP). “These initial synchronized breedings tend to stamp a synchronized shadow on subsequent breedings too. This means the initial investment has an ongoing payback,” said Staley.
To help dairy managers choose the best program for their herds, Paul Fricke, professor of dairy science at the University of Wisconsin, provides the following primer regarding the most popular dairy breeding protocols. All of the programs incorporate gonadotropin-releasing hormone (GnRH); prostaglandin (PGF2α); and timed artificial insemination (TAI).*
Protocol: GnRH----7 days----PGF2α----56 hours----GnRH----12-16 hours----TAI
Benefits: Developed at the University of Wisconsin-Madison, this program is the first synchronization program to successfully incorporate timed AI and eliminate the need for visual heat detection. The Ovsynch protocol ensures that all cows on the program are inseminated at the end of the protocol.
Protocol: GnRH----7 days----PGF2α----48 or 72 hours----GnRH + TAI
Benefits: By inseminating cows immediately after the second GnRH shot is administered, this program simplifies the Ovsynch protocol by requiring one less restrainment of the cow. While advantageous from a management standpoint, the implementation of Cosynch has been shown to negatively affect conception rates compared to the standard Ovsynch protocol.1 The trade-off between convenience and results should be evaluated when considering this program. Table 1 (below) shows a comparison of reproductive results at various breeding times relative to the second GnRH injection.
Protocol: PGF2α----14 days ---- PGF2α----12-14 days----GnRH----7 days---- PGF2α----56 hours----GnRH----12-16 hours----TAI
Benefits: Two set-up shots of prostaglandin, administered 14 days apart, help to remove randomness in the estrous cycle and ensure that most cows are at the correct stage of estrus to respond to the Ovsynch protocol. In one study of more than 500 cows, conception rates on first-service AI improved from 29 percent for Ovsynch to 43 percent for Presynch.2 The initial Presynch protocol was developed using an interval of 12 days between the second prostaglandin shot and the first GnRH shot. Subsequent studies have used a 14-day interval to allow the first 4 shots to be administered on the same day of the week and no significant effect on conception rates were observed. Because of the length of the protocol, Presynch should be used only for cows at their first postpartum AI service.
Ovsynch + progesterone
Protocol: GnRH + progesterone insert----7 days---- PGF2α + Remove progesterone insert----56 hours----GnRH----12-16 hours----TAI
Benefits: By adding progesterone within the Ovsynch protocol (and moving the prostaglandin shot up by 1 day), a steady dose of progesterone is delivered to suppress estrus during the first 7 days of the program. This program has been found to be especially successful for the re-synchronization of cows diagnosed open at pregnancy check.
Fricke recommends that the ultimate selection of a synchronization program should be based on the herd’s reproductive goals, labor availability, convenience of administration and cost considerations. Facilities, such as pen configurations and head locks, may need to be modified for successful implementation.
“Consult your herd veterinarian to weigh your options and decide what you want to achieve and which of the programs are practical and can be implemented,” advises Staley. “Regardless of the program selected, the most important factor will be that it is implemented correctly and consistently.”
*Note: The products listed in these reproductive programs may not be approved by the FDA for use in combination or program use. Consult your veterinarian for appropriate use of these products.
1 Pursley JR, Silcox RW, Wiltbank MC. Effect of time of artificial insemination on pregnancy rates, calving rates, pregnancy loss, and gender ratio after synchronization of ovulation in lactating dairy cows. J Dairy Sci 1998;81:2139-2144.
2 Moreira F, Orlandi C, Risco C, Lopes F, Mattos R, Thatcher WW. Pregnancy rates to a timed insemination in lactating dairy cows pre-synchronized and treated with bovine somatotropin: cyclic versus anestrus cows. J Dairy Sci 2000;83(Suppl 1):134(Abstr.).
Source: Pfizer Animal Health