Herd reproductive performance is critical to maximizing milk production but negatively correlates genetically to milk production. Reproductive performance needs to be assessed regularly with a recent paper from the University of Wisconsin-Madison identifying the 21-day pregnancy rate as the base of the farm reproductive management pyramid.
A 21-day pregnancy rate is the interaction between artificial insemination, AI service rate, and pregnancies per AI. The 21-day pregnancy rates allows you to continuously evaluate your reproductive performance as weather and feed change on the farm.
Over the last 20 years, a lot of research has gone into programs to improve reproductive performance. After the 21-day pregnancy rate, the pyramid moves to heifer management, then Genomic selection, after those three have been mastered it moves to the utilization of sexed and beef semen and finally IVP.
Before addressing synchronization programs, it is important to look at how well modern accelerometers are benefiting farms. In one study, 71% of cows were detected in estrus with 95% of them ovulating for true estrus.
Of the 29% that were not detected in estrus, a third of them did ovulate but were not detected by the activity monitoring system.
The first major estrus synchronization program with 100% AI service was the Ovsynch program. This protocol had similar pregnancies per conception to manual heat detection programs but decreased the average days to first service by about 30 days, and, in return, shortened the average days open by 19 days.
Over time, this program has been tested with the best variation being Ovsynch-56. This protocol has the GnRH being given 56 hours after the PGF2α and the Timed AI, TAI, 16 hours after the last GnRH.
While programs often get small adjustments on farm, the best success comes from following these recommendations, even though they do not match a 12-hour clock, they match the cow’s biology the best.
The next program is the Presynch-Ovsynch protocol which was developed to improve pregnancies per AI by increasing the proportion of cows between periods of five to 12 days in the estrus cycle at the beginning of the Ovsynch protocol. This additional PGF2α improved pregnancies per AI by 68% over Ovsynch and increased pregnancies per AI compared to manual heat detection by 13 percentage points.
One issue with the Presynch protocol was that it did not resolve the issue of anovular cows. To resolve the issue of anovular cows the Double-Ovsynch and G6G protocols have been developed. The Double-Ovsynch protocol increased pregnancies per AI by 10 percentage points over the Presynch protocol.
One study found no penalty breeding cows on a Double-Ovsynch protocol if they were bred early based on visual heat detection. We know that all cows are not biologically identical and heat detection systems may even benefit even these protocols.
When it comes to reproductive management, heifer programs should not be the same as cow programs. Only 2% of heifers in the US are inseminated for the first time based on a synchronization protocol. However, when using sexed semen, the decreased days open and can be achieved using a five day CIDR synch program, decreasing heifer raising costs by $13 per heifer when feed cost was $1.50 per day after including the additional labor and breeding cost of a five-day CIDR synch protocol.
While this study identified the 21-day pregnancy rate as the most important rolling factor there are other critical reproductive benchmarks. Many of the parameters build off of each other to achieve other parameters to achieve first service at 75 days in milk so that the average days open stay below 115 days. This should allow you to achieve a goal of a 13-month calving interval.
The farm conception rate at first service should be greater than or equal to 55% and all services greater than 50%. This parameter should be calculated for all AI technicians on the farm to make sure everyone is having success breeding cows.
Across all breeding programs, the farm needs to achieve a heat detection rate of at least 70%. Many timed AI programs allow for this goal to be achieved but don’t result in the goal of a 50% conception rate. The goal for herd reproductive culls per lactation is less than 8% and abortions should be below 5%.
Reproductive performance needs to be closely monitored year round but especially in the summer when cows are experiencing heat stress and feeds are changing as your new crop forages start to be feed.
