Within the lifetimes of many current U.S. dairy producers, artificial insemination (AI), sexed semen, embryo transfer (ETU), ovum pick-up (OPU), and in-vitro fertilization (IVF) all have evolved to enhance dairy cattle reproduction.
Now, individual-cow monitoring technology is being used to drive the next wave of dairy reproductive improvement: Targeted Reproductive Management (TRM).
Dr. Glaucio Lopes, who leads the monitoring success team for Merck Animal Health, USA, , explained that TRM leverages individual-cow data that detects estrus activity to more selectively and effectively implement hormone-driven estrus synchronization protocols.
Using activity monitoring tools like SenseHub® Dairy, one example of TRM stratifies cows into two groups early in lactation: those that expressed a strong, spontaneous estrus cycle before the end of voluntary waiting period (VWP), and those that did not. If they did not, they are enrolled immediately in a fertility program like Double Ovsynch that includes timed artificial insemination at the end. If they did, they are assumed to be more naturally fertile, and are allowed more time to be bred upon observation of another heat cycle. If that doesn’t happen within a prescribed number of days, they too are then enrolled in a synchronization program.
In short, TRM provides more time for cows that expressed early lactation natural estrus before beginning hormone-based synchronization, and less to those that did not – essentially targeted the use of manual synchronization and timed insemination on cows that need it most.
Lopes said one TRM study showed researchers were able to decrease the overall use of reproductive hormones by 57%. At the same time, the likelihood of pregnancy at 305 days in milk was increased in second-lactation and older cows that did not show strong signs of estrus early postpartum.
Enrolling fewer cows in hormone-based breeding programs not only lowers drug costs and saves on labor, but also creates fewer physical disruptions. More cows are allowed to carry out their natural behaviors of eating, drinking, and resting without spending time in headlocks.
Researchers at the University of Florida put the principles of TRM to the test in two north-central Florida Holstein herds, the results of which were recently published in the Journal of Dairy Science. Dr. Ricardo Chebel and his team evaluated 539 first-calf heifers and 941 second-lactation and older cows.
The more mature cows were assigned a VWP of 40-41 days in milk, while the first-calf heifers had a VWP of 54-55 days in milk. Half of the animals in each age group were treated as a control group and enrolled in Double Ovsynch regardless of estrus behavior. This occurred at 68-69 days in milk for the older cows and 82-83 days for the first-calf heifers.
In the TRM group, older cows that had expressed estrus within the VWP were inseminated upon detected estrus starting at 50 days in milk, and first-calf heifers starting at 64 days in milk. If they had not been detected in estrus during the VWP, they were enrolled in Double Ovsynch at the same time as their corresponding parity in the control groups.
Re-insemination of open cows in the control group was based on visual or patch-aided estrus detection, while TRM cows were re-inseminated based on activity monitor feedback for estrus activity. This resulted in the open TRM animals being re-inseminated more quickly.
Among the results: more cows from the TRM group eventually calved and started a new lactation compared to the controls (82.6% versus 77.2%), and fewer of them were sold (15.5% versus 20.8%). The TRM cows also used an average of just 4.5 doses of reproductive hormones, compared to about 10.1 doses for the control cows.
Chebel noted that in this particular experiment, TRM improved gross profit per cow by $108 per head compared to the control animals. He said factors that contributed to that figure included improved pregnancy success – regardless of parity -- that changed culling dynamics; fewer cow sales that led to reduced replacement costs; and increased calf value created by the ability to target strategic semen selection toward the most fertile cycles.
