As the dairy industry evolves and new strategies are required to improve herd performance, management, and sustainability measures, a potential approach to improve reproductive efficiency, optimize herd management practices, and increase profitability is Targeted Reproductive Management (TRM).

Also known as “precision” or “personalized” management, this approach to herd management consists of two keys steps.

First, subgroups of cows within a herd that share some biological or performance potential characteristics (predictors) associated with reproduction and performance must be identified (Figure 1). Data from these predictors must be available before key decision-making timepoints, such as the end of the voluntary waiting period (VWP), first service, pregnancy diagnosis, or stage of lactation. Examples of biological characteristics are genetics for fertility and milk production. An example of a performance potential characteristic is the ability to express estrus after the VWP.

Second, targeted management strategies specifically designed to optimize cow performance, herd profitability, or alternative metrics of interest (Figure 1) are implemented. Programs that prioritize insemination in estrus (AIE) or timed AI (TAI), increasing the economic value of offspring and reducing herd replacement costs through targeted use of sexed semen, beef semen, valuable high genetic merit bull semen, or embryo transfer are examples of TRM (Figure 1).

Ultimately, the expectation is that by tailoring reproductive management, greater gains in performance, management, or both, will be realized than if the whole herd is under similar management.

AUTOMATED ESTRUS ALERTS DURING THE VWP

We have known for a long time that expression of estrus in early lactation is positively associated with subsequent reproductive performance. Cows that have at least one estrus event before 50 to 60 days in milk (DIM) are more likely to show estrus again, are more likely to become pregnant to first service, and are more likely to be pregnant by mid-to-late lactation. We have confirmed and demonstrated this association in several studies.

Although dairies have mostly ignored expression of estrus in early lactation or during the voluntary waiting period (VWP), automated monitoring technologies to detect estrus have revived interest in monitoring this important indicator of cow reproductive performance. In dairies where cows have a sensor during the whole lactation cycle, or starting at calving, automated estrus monitoring systems enable recording estrus events easily and without extra labor. Thus, our research group has been exploring how farms could use automated estrus alerts collected during the VWP to implement TRM strategies.

An example of a TRM program based on estrus alerts collected during the VWP consists of providing different periods of insemination in estrus (AIE) to cows with or without automated estrus alerts (AEA) during the VWP. The idea is to provide more time for AIE to cows that had estrus during their VWP and less to cows with no estrus alerts.

While we expect cows with alerts to be more likely to express estrus again and to have good fertility if inseminated in estrus, the opposite is expected for non-estrus cows. As more of the estrus cows are expected to receive AIE, the beginning of the synchronization protocol for TAI is delayed (i.e., three to four weeks) so that fewer cows are synchronized and receive TAI.

Conversely, the TAI protocol is initiated earlier (i.e., about two weeks) in cows with no estrus to ensure they are inseminated sooner and that more cows benefit from the TAI program. This example program, which aims to prioritize AIE and target the use of TAI on cows that need it most, is what we usually call a “targeted predominant AI in estrus program” (Figure 2).

A recent experiment from our group evaluated reproductive performance of cows managed with a TRM program like the one in Figure 2. Cows with AEA (about 40 percent of all cows) collected up to 49 days in milk (DIM) by an ear-attached automated estrus detection system were given up to 31 days to receive AIE, whereas cows with no AEA during the VWP were given up to 17 days to receive AIE. Cows not AIE in both groups were enrolled in an Ovsynch protocol with progesterone supplementation (P4-Ovsynch) to receive TAI. The benefits and drawbacks of this program were compared with a program that used TAI after a Double-Ovsynch protocol and had a longer VWP for all cows. We used this program for comparison because it is one of the most effective to optimize first service outcomes of dairy cows when using intensive TAI programs is an option. 

As expected, for the TRM program, most cows in the group with AEA during the VWP received AIE (85 percent), whereas more cows (about 45 to 50 percent) received TAI in the group with no AEA. Thus, only a few cows needed TAI in the AEA during the VWP group and more cows benefited from TAI in the group with no AEA during VWP. 

Interestingly, the targeted predominant AI in estrus program resulted in a 20 percent greater pregnancy rate measured after calving and the same proportion of cows pregnant by 150 DIM than the program using all-TAI after Double-Ovsynch and a longer VWP. 

The greater pregnancy rate was observed even though conception risk (i.e., conception rate) at first service was about eight percentage points lower for the targeted program. Basically, the shorter VWP and the good estrus detection efficiency for the targeted program helped compensate for the lower fertility to first service. 

These results were replicated almost exactly in another recent experiment from our group that had a similar TRM program but used an automated estrus detection system with neck-attached sensors. 

However, this experiment also reminded us of the importance of achieving good fertility for inseminations in estrus. For this trial, where we observed lower fertility for AIE services due to herd management conditions and climatic limitations (the experiment was done at a dairy in Mexico where heat stress is a bigger problem), there were no differences between treatments for the percentage of cows pregnant in mid-lactation, but it was harder for the targeted predominant AI in estrus program to catch up with the all-TAI program with longer VWP. 

TAKEAWAYS

Taken together, data from our experiments suggests that TRM strategies that use AEA during the VWP to prioritize insemination of cows in estrus and target use of TAI might be reasonable when pregnancy rate after calving and percentage of cows pregnant by mid-lactation are the most relevant outcomes.

Conversely, TRM programs that prioritize AIE might not be ideal for herds that prefer to or need to maximize first service P/AI.

However, this approach may be appealing for farms that need or prefer a more hands-off management system to minimize labor needs and the number of treatments applied. From a practical perspective, the TRM programs based on AEA during the VWP can help maximize AIE while targeting TAI on cows that otherwise would have a delayed first service. This approach also provides a better justification for synchronization of ovulation for TAI which might be relevant for some herds.

Critical to the success of this type of program is implementation of efficient and accurate estrus detection programs combined with systematic and timely use of synchronization of ovulation. This can be easily accomplished in farms that use automated estrus detection systems during the VWP because AEA can be transferred to the dairy herd management software to assign cows to TRM programs.

Julio Giordano, Ana Laplacette, and Clara Rial collaborated on this research through the Dairy Cattle Biology and Management Laboratory at Cornell University. Visit the laboratory’s website.

This article appeared in PRO-DAIRY's The Manager in November 2024. To learn more about Cornell CALS PRO-DAIRY, visit PRO-DAIRY.