Compliance in reproductive management
Strategies to identify cows that do not respond to synchronization protocols
Although the fundaments and metrics of reproduction are extremely straightforward, a large number of US dairy herds still struggle to achieve adequate reproductive performance. Recent surveys indicate that national insemination rate (evaluated as the proportion of eligible cows inseminated every 21 days) and conception rate (percentage of cows that become pregnant from all inseminated cows) average 46 and 39%, respectively. As a result, the average pregnancy rate in US dairy herds is 18%, meaning that less than one in five eligible cows become pregnant at every 21-day breeding cycle. Nevertheless, there are a considerable number of dairies with 21-day pregnancy rate above 30%. Among the several factors that distinguish herds in the extreme ends of this distribution, compliance to stated protocols is of crucial importance for reproductive success.
Limited use of natural service and widespread implementation of artificial insemination (AI) require excellent detection of estrus (heat). Because daily morning and afternoon visual observation is time consuming, numerous alternate methods are available to aid estrus detection such as heat detection patches, tail chalk/paint, and automated activity monitors. Independently of the method, compliance with daily estrus detection is paramount for reproductive success. Inadequate estrus detection rate leads to missed breeding opportunities and delays pregnancy. Simulations performed by researchers at the University of Florida and the Ohio State University estimate a decline of 6 percentage points in 21-day pregnancy rate and an increase of approximately 40 days on herd’s median days open if estrus detection efficiency drops from 60 to 40%. Estrus detection inaccuracy also plays a major role in reproductive performance as insemination of cows that are not in heat rarely results in conception. Improving estrus detection efficiency and accuracy expedites pregnancy and reduces culling of open cows at the end of lactation; thus, reducing replacement expenses and improving overall profitability of the dairy.
The advent of protocols for synchronization of ovulation and timed AI has allowed dairymen to systematically inseminate cows without the need for estrus detection, which narrows the interval to first insemination after calving and controls the inter-AI interval for non-pregnant cows. Most US dairy herds that use timed AI do so concurrently with estrus detection, as studies have demonstrated economic benefits from the combination of the two strategies over timed AI only ranging from $1 to $32 (US dollars) per cow per year. Not surprisingly, compliance with estrus detection remains a critical factor in herds that use timed AI. If daily observation is inaccurate and pregnancy per AI (commonly referred to as conception rate) for cows inseminated in heat becomes limiting, implementing estrus detection results in losses between $8 and $15 (US dollars) per cow per year compared with the exclusive use of timed AI. Similar to estrus detection, compliance with stated synchronization protocols is extremely important for the success of timed AI programs. For instance, failure to regress a functional corpus luteum in cows that do not receive the injection of prostaglandin F2α is expected to reduce pregnancy per AI below 3%. In the same simulation mentioned above, enhancing compliance with synchronization protocols from 85 to 95% (i.e. proportions represent the percentage of injections cows received correctly) increased average 21-day pregnancy rate by 5 percentage points, shortened median days open by 42 days, and reduced replacement costs associated with culling of non-pregnant cows by $93 (US dollars) per cow per year.
One layer of compliance to timed AI protocols that is not controlled by the dairy producer relates to cows’ ability to respond to hormonal treatments. For instance, only 70 to 85% of cows subjected to timed AI successfully regress their corpora lutea and ovulate shortly after insemination. Because non-responders are less likely to become pregnant compared with herdmates that respond to each injection of the synchronization protocol, identifying such cows would allow producers to make better breeding decisions and apply early resynchronization to animals at small risk of becoming pregnant. Although university research has demonstrated that progesterone concentrations in blood can be used to assess response to the timed AI program, cow side tests are required so that progesterone information can be used to assist during routine procedures. Preliminary results from the University of Minnesota (Omontese et al., 2017) abstract accepted for publication at the American Dairy Science Association annual meeting) indicate that commercially available milk progesterone tests provide relevant information about the likelihood of pregnancy following timed AI. Among other results, pregnancy per AI is smaller for cows with low progesterone concentrations at the prostaglandin F2α injection, high milk progesterone at AI, and low progesterone concentrations 7 days after AI. Accordingly, cows with adverse progesterone profile could be diverged to a resynchronization program either before or shortly after previous insemination. Further developments in this area, such as incorporation of milk progesterone measurements into parlor equipment, are expected to improve predictive values and streamline the use of progesterone information for routine decision making in commercial dairies.