ASSISTED REPRODUCTION TECHNOLOGIES

Assisted reproduction technologies are a crucial strategy for addressing delayed ovulation in cattle, particularly in increasing the effectiveness of AI and pregnancy success rates [202]. It is important to note that these technologies are intended to complement, rather than replace, optimal nutritional, environmental, and hormonal management practices. Accurate timing of insemination is key, as delayed ovulation can lead to a lack of synchrony between mature oocytes and fertilizing sperm [203]. Understanding follicular dynamics, estrus behavior, and the hormonal profile of each individual cow allows for optimal insemination timing, thus increasing the chance of fertilization [204].

In cows affected by delayed ovulation, conception rates following spontaneous AI-based solely on visual estrus detection are generally lower compared to hormonally synchronized programs, due to mistimed insemination relative to the delayed LH surge and ovulation [202]. In contrast, fixed-time artificial insemination (FTAI) protocols have been shown to improve conception rates in these cows by standardizing ovulation timing and reducing the risk of sperm–oocyte asynchrony. Several studies report higher or more consistent pregnancy rates with FTAI compared to spontaneous AI in herds with a high prevalence of ovulatory disorders, particularly under conditions of poor estrus expression or intensive management systems [204].

FTAI is a practical application of assisted reproductive technology to address individual differences in ovulation timing [205]. This method utilizes hormonal protocols, such as Ovsynch or Double Ovsynch, to synchronize oocyte release with insemination at a predetermined time without waiting for natural signs of estrus [206]. FTAI is most effective when integrated with ongoing herd level management, including optimal nutrition, metabolic monitoring, and heat stress mitigation. This approach is particularly useful in cows with delayed ovulation because it reduces reliance on manual estrus detection, which is prone to error and behavioral variability [6]. Through FTAI, ovulation can be triggered with a combination of GnRH and prostaglandins, resulting in simultaneous ovulation across the herd, improving overall reproductive efficiency [207].

The choice of semen type is also an important consideration when applying ART in cows with delayed ovulation. Conventional semen generally yields higher conception rates than sex-sorted semen due to its higher sperm concentration and better resilience to suboptimal timing [206]. In delayed ovulation cases, the narrower fertilization window and reduced sperm longevity associated with sex-sorted semen may further compromise pregnancy outcomes if insemination timing is not optimal. Thus, proper semen selection should be considered alongside ART protocols to maximize reproductive outcomes in herds with variable ovulatory responses [202].

Combining assisted reproductive technology with optimized nutritional, environmental, and hormonal management, along with follicular monitoring and hormonal profiling, provides a comprehensive strategy for managing delayed ovulation [208]. Such an integrated approach allows practitioners to select the most appropriate insemination strategy (spontaneous AI versus FTAI) and semen type based on ovulatory status, herd management level, and production goals, thereby improving insemination success and overall reproductive performance in both dairy and beef cattle systems [164].