International Journal of Molecular Zoology, 2024, Vol.14, No.6, 305-314 http://animalscipublisher.com/index.php/ijmz 306 2 Biological and Physiological Basis of Reproduction in Water Buffalo 2.1 Reproductive anatomy and physiology Water buffaloes (Bubalus bubalis) are multipurpose livestock known for their milk, meat, and draught power. However, they exhibit low fecundity characterized by delayed puberty, less pronounced estrus signs, and long postpartum anestrus periods (Qg et al., 2020). The reproductive anatomy of buffaloes is similar to that of other bovines, but their physiological characteristics, such as ovarian cyclicity and estrus expression, are often influenced by environmental and management factors (Bm, 2019). The ovarian function during the estrous cycle is crucial for the application of assisted reproductive technologies (ART), which aim to synchronize follicular development and ovulation (Baruselli et al., 2018). 2.2 Seasonal breeding and its implications Buffaloes are seasonal breeders, with reproductive activity peaking during periods of decreasing day length, typically from late summer to early autumn. This seasonality is influenced by both exogenous factors like photoperiod and climate, and endogenous factors such as hormonal regulation (D’Occhio et al., 2020). Seasonal breeding patterns can lead to challenges in maintaining consistent milk production and reproductive efficiency throughout the year. In regions like Nepal, buffaloes show active breeding from July to December, with low reproductive activity from April to June and January to March (Devkota et al., 2022). This seasonality necessitates management strategies to mitigate its impact, such as hormonal treatments to induce estrus and ovulation during the non-breeding season. 2.3 Hormonal regulation of reproduction The hormonal regulation of reproduction in buffaloes involves complex interactions between endogenous hormones and external factors. Melatonin, produced by the pineal gland, plays a significant role in regulating reproductive seasonality by influencing gonadotropin secretion and gonadal function (D’Occhio et al., 2020). The presence of melatonin receptors, such as MT1 and MT2, and their genetic polymorphisms have been associated with variations in reproductive activity (Gunwant et al., 2018). Hormonal protocols, including melatonin implantation and estrus synchronization, have been developed to enhance reproductive performance, particularly during the non-breeding season. These protocols aim to control follicular and luteal functions, allowing for timed artificial insemination and improved conception rates (Baruselli et al., 2018). In summary, the reproductive efficiency of water buffaloes is intricately linked to their biological and physiological characteristics, seasonal breeding patterns, and hormonal regulation. Understanding these factors is essential for optimizing reproductive technologies and improving productivity in buffalo herds. 3 Current Reproductive Technologies in Water Buffalo 3.1 Artificial insemination (AI) Artificial insemination (AI) is a pivotal technology for genetic improvement and controlling the breeding period in water buffalo. However, AI in buffalo is more challenging than in cattle due to irregular estrous cycles, subdued estrous behavior, and reproductive seasonality, which can lead to higher rates of anestrus and embryonic mortality outside the breeding season. Recent advancements in AI protocols focus on controlling the luteal phase with prostaglandins and progesterone, and managing follicle development and ovulation using hormones like GnRH, hCG, eCG, and estradiol. These protocols facilitate fixed-timed AI, eliminating the need for estrous detection and improving reproductive efficiency (Neglia et al., 2020; Coman et al., 2024). 3.2 Estrus synchronization techniques Estrus synchronization (ES) is often used alongside AI to enhance reproductive efficiency in buffalo. The difficulty in detecting estrus in buffaloes can lead to suboptimal timing of AI, reducing reproductive success. Various ES protocols, such as those involving prostaglandin and GnRH, have been developed to improve pregnancy rates. Studies have shown that administering ovulatory hormones like GnRH or hCG at the time of AI can significantly enhance pregnancy rates, making these protocols both effective and cost-efficient for field application (Atabay et al., 2020; Ahmad and Arshad, 2020; Du et al., 2021).
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