India has the largest population of cattle (192.49 million) and buffaloes (109.85 million) in the world (20th Livestock Census, DAHD, Government of India). Cattle and buffaloes contribute around 51% and 45%, respectively, to the total milk produced in India. Thus, cattle and buffaloes are a major source of income for the farmers and contribute to the economy of India. But the reproductive efficiency of cattle and buffaloes is largely affected by delayed maturity, silent heat, poor estrus detection, repeat breeding, prolonged inter-calving period, and poor conception rate. Estrus detection is poor in cattle and especially in buffaloes because of poor expression of estrus, poor vocalization, absence of homosexual behavior, peak sexual behavior in night, and silent heat due to high environmental temperature.

Estrus detection in animals means the identification of the female animal that is ready to mate with the male for the sex. Estrus cycle in cattle and buffaloes is around 21 days but the period of heat, when the animal is ready to mate, lasts for only 6-30 hours. Inefficient estrus detection in cattle and buffaloes results in financial loss to the farmers and reduces the fertility status of the herd. Due to this, timely Artificial Insemination (AI) in animals is missed leading to failed conception. Estrus detection failure in animals is directly related to the prolonged calving interval, and it directly affects the milk production and income of the farmers. Thus, timely detection of estrus is a challenge in the cattle and buffaloes for the success of the AI and it will help in effective reproductive management of cattle and buffaloes. Estrus may be detected in cattle and buffaloes by conventional and advanced methods.