UNDERSTANDING PUBERTY AND POSTPARTUM ANESTRUS

Managerial and economic efficiencies of cattle reproduction systems that are seasonal in nature are most likely to benefit from having a compact calving season. Effective replacement heifer development is a critical segment of the integrated management program in an efficient beef cow production system. The replacement heifer represents the future profitability and genetic improvement of the cow herd. The main objective should be to raise an adequate number of heifers to reach puberty and cycle regularly at the start of the breeding season (Corah and Hixon, 1992). In order to achieve this goal, heifers must reach puberty before 12 to 13 months of age, conceive at 14 to 15 months of age, and calve at approximately 2 years of age (Schillo et al., 1992). Researchers at Montana State University concluded that heifers that conceived the earliest immediately indicated their greater productive efficiency and lifetime production potential (Paterson et al., 1987). Beef heifers that calve by 2 years of age have a greater lifetime production potential than heifers that calve at older ages (Patterson et al., 1992).The onset of puberty is the result of a series of complex developmental events that occur within the reproductive endocrine axis. In general, puberty is the process of acquiring reproductive competence. Puberty in heifers can be characterized in several ways including age at first estrus (heat), age at first ovulation, and or age at which a female can support pregnancy without any difficulty (Senger, 1999). Regardless of the criteria used to define puberty, there are several major physiological, environmental, and managerial factors that can advance or delay the age to puberty. A more thorough understanding of the physiology of puberty and factors affecting the timing of the onset of puberty in the heifer will lead to development of new and better management strategies for reducing the age to reach puberty in the heifer and enhancing the reproductive efficiency and profitability of the farm.