Abstract
In most of the artificial raising operations, the separation of dairy calves from their dams immediately after birth and reared under a variety of housing and feeding systems, expose them to different environmental challenges. The objective of this review article was to describe how environmental changes and challenges influence the health and behavior of young calves. Natural behavior, health, and welfare of the calves may be affected when they are reared indoors apart from their dams with another mate. Fresh perspectives on calf nourishment strategies (e.g., intensified vs. conventional milk feeding, and forage feeding) and housing (group or pair vs. individual) have been developed to assimilate the natural environment of calves. In recent years, based on scientific evidence a positive relationship between early-life calf health and later performance of dairy heifers has been indicated. Chronic exposure to stressors may lead to chronic inflammation, resulting in increased infectious disease and suppressed animal performance. Therefore, an effective diagnostic tool for the identification and prediction of the health status and welfare of calves would be to monitor the behavior of calves regularly on the farm. The main factors affecting the behavior of calves and their subsequent productivity are, nutrition and feeding programs, ambient temperatures, incidences of diseases as well as housing systems. Genetics can affect calf response to environmental alterations. In general, it alleviates stress and improves herd profitability and sustainability for producers and farmers by understanding the calves' behavior in response to environmental challenges.