In Bos taurus beef females, acclimation to human handling after weaning actually expedites reproductive development in replacement heifers [8]. Repeated regrouping and repenning showed no sustained detrimental effect on production or immune measurements in steers [17]. Early weaned Brahman-cross steers kept onsite before transportation were more tolerant to transport stress and feed lot entry and had improved feed to gain ratios [15]. In conclusion, managerial factors such as stabulation, animal density, grouping and transportation, through activation of autonomic nervous system response and up-regulation of the hypothalamus-pituitary-adrenal axis, can affect not only animal welfare but also disease susceptibility, productive and reproductive performances. However, the cellular mechanisms through which this happens are not completely elucidated yet.