Among all animals present on a dairy farm, the highest morbidity and mortality rates generally occur in baby calves prior to weaning. The National Animal Health Monitoring System (NAHMS) estimated preweaning mortality of U.S. dairy calves to be 10.8%, and the average age at first calving was reported to be 25.8 months. Diarrhea accounted for 52.2% of mortality, followed by respiratory problems (21.3%), trauma (2.4%), joint and navel problems (2.2%), and other or unknown causes (21.9%).1 Many diseases of newborn calves can be controlled by well-designed health management programs that define the care and housing of the dam during the periparturient period, standard operating procedures for the calving process, and the application of proper preventive measures (including sound nutritional programs) for the newborn calf.
Simple exposure to infectious agents is not sufficient cause for the development of diseases in calves. In calf rearing, the difference between health and disease is very often just a slight tip of a delicate balance that weighs calf and environmental factors with the bacterial, viral, or parasitic agents to which the calf will be exposed. The infectious agents that are capable of causing scours, pneumonia, or septicemia in young calves are ubiquitous. Calves will inevitably be exposed, and several may become infected, but only a few should get a disease if the relevant risk factors are minimized and the sources of infection are diluted or bypassed.1 The three most important disease problems in the young calf are septicemia, diarrhea, and pneumonia. Even though the immune system of a calf is functional at birth, it is less responsive than that of an adult cow and is naive and easily overwhelmed by the bacteria, viruses, or parasites in the environment. For dairy calves, inappropriate volume, concentration, fat or protein content, mixing, or feeding temperature of milk or milk replacer can compromise the immunity of the calf.1 Calves are given colostrum to protect them with passive immunity until their own immunity takes over. If calves are not staying with their mothers, as is in the case of dairy calves, then they should be fed colostrum from their mother or from another suitable dam. Vaccinations and deworming can also be used to further protect calves from disease, as well as separating them from the group if showing clinical signs of disease.
1Calf Diseases and Prevention. (n.d.). Retrieved February 25, 2017, from http://articles.extension.org/pages/15695/calf-diseases-and-prevention