36 Preweaning causes of morbidity and mortality

Abstract

Abstract Prior to weaning, beef calves are susceptible to a variety of traumatic, infectious, parasitic, nutritional, and metabolic diseases. Calves less than three weeks of age are particularly vulnerable to weather-related factors that may induce hypo- or hyperthermia, predation and other forms of physical injury, and metabolic diseases often related to starvation. The most common infectious cause of death in calves less than three weeks of age is diarrhea due to a variety of viral, bacterial, and protozoal infections. The leading cause of death in calves from 3 weeks of age to weaning is pneumonia, although parasitism and nutritional deficiencies are common causes of impaired productivity at that age. Both neonatal calf diarrhea and calf pneumonia can be explained in part by age-related susceptibility due to loss, or failure to acquire, maternal immunity from colostrum. The waning of passively-acquired maternal immunity, in the gut in the case of neonatal calf diarrhea, or systemically in the case of pneumonia, prior to the onset of a strong acquired immunity creates an age-related window of susceptibility for these two important infectious diseases of calves prior to weaning. Most pathogens associated with diarrhea or pneumonia are endemic to most cattle herds. The adult cow herd serves as the reservoir of these agents from one year to the next. Between birth and weaning, pathogens are primarily transmitted between calves by direct contact or through contaminated environmental surfaces. The incidence of both neonatal calf diarrhea and calf pneumonia are affected by population dynamics that create opportunities for effective contacts. The system of management either creates or averts the relative opportunities for all forms of calf-hood diseases, and the design of beef cattle production systems that favor disease prevention remains an important scientific endeavor.