Blood Chemistry Weaning Stress Study

Abstract

Shipping fever complex in the weaning calf is a paramount problem to the beef cattle industry. The highest incidence of disease and death loss is associated with weaning, transportation, handling, and ration adaptation. Most research has concentrated on the bacterial and viral aspects; however, some research has been done on the changes in physiological status of the animal as a result of stress. These changes are related to clinical signs, blood composition alterations, and adrenal gland changes (1). Perhaps the most constant indicator of stress has been the changes in the activity of the adrenal gland. The cortisol activities on the immune system in the weaned and trucked calf may play a major role in the susceptibility and subsequent disease in this calf. This study was conducted to evaluate the effect of weaning stress on 10 blood serum components, hematology, and weight changes. As in the previous study, the most noticeable changes were in the cortisol level and weight change (1). Our general observation on this study and a similar study conducted two years ago is as follows: Animals weaned 4 weeks prior to trucking undergo a stress period lasting 3 to 7 days. Weaning alone stresses these animals for about the same period. Concurrent weaning and trucking increases the stress period to 15-21 days. These conclusions are based upon changes observed in the cortisol, LDM, SGOT, WBC and weight change. The majority of the shipping fever pneumonia occurs in the first 45 days following weaning, caused by the interaction of stresses, viruses, and bacteria (2,3). In this study, we were able to show that the weaning and trucking produced the most stress and failure to gain weight. The higher cortisol the first 7 days and not returning to normal for 15-21 days may suppress the immune system of the calf. An interesting follow-up of this study would be to evaluate the responses to a known antigen in each of these groups.