Some effects of reduced energy intake on the development of anaplasmosis in Bos indicus cross steers.

Some effects of the plane of nutrition on the development of anaplasmosis in Brahman cross steers were investigated. Batches of 39 and 30 Brahman cross steers, aged approximately 27 months were each divided by stratified randomisation into 4 groups of similar mean PCV and body weight. Two similar experiments, designated A and B were conducted. Groups 1 and 2 were fed a ration of lucerne chaff at the rate of 1 M Cal ME/80 kg live weight/day for 8 weeks aimed to reduce body weight by approximately 5 kg/week. Animals in groups 3 and 4 were fed a ration for the same period aimed to increase body weight by approximately 2 kg/week. Groups 1 and 3 were then inoculated with approximately 10(10) Anaplasma marginale infected erythrocytes and the effects of the subsequent infections during the clinical and recovery phases were examined by measuring humoral antibody response, packed cell volume, parasitaemia and body weight. Groups 2 and 4 were uninfected controls. Anaplasmosis, as measured by three responses, was less severe in the starved animals of group 1. Significant differences in packed cell volume and parasitaemia were detected for short periods between the infected groups 1 and 3. Anaplasmosis caused losses of 6.2% and 5.9% in the mean body weight of group 3 animals in experiments A and B respectively. Most of this loss occurred during the clinical phase of the disease. The disease caused no apparent loss of weight in the infected animals of group 1.