From farm management to bacteriophage therapy: strategies to reduce antibiotic use in animal agriculture

To reduce the use of antibiotics in animal agriculture, a number of effective or commercially viable alternatives have been implemented by food animal producers or are under development. Perhaps the most well-established strategies are flock and herd management practices to mitigate disease introduction and spread, and, subsequently, reduce the need for antibiotic use. While vaccines in food animal production have been used to prevent both bacterial and viral diseases, but historically, most vaccines have targeted viral diseases. Though vaccines against viral diseases can help reduce the need for antibiotic use by controlling the spread of secondary bacterial infections, more recent vaccines under development specifically target bacteria. New developments in selecting and potentially tailoring bacteriophages provide a promising avenue for controlling pathogenic bacteria without the need for traditional small-molecule antibiotics. In this article we discuss these established and emerging strategies, which are anticipated to reduce the reliance on antibiotics in food animal production and should reduce the prevalence and transmission to humans of antimicrobial resistant bacteria from these systems.

Hypoglycemia spiking mortality syndrome in broilers with rickets and a subsequent investigation of feed restriction as a contributing factor

Several cases of elevated mortality with neurologic signs in 14-to-16-day-old broilers were presented to the Poultry Diagnostic and Research Center from one local integrated company. Suspected of "spiking mortality" associated with hypoglycemia, blood glucose levels were <150 mg/dl overall, with several birds with blood glucose levels as low as 30 mg/dl. Tissues, submitted for histopathology, revealed rickets in 50% of the birds. Virus isolation and serology for reovirus and infectious bursal disease virus were negative. After evaluation of these cases, a brief investigation was conducted to determine the effects of feed restriction on the induction of rickets and resulting hypoglycemia. One-hundred 1-day-old broilers were randomly assigned to three treatment groups of: 1) ad libitum feed, 2) 25% restriction, and 3) 50% restriction. Restriction began on the fifth day of age and continued to 21 days of age. Samples collected during the course of the study included whole blood for blood glucose measurements and proximal tibiotarsus for histopathologic examination for rickets. We were unable to reproduce the clinical signs of spiking mortality, neurologic changes, or hypoglycemia experimentally. Histopathology of the growth plates of the proximal tibiotarsus did indicate mild changes consistent with rickets, but the changes were not significant between treatment groups.

Increased numbers of duodenal mucosal mast cells in turkeys inoculated with hemorrhagic enteritis virus

The relation between average duodenal mast cell count, duodenal mucosal mast cell numbers, duodenal connective tissue mast cell numbers, circulating basophil numbers, heterophil-to-lymphocyte ratio, and lesion score were studied to gain an understanding of the events that may lead to intestinal lesion formation associated with hemorrhagic enteritis virus (HEV) infection. Changes in vascular permeability in the duodenum in birds inoculated with HEV were examined, using colloidal carbon and ferritin as vascular markers. Turkeys inoculated with HEV had significantly (P less than 0.05) higher duodenal mast cell counts than did noninfected controls. Birds inoculated with HEV had significantly (P less than 0.05) more mucosal mast cells than did phosphate-buffered saline solution-inoculated birds. Connective tissue mast cell and basophil numbers were unaffected by viral inoculation. Thermal stress did not have significant effect on lesion severity, but did increase number of birds that developed the characteristic intestinal lesions. The heterophil-to-lymphocyte ratio was significantly (P less than 0.05) higher in HEV-inoculated birds, compared with phosphate-buffered saline solution-inoculated controls. Increase in vascular permeability was only detected in HEV-inoculated birds with intestinal lesions. Results indicate that mast cells, and the vasoactive mediators contained within mast cells, may be important in the early manifestation of HEV infection. They also provide a possible mechanism through which biochemical and physiologic changes characteristic of HEV infection can occur.