Investigations into Increased Incidence of Severe Gizzard Erosions and Ulcerations in U.S. Commercial Broilers

During a series of pathology surveys in four production complexes of a U.S. broiler integrator, the technical services veterinarians of an animal health company noted a high incidence of severe gizzard erosions and ulcerations (GEU), prompting further clinical investigation and a battery trial. No growth-promoting antibiotics or ionophore coccidiostats were used during the period of these surveys. All used tribasic copper chloride (TBCC) at ≤120 ppm added copper in broiler rations. Clostridium perfringens was isolated from 83% and 67% of gizzard lesions cultured in two complexes, and cecal C. perfringens most probable number determinations were higher in severely affected than in mildly affected or unaffected birds. Histopathology revealed both acellular koilin fusion defects characteristic of copper toxicity, as well as inflammatory cell infiltrates. Intralesional bacilli suggestive of C. perfringens were noted in 78% of affected flocks examined. Species E Aviadenovirus was isolated from one bird in one complex, and that bird had a single intranuclear inclusion body; no other flocks had Adenoviruses isolated or detected on PCR, nor any inclusion bodies. Other viruses detected were thought to be incidental. A pilot study using feed with supplemental copper from TBCC or copper sulfate and challenge with one of the isolated C. perfringens strains reproduced the lesions. A battery study was conducted with an unchallenged negative control group fed a diet with 16 ppm added copper, a group fed the control diet and orally challenged with 10⁸ organisms of a field strain of C. perfringens at 21 and 22 days, and a group treated with the same diet containing 250 ppm added copper from TBCC and orally challenged with C. perfringens. Birds were necropsied at 23 and 28 days. All challenged groups developed lesions, with those receiving both TBCC and C. perfringens having significantly higher gross and histopathological lesion scores than the unchallenged negative controls. Lesions were qualitatively similar to those in the field and contained suspected C. perfringens bacilli. Because the levels of TBCC used in the commercial birds and in the battery trial generally have been considered safe, and because C. perfringens is usually regarded as a pathogen of the lower GI tract, the possible association of these two agents with GEU is a novel observation and warrants further investigation.