Abstract
This paper describes the clinicopathologic findings of 13 cases of embryonic (10/13) or neonatal (3/13) mortality in a colony of captive horned guan (Oreophasis derbianus) at Africam Safari Zoo in Puebla, México, from 2002 to 2008.
Five embryos presented with malformations of the yolk sac with entrapment of the right hindlimb (4/5) or both hindlimbs and neck (1/5). One affected embryo had unilateral renal hypoplasia. There were five cases of embryonic malposition, which was considered lethal in four embryos. Histologically all processed lungs (two embryos with yolk sac entrapment and two with malposition) had aspiration of amniotic fluid. Mineralization of yolk sac, kidney, and/or proventriculus was observed in five embryos examined microscopically. Two neonates had necrosuppurative omphalitis with bacteria; one of which also had bacterial myocarditis, bronchopneumonia, and osteomyelitis of the skull. A third neonate had bacterial pneumonia. Pseudomonas aeruginosa was isolated from all neonates.
During 2002 and 2003, when yolk entrapment was observed, eggs were artificially incubated using Humidaire 20 and 21 models at 99.5°F (37.5°C). Humidity was maintained at 45–60% to achieve a 15% weight loss. Eggs were placed on their sides and automatically turned 24 times a day. In subsequent seasons eggs were incubated by domestic turkeys, and viable chicks were obtained. Weight loss during the incubation under the turkeys was determined to be 17.1±2.6% (n=25). Artificial incubation was attempted again in 2006 and 2007, with a Grumbach incubator at 99.0°F (37.2°C) with humidity adjusted to obtain 17% weight loss. A total of 29 embryos were successfully hatched during the study period.
This is the first description of embryonic and neonatal mortality in endangered horned guan. The embryonic malpositions are attributed to inappropriate egg rotation and positioning.1 Rough handling or improper turning can contribute to yolk sac entrapment, which is more common in artificially incubated eggs.2 The mineralization may have been due to inappropriate incubation temperatures, dehydration, or tissue degeneration due to hypoxia associated with malpositions. Yolk sac entrapments were no longer observed in this colony after artificial incubation was changed to incubation using domestic turkeys. The neonatal bacterial infections that were observed were part of two Pseudomonas spp. outbreaks also involving scarlet macaw and golden eagle chicks in the avian nursery unit.
Literature Cited
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2. Rideout, B.A., and C.M. Kuehler. 2000. Pathology of the avian embryo: what veterinarians need to know about pathology as a disease surveillance tool for avian captive propagation programs. Proc. Am. Assoc. Zoo Vet Annu. Meet. Pp. 329–334.