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Early chick mortality associated with rupture of the yolk sac
1Department of Veterinary Diagnostic Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul 55108.
Insights
Careless chick handling by new sexors caused yolk sac rupture, leading to high early mortality in leghorn chicks. Careful handling resolved the issue, suggesting mechanical injury as the primary cause.
Area of Science:
- Veterinary Medicine
- Poultry Science
- Animal Pathology
Background:
- High mortality rates (up to 3%) observed in young leghorn chicks.
- Clinical signs included abdominal fluid, swollen kidneys, and visceral gout.
- Bacterial causes were ruled out, prompting investigation into other factors.
Purpose of the Study:
- To identify the cause of high early mortality in commercial leghorn chicks.
- To investigate the role of yolk sac rupture in chick mortality.
- To determine if mechanical injury during sexing is a contributing factor.
Main Methods:
- Observational study of field cases with high chick mortality.
- Experimental reproduction of the condition via intraperitoneal yolk injection in day-old chicks.
- Dose-ranging study using 0, 0.5, 1.0, 2.0, and 4.0 ml of egg yolk.
Main Results:
- Yolk sac rupture and associated mortality were linked to new sexors' handling.
- Experimental yolk injection at 4.0 ml caused mortality, swollen kidneys, and abdominal fluid.
- Lesser yolk doses or no injection resulted in significantly lower mortality.
Conclusions:
- Mechanical injury during chick handling, specifically by new sexors, is a likely cause of yolk sac rupture and subsequent mortality.
- Intraperitoneal yolk administration can experimentally induce similar pathological findings.
- Improved handling protocols are crucial for reducing early-stage chick mortality in hatcheries.
Abstract:
Rupture of the yolk sac was identified in leghorn chicks from six placements of a commercial hatchery that had high mortality (up to 3%) during the first 3 days. The abdomens of these chicks were filled with cloudy yellowish fluid; kidneys were swollen, and many chicks also had severe visceral urate deposition (visceral gout). No significant bacterial growth was detected. The hatchery had recently hired new sexors. After the sexors were cautioned to handle the chicks more carefully, the problem abruptly subsided. In an experimental attempt to reproduce the condition, a graded series of doses (0, 0.5, 1.0, 2.0, and 4.0 ml) of egg yolk were injected intraperitoneally into five groups of twenty 1-day-old chicks. Twelve of the 20 chicks that received the 4-ml dose died. They developed swollen, pale kidneys and had cloudy yellow fluid in the abdominal cavity, but no visceral urate deposition. Only six of the remaining 80 chicks that received lesser doses or no yolk died.
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