The nutrients and antibodies within the yolk sac are absorbed and utilized by the chick. The yolk sac is attached to the navel and via this route infection can enter.
Due to the being full of nutrients, any bacteria which gain entry can develop rapidly and lead to the death of the chick.
Signs
The chicks will become lethargic and die rapidly after hatching with a peak morality within 48 hours. The abdomen is swollen and there is a putrid, yellow swollen sac within the abdomen. The liver is swollen and the navel is often also enlarged due to localized infection. In a batch of chicks with yolk sac infection there is a characteristic putrid smell.
Aetiology
The infection is often related to E coli or pseudomonas bacterial infection. The origin of the infection might be the hatcher or infection via the navel post hatching. Hatchery disinfection, air quality and egg handling all need to be considered. Washing contaminated eggs with poor quality water and allowing bacteria to enter the egg will lead to eggs exploding when handled or in the setter. The environment then becomes infected and normal chicks can rapidly become infected after hatching. In order to control a regular problem a detailed examination of the causes is needed.
Treatment
In many cases there is no treatment as the condition is very rapid. However, in some problems it is worth considering treatment of the flock to prevent infection spreading to other birds. You should contact your vet or one of our team if registered with us to discuss treatment options.