Infection of the yolk may be accompanied by omphalitis, and may originate prior to incubation, during incubation or after the birth of animals.

Prior to incubation, infection can occur by contamination of the eggshell from the nests, once the egg is laid, or it can occur even earlier: certain infectious agents can affect the reproductive structures of laying animals, including ovary and oviduct, and penetrate the white and yolk.

There are different agents that can cause this infection in breeding birds, which lead to yolk infections in ducklings due to their vertical transmission: these are sulfate-reducing enterobacteria, such as Salmonella, Pseudomonas or Proteus, which have a type III secretion system, a pathogenic weapon of great capacity.

The liver infection caused by these bacteria in breeding birds can be transmitted to their reproductive system due to their anatomical proximity, and from there be transferred to the progeny.

The yolk infection can be visible in 1-day-old ducklings upon arrival at the farm, where the yolk of a greenish color and increased in size can be observed: at that moment it is assumed that there are difficulties for its absorption and that this challenge can affect performance of affected animals and mortality in the first week of life.

The joint action of the infection and the toxins will reduce the growth capacity and slaughter weight, worsen the conversion and increase the mortality in the first week of life.

Usually, the yolk is rapidly absorbed after birth and there are many times when this organ cannot be used as a reference. In most cases in which Salmonella has been isolated from 1-day-old ducklings, it was obtained from the liver or cecum in asymptomatic carrier animals.

Ducks seem to be more resistant than other types of domestic birds, and the systemic presentation of the disease is normally associated with the presence of stressful factors, such as cold temperatures. In these young animals, we can find very characteristic digestive lesions, including hepatitis and typhlitis.

How to reduce the impact of yolk infections on productive parameters?

The prevention plan of vertical transmitted infections should include the assessment breeding ducks to stop the possible bacterial spread. The control of this productive stage is key to offer ducklings of the proper microbiological quality.

Once the agent is identified, the control plan should include the elimination of carrier animals, together with the treatment of the breeders with antibiotics of enterohepatic cycle. In future cycles, the development of an autovaccine can be considered, as well as the routine inclusion of a natural microbicide in feed and periodic monitoring to avoid new infections in adult birds.

Furthermore, it is recommended to administer a microbicidal solution in the drinking water during the first week of life of the animals, to act at intestinal level and promote the reabsorption of the yolk. Products based on the combination of the cimenol ring and citric acid offer a powerful bactericidal activity and are the ideal tool for these cases.

Sources:

• Barrow, P.A.; Lovell, M.A.; Murphy, C. K. and Page, K. (1999). Salmonella infection in a commercial line of ducks; Experimental studies on virulence, intestinal colonization and immune protection. Epidemiol. Infect. (1999), 123, 121–132.
• Riberto, S. et al. (2006). Incidence of Salmonella in Imported Day-Old Ducklings. Brazil, 1998-2003. Brazilian Journal of Poultry Science ISSN 1516-635X Jan – Mar 2006 / v.8 / n.1 / 39 – 43.