Fatty Liver Syndrome in laying hens
What problems can develop in hen livers?
The egg yolk and whites are predominantly comprised of lipoproteins and proteins. The liver is the main site of fat metabolism in the hen. Fatty liver syndrome (FLS) is characterised by increased lipid accumulation in the liver tissues and is associated with decreased egg production. It occurs more commonly in aged hens, but is also an issue in overweight hens and in hotter temperatures. The liver becomes enlarged and pale due to increased fat infiltration. It is more prone to rupture, resulting in a large bleed into the liver capsule (Fatty Liver Haemorrhagic Syndrome (FLHS)).
How can I detect hens with liver damage?
With FLS, birds can become pale in their wattles and combs and egg production can decrease. With FLHS, mortality can occur due to the volume of blood loss. The drop in egg production occurs due to the liver function being impaired by the fat accumulation. This impacts on fat, carbohydrate, protein, vitamin and mineral metabolism but also specifically due to the role the liver has in metabolising Vitamin D3 to 25-OH VitD3, which is one of the steps needed for Vitamin D3 to become active.
What causes fatty liver syndrome?
Overweight birds, high energy rations, limited exercise, heat stress, mycotoxins, onset of lay and hen aging can all contribute to FLS. The tendency towards FLS can be reduced by free ranging activity. If hens become overweight, supplementation with vitamins complexes and 25-OHVitD3 can help. Insoluble fibre can also help fill birds like whole wheat or some raw vegetable matter but any weight loss should be gradual and closely monitored.
How can you prevent FLS?
Ideally you should monitor the body condition scores of birds closely during housing to prevent FLS, for example under an Avian Influenza housing order. It is easier to prevent illness than it is to treat it.
References
BAR, A., STRIEM, S., ROSENBERG, J. and HURWITZ, S. (1988) Egg shell quality and cholecalciferol metabolism in aged laying hens. Journal of Nutrition 118, 1018–1023.
CHEN, C., TURNER, B., APPLEGATE, T.J., LITTA, G. and KIM, W.K. (2020) Role of long-term supplementation of 25-hydroxyvitamin D3 on laying hen bone 3-dimensional structural development. Poultry Science 99, 5771–5782.
