Fatty liver syndrome (FLS) is a frequently occurring condition in laying hens, especially in white-egg layers and more particularly during the warm season.
Fatty Liver: Causes, Symptoms, and Treatment
The nutritional needs of laying hens vary at each stage of life, so the feed consumed and weight gain are managed based on their growth stage. The control of fat synthesis and degradation programs (fat metabolism) in the bird’s body is influenced by external factors such as diet and environment, as well as a complex of molecules and an unknown internal mechanism.
During the peak production period, laying hens require a high-energy diet. The birds store extra fat in various areas of their body, including the abdominal region, under the skin, around the intestines, near the heart, ovaries, oviduct, and notably in the liver. As fat accumulates in the liver, its tissue softens and becomes vulnerable, leading to fatty liver in the bird.
Fatty liver syndrome is a disorder of fat metabolism that typically occurs in laying hens raised in cages, particularly during the peak period of laying eggs. This syndrome is the greatest health risk to these hens, especially during longer production cycles. In wild animals, fat accumulation in the liver serves as a physiological adaptation to meet energy in specific conditions such as migration and hibernation.
Clinical Signs
Wet droppings or changes in manure consistency are often observed. Mortality increases and at post-mortem excessive abdominal fat is found, the liver appears enlarged and with soft and friable texture, showing changes in color, turning to yellowish due to excess fat storage. When fatty liver syndrome occurs in the herd, in most cases the egg production rate is around 70-85% and it becomes difficult to reach the peak of egg laying. The outbreak of disease in the herd leads to lose their appetite, their mobility is reduced.
The clinical symptoms of this syndrome in laying hens include reduced performance and egg production, weakening of the egg shell, shortening of peak production or failure to reach peak production, increased water consumption, diarrhea, reduced feed efficiency, edema, and visible signs such as swelling of the face, belly, and sudden death of the bird. In normal conditions, losses in breeding farms of laying hens are typically not more than 6%, but in conditions of fatty liver syndrome, the percentage of losses can exceed 20%.
During the necropsy of infected birds, we observe weight gain of liver, bleeding, and the deposition of a large amount of fat in the liver, abdominal area, subcutaneous tissue, intestines, muscles of around the heart, and stomach. Additionally, fat deposits in the liver can lead to blockage of capillaries, pallor, and liver failure. Therefore, fat deposits increased in the ducts, chickens experience significant pressure during production, which can cause to rupture and internal bleeding of the liver.
Managing, improving daily production, and creating a suitable environment are the most important measures to prevent fatty liver disease in laying hens. In general, providing a standard system and, hygienic environment, maintaining appropriate temperature and humidity, regular disinfection, optimal ventilation, and avoiding the accumulation of toxic gases in poultry breeding halls are the most important preventive measures for fatty liver.
Fatty liver disease can be prevented by carefully monitoring and paying attention to ensuring good feed quality, preventing the consumption of toxin.
Mycotoxins trichothecene and fumonisin affect oxidative stress and lipid peroxidation. These toxins may reduce the function of liver microsomes by inducing the process of lipid peroxidation. They also inhibit the function of the xenobiotic system (cytochrome P450), leading to a decrease in the amount and activity of biological defense antioxidants, particularly the reduction of redux glutathione systems. Depending on the degree of oxidative stress in the liver, these toxins can induce fat liver. Previous research has shown that trichothecene mycotoxins increase the process of lipid peroxidation.
Treatment of Fatty Liver in Laying Hens
Laying hens have varying nutritional requirements at the different life stages. Therefore poultry growth control by amount of feed consumed based. Furthermore, implementing appropriate nutritional and management strategies can help minimize the adverse effects of fatty liver.
Nutritional Method of Treating Fatty Liver in Laying Hens
The most important nutritional method to reduce the complications of fatty liver is maintaining a balanced ratio of protein to energy. In fact, the feed should contain less than 6% energy and higher fiber. During the production period, frequent measurement of body weight and feed energy consumption is necessary. Moreover, balanced amino acid nutrition is crucial for preventing fatty liver because amino acids are essential for the transfer of fatty acids to adipose tissue.
Feed rations should be formulated based on the species and production rate of the bird in order to control the ratio of energy to production within a reasonable range. The ratio of energy to protein in the diet of laying hens varies according to the temperature and the laying percentage. Decreasing the amount of energy in the feed ration below the bird’s needs causes to fatty liver due to increased stress on the liver. Furthermore, providing the required energy from fat to form the yolk is much easier than carbohydrates.
Nutritional Dietary Supplements to Reduce the Incidence of Fatty Liver Syndrome in Laying Hens
In addition to nutritional methods with proper management, the negative effects of fatty liver can be minimized in the herd by improving the quality and balance of the ration, adjusting the size of the screen, the particle size of the feed, providing the right space, adjusting temperature, and reducing stress in the herd by decreasing extra activities of workers, minimizing equipment noise and vibrations in the hall, and the type of stresses in the chickens.
In general, the prevalence of fatty liver in laying hen flocks is high in summer. The use of feed additives, such as vitamins (E, B, A, C), minerals (selenium, etc.), amino acids (choline, methionine, betaine), and bile acids (aimed at improving the metabolism of fatty acids), can prevent fatty liver syndrome or reduce its negative consequences. Additives that improve the digestive system, such as probiotics, prebiotics, phytogenics, and acidifiers. In addition, they can reduce the effects of inflammation, strengthen the effects of antioxidants, improve digestion and absorption of nutrients, prevent the presence of toxins, and finally improve barriers to prevent liver diseases.
