Avoiding Kidney Damage in Laying Hens

Kidney damage may not show symptoms until it is too late.

Avoiding Kidney Damage in Laying Hens

Reading Time: 5 minutes

Kidney or renal failure is currently one of the leading causes of death in commercial laying hens. Kidney disease in laying flocks has been on the increase for at least 30 years. Most backyard poultry keepers rarely give such damage and disease in poultry much thought. Home flocks do not generally experience as many issues with kidney health and malfunction as commercial flocks. Nonetheless, the possibility is still present. There are several simple things a flock owner can do to maintain optimum kidney health in their birds. Hens with healthy kidneys will have a much greater chance of staying productive and healthy for many more years than those raised with conditions that contribute to kidney problems. 

Kidney malfunction in poultry may show very few signs until the sudden and final stages when it is often too late to remedy. Kidney failure often exhibits a sudden onset, and a seemingly healthy, productive hen may succumb rapidly, often within 24 to 72 hours. The most common signs of kidney malfunction are pale combs, dehydration, and depression. Other signs may be loss and atrophy of breast and leg muscle. Unfortunately, these signs may not appear until the final stages of the disease. 

About avian kidneys: 

A bird’s kidneys are housed in protective pockets, in the upper regions of the pelvic bones, on either side of the spine. Each kidney has three major divisions, and each division contains several smaller lobes. Like in mammals, the purpose of the kidneys is to filter wastes and toxins from the blood. Healthy kidneys are an integral part of maintaining the proper chemical composition of the blood and other body fluids. They also help regulate blood volume, produce hormones that regulate blood pressure, and produce red blood cells. 

A hen can look healthy and still be laying regularly with only one-third of her kidneys functioning.  For this reason, we may not recognize progressive kidney damage in birds until it is too late.

A hen can look healthy and still be laying regularly with only one-third of her kidneys functioning.  For this reason, we may not recognize progressive kidney damage in birds until it is too late. Two of the three lobes of each kidney can be impaired, and the bird will still act and function normally. While the damaged lobes of the kidneys will atrophy and shrink, the working lobes will increase in size as they take on the other sections’ work. If the causative problem is not identified and remedied, these lobes will also succumb to the same issues that damaged the other lobes, and the bird’s death will occur. 

What can cause kidney damage in poultry?  

The most common causes of kidney disease in poultry stem from dietary issues. Other, much-less-frequent causes of kidney damage can be certain strains of avian bronchitis, some disinfectants and insecticides, and overuse of some antibiotics. However, as dietary and mineral-intake issues are the most common causes of kidney damage in fowl, I will concentrate on these.  

The most commonly found kidney disease in pullets and laying hens is gout or urolithiasis. This is an often-lethal build-up of calcium and other crystalline mineral deposits in the kidneys and ureters of the bird. Gout can result from excessive dietary calcium that does not have adequate phosphate balance, too much calcium when the bird was still young, or dehydration from lack of water. Sometimes known as visceral gout in poultry, a chalky layer of calciferous compounds eventually forms on the surfaces of the abdominal organs and the heart sac and may be found during post-mortem examination. Fortunately, common calcium supplements fed to flocks, such as oyster shell, contain adequate phosphorous in the natural state. 

Young poultry should not be fed a layer ration until they are ready to lay eggs.

A balance of both calcium and phosphorous (phosphate) must be present in poultry and other animal diets. While calcium is an essential dietary mineral, especially in egg production, corresponding phosphorous levels must also be present. Calcium and phosphorous are very closely related in the diet and work in conjunction with each other. One important feature of this balance is proper kidney function. Phosphorous acts as a buffer and neutralizer in the urine. Without it, damaging mineral deposits will build in the kidneys and urinary tract, resulting in renal failure and death. Feed manufacturers try to make sure adequate levels of phosphorous are included in processed feed. Laying rations may contain 3% or more dietary calcium, while necessary phosphorous in prepared rations is generally at a level of 0.4 to 0.5%.  

In commercial flocks, prescribed amounts of ammonium chloride or ammonium sulfate are sometimes added to the feeds to help acidify the urine in the birds and break down crystalline deposits if gout does develop. However, if a poultry owner can avoid getting into these problems first, it is so much better. 

Ensuring good kidney health in your birds  

Here are a few simple things you can do to help your birds maintain healthy kidneys: 

  1. Maintain an adequate supply of fresh drinking water at all times. Whether you are dealing with chicks three days old or hens three years old, a constant supply of fresh drinking water is one of the most important things you can do to ensure good renal or kidney health in your flock. Adequate fluid intake will help ensure excess mineral levels are flushed from the system and kidneys. We often think of hot weather as a critical time for dehydration risk. However, if you live in an area where drinking water freezes in the winter, your birds are at serious risk of developing kidney damage during this time. Make an extra effort to ensure they have as much fresh drinking water as possible during the cold, freezing winter months. Their metabolisms require adequate hydration in all types of weather to function correctly.  
  1. Do not raise baby chickens, young pullets, or other young poultry on laying mash or laying feeds. Growing rations usually contain about 1% calcium, total. Laying rations can contain 2.5% to 4% calcium. The kidneys in young, growing poultry cannot process these high levels of calcium. The high calcium levels will start to build up at a very young age and damage the kidneys. Unfortunately, the damage will be hidden and will generally show up later, often during the final onsets of kidney failure. Once this type of damage starts, it can exacerbate and worsen at an almost exponential rate. Kidneys damaged from excess calcium will not process either calcium or phosphorus correctly. Wastes will not adequately discharge, and the back-up of mineral compounds will start to block working areas of the kidneys and urinary system. Sections of the kidneys will begin to atrophy and die. Eventually, loss of production and early death will result. 

Do not raise young poultry on laying feeds. The kidneys in young, growing poultry cannot process these high levels of calcium. Unfortunately, the damage will be hidden and will generally show up later, often during the final onsets of kidney failure.

  1. Use antibiotics with care. If your birds are sick and need antibiotics, by all means, give them the medicine. Some diseases, including certain strains of avian bronchitis, can leave lasting damage to kidneys and other organs. These are generally treatable with antibiotics. In these cases, it is far better to use the drugs and eradicate the problem. However, if the problem does not remedy after a couple of medication rounds, consult a veterinarian for the next options. 
  1. Use only insecticides tested and manufactured for use on poultry. Some insecticides contain toxins that are harmful to avian kidneys. 
  1. Last but not least, make sure there is a correct calcium-to-phosphorous ratio in your feeds. Commercial rations should already have this balance. If you formulate your own feeds, pay close attention to this. As hens get older, supplemental calcium may be required to maintain shell strength and bone health. Fortunately, most natural sources of calcium also contain phosphorous. When supplemental calcium is supplied, make doubly sure that lots of water can allow their systems to utilize and process the extra minerals properly. 

A little awareness of potential kidney problems and knowing ways to avoid damage will help a poultry owner maintain healthy and productive birds for a much more extended period of time. 

Originally published in the 2021 special issue of Backyard Poultry — A Natural and Sustainable Flock — and regularly vetted for accuracy. 

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