Prolapsed vent (also known as prolapsed oviduct, pickout, cloacal prolapse or blowout) is a common condition in laying hens. During the process of laying an egg, the lower part of a hen’s reproductive tract is temporarily turned inside out, allowing the hen to lay a clean egg, but it sometimes it does not retract again after the egg has been laid. This is called prolapse. It may be resolved if attended to right away. If other hens notice the prolapse first, they may pick at the prolapsed vent which can cause severe damage to the hen. The other hens are attracted to the moist glistening texture of the soft tissue and will start picking at it, causing blood loss, and potentially removal of the cloaca, oviduct, parts of the small intestines, leaving a gaping hole where the vent used to be. Observation is key to preventing cannibalism and pecking behavior. There is no cure for prolapse, so the best method of control is prevention.
WHAT CAUSES PROLAPSE?
There are multiple factors that can contribute to prolapse, most of which are caused by incorrect pre-lay management or nutritional changes prior to the start of egg production. Prolapse can be related to poor skeletal development during rearing, even if the bodyweight during production is at target, if their pelvic girdle is not well developed during the rearing stage. Overweight birds are also more susceptible to prolapse because of muscle weakness and a tendency to lay larger eggs. Too much fat around reproductive organs increases the risk of prolapse. A buildup of fat around the chicken’s abdominal region can narrow the egg passage, potentially resulting in the chicken straining to push the egg out, causing prolapse. Prolapse can also occur if the hen is too young and underdeveloped to be laying eggs.
Unbalanced feed rations can also increase the chance of prolapse. Calcium deficiency in the diet can cause challenges with eggshell formation and can also lead to low muscle tone. Weak muscles can make it harder to retract the oviduct back into the body, which increases the time that the oviduct is exposed. Soft shell eggs can cause the hen to strain hard which also increases likelihood of prolapse. Large eggs, like double-yolkers, can cause the hen to strain too hard, pushing out more inner lining than usual. If a hen is regularly laying large eggs and straining, the cloacal muscles can become stretched, especially with age. Prolapse is more common during peak production periods and periods of peak egg mass as a result of the large demand placed on birds’ metabolism during these times. With prolapse, the death of the chicken is often due to the trauma from other birds pecking the everted oviduct. If there is high light intensity in the barn, this increases the chance of other birds noticing and being attracted to the exposed tissue and start pecking, which leads to the vicious habit of cannibalism which can quickly spread among the flock. Cannibalism can be managed. However, if left to get out of hand it can be very costly and difficult to eliminate.
HOW DO YOU IDENTIFY A PROLAPSED VENT?
The first signs of a prolapse are blood-streaked eggs. The discovery of blood-streaked eggs should prompt investigation to find affected birds. Implement management techniques to reduce the impact of this condition. A prolapsed oviduct is noticeable as it looks like their insides are falling out of their vent and you may also find blood and feces on their feathers around the vent. If the bird has already been picked at by other birds, tissue may be missing, leaving a bloody gaping hole. If the bird has a blowout or it has already been pecked and further injured by other birds, you will be able to spot the hen by her behavior. She will be in noticeable pain and hesitant to move around. She will probably be a bit skittish and want to avoid contact because of the sensitivity and pain. This shows the importance of regular observation to detect issues and react before it becomes serious.
CAN YOU TREAT PROLAPSE?
There is no effective treatment for prolapsed vent. If you find a bird with prolapsed vent, you must take immediate action to remove and isolate it. You may spray the affected area with a medicated spray such as Oxytetravet to aid recovery and keep her in isolation until she improves. The oviduct may eventually retract, but unfortunately the hen will be increasingly likely to suffer from prolapse again in the future. In studies done by Jesse Lyons, an extension poultry specialist at the University of Missouri, birds who experienced prolapse often have a reduction in egg production. It is possible to try remedy a prolapsed vent by pushing it back in yourself by hand, but in a commercial application that is probably not a viable option with the potential for recurring prolapse and laying fewer eggs. If a bird with a prolapse is not removed in time and other birds have picked at the vent causing extreme prolapse and severe damage, the bird may die from hemorrhage and shock, or need to be euthanized.
There are other steps that can be taken once a prolapse has been discovered to reduce further issues. These include supplementing drinking water with Vitamin C at 1g/l water in the morning. It is important if experiencing a prolapse issue to reduce light intensity in the barn to a maximum of 40 lux in open houses and 20-30 lux in environmentally controlled houses. Do not exceed 16 hours of light duration, even under 15 hours is better. Also, if birds are not at the required bodyweight at the typical age for photo-stimulation, it is important to delay photo-stimulation until uniformity is better and birds are at the requited weight. Make sure nest boxes are dark as chickens not only prefer laying in dark comfortable spaces, but other birds are also less likely to see and peck at the exposed prolapsed vent if a bird were to experience one.
As there is no effective treatment, the best way to prevent prolapse from occurring is careful and attentive management. Likewise, effective management and swift response is the best course of action if prolapse occurs as it will minimize the effects of further issues that may arise, such as cannibalism. Key aspects to manage pullets correctly are nutrition and light management. It is important in the growing phase to have good growth and uniformity. It is then that the correct nutrition is needed to produce good quality eggs, as well as have the required skeletal and muscle development to handle laying. Balanced feed ratios help sustain egg production and maintain body weights at the recommended levels. If the flock is laying a lot of double-yolked eggs then gently restrict feed intake. Nest boxes need to be well managed too. They need to be dark enough that the hens will be less likely to notice prolapsed vents and managed so that hens are not able to stay in the boxes longer than necessary. There needs to be regular monitoring of flocks to keep an eye on bird behavior and effective management practices.
Photo-stimulation should only occur when the birds reach the required weight and age determined by the breeder. If pullets come into production too early, they will be more susceptible to prolapse, as well as the potential to lay smaller eggs throughout the production cycle. It also may cause health issues across the flock. When approaching the age of planned light stimulation, assess uniformity, and if the flock has a uniformity under 70% delay light stimulation to allow the less developed birds to mature. If underdeveloped birds are given light stimulation too early it increases the risk of prolapse and peritonitis, reduced hatching eggs, a poorer peak and persistency of lay and a more difficult to manage flock. It is important that the light intensity is at the breeder’s recommended level.
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Fulton, R. M. (2017). Causes of Normal Mortality in Commercial Egg-Laying Chickens. Avian Diseases, 61(3), 289–295. https://www.jstor.org/stable/26432133
Prolapse Vent in Chickens: Causes & Treatment. *Graphic Photos**