Cannibalism in Chickens

Definition

Act of one bird consuming a part of the body of another individual of the same species. The term is also used for vicious pecking of a body part leading to injury/death. Birds are especially inclined to peck bright red areas like the cloaca, comb (picture 1), and/or bleeding wounds, but other areas like toes can also be the target of cannibalism (picture 2). 

There are no firm guidelines for preventing cannibalistic behavior. However, several factors increase the risk of cannibalism. As such, they should be treated as predisposing factors; their presence does not necessarily indicate that cannibalism will occur. In fact, in poultry production, many of the predisposing factors co-occur without any resulting cannibalism. On the other hand, cannibalism may be observed in operations with few predisposing factors, in which it seems unlikely that it would occur.

 
Picture 1. Cannibalism in broiler chickens. Photo credit: Dr. I. Rojas.

 
Picture 2. Dermatitis in young broiler chickens associated with cannibalism. Photo credit: Dr. I. Rojas.

Predisposing factors

• Factors that have the potential to stress or overstimulate the birds may contribute to cannibalism. Overcrowding, excessive heat, excessive light (length and intensity of the light exposure), sudden changes in management, shortage of feed and water, and introduction of new birds to the flock can predispose the birds to a cannibalistic behavior.
• Male to female ratio. Males can be very territorial. Having too many of them can lead to fighting, exposed wounds, and weakened/moribund birds that will be perfect targets for cannibalism.
• During oviposition the vent is clearly visible and its bright and shiny color invites pecking from flock mates. A bright nesting area may result in losses due to vent pecking and ensuing peritonitis.
• Some chicken breeds are more aggressive than others and will tend to peck weakened animals. In particular, lightweight breeds of egg-type chickens tend to be prone to cannibalistic behavior.
• Nutritional deficiencies. Nutrition also plays a role in cannibalism. Diets low in fiber, methionine, and salt have been particularly associated with cannibalistic behavior. 

Prevention

• Bird density.
  Make sure to provide enough space for the birds. For large breeds of chickens, 0.25 ft²/bird should be given for the first 2 weeks, 0.75 ft²/bird for 3-8 weeks of age, 1.5 ft²/bird from 8 to 16 weeks of age, and 2 ft²/bird from 16 weeks of age onwards. Please note that these are general guidelines and you should adjust based on the species and specific breed. The recommended density for a particular breed is normally listed in the management guide for the particular genetic line.
• Heat stress.
  Obviously, heat stress is more common during the summer months; however,  it can happen any time supplemental heat is used. Note that the recommended brooding temperature is initially high (92-93 °F). However, the temperature must gradually decrease on a weekly basis until it reaches 70-75°F when the birds are fully feathered (for details see the management guide for the particular genetic line you are using). Failure to reduce the brooding temperature is a common cause of cannibalism. Observe birds daily. If panting is identified, check the temperature with a thermometer. If the temperature is too hot for a particular age, adjust the heaters accordingly, and improve ventilation. Cold drinking water is a great way to dissipate heat during the hot summer months. To achieve this, provide adequate shade to the water tank, change water frequently from the drinkers, and/or flush the water lines during the hottest hours of the day.
• Nest comfort.
  Sufficient nest space, located in a quiet place that is protected from direct light, will keep the animals safe and comfortable while laying. The shaded area inside a nest helps to greatly reduce the event of vent pecking during oviposition. Another advantage of having a dedicated nest area is the production of much cleaner eggs since eggs that are laid on the floor tend to be heavily soiled.
• Light management.
  For meat birds, light should be bright enough for them to find their feed and to move within their environment. In general, they do not need much light. Light that is too bright will overexcite the animals and can lead to cannibalism. In general terms, layers will need light with greater intensity and for a longer duration compared to meat birds. Short days will make the birds stop ovulating, so light supplementation is a must in fall/winter. Even though light is important to keep the birds laying, they also need to rest. Make sure to provide a suitable "night time" when all lights are off. In general, a dark period of at least 4-6 hours is used in meat-type chickens and a period of at least 7-8 hours is used in egg-type chickens during full production.
• Give the birds something to do.
  Free-range birds will have plenty of distractions. If your birds are indoors, there are some alternatives to keep them distracted. If they are in cages, there are toys made of hard plastic and bright colors that can keep the animals busy for some minutes a day. If birds are raised on the floor, adding grass (e.g., clover, alfalfa) on the floor or on top of the feed will provide distraction for several hours. Birds love to peck and scratch over small patches of grass/hay. Be careful with providing too much grass to birds that are not used to it, especially if the individual fibers are long. This could lead to overconsumption and tangling of the fibers with other feed content in the crop originating a condition known as crop impaction.
• Beak trimming.
  If all strategies fail, consider gentle beak trimming especially in more nervous breeds.

Dealing with an ongoing case of cannibalism.

Cannibalism can lead to severe losses and animal suffering. In a short period of time, the cannibalistic behavior can become vicious. Such a learned behavior is very difficult to eradicate from a flock. Because of this, immediate action is required at the first sight of cannibalism. Remove injured birds as soon as possible, put them together in a separate pen, and cover their wounds with a dark ointment to disguise the blood and the brightness of the exposed flesh. Decrease the intensity of light and check the temperature. Place some alfalfa on the floor for distraction and fiber supplementation. In addition, review the prevention section and correct any management practices that may need adjustment.

Sources and recommended reading.

Poultry Cannibalism: Prevention and Treatment by Phillip Clauer. The Pennsylvania State University Extension Program.

Avian Diseases Manual. 7th ed. The American Association of Avian Pathologists.