Lead

Motivational Basis

Development

Prevalence

Causes

• light, crowd size, over heating, nutrition, farm styles, other injured birds present, genetics, nurture

Nature vs Nurture

Methods of control

Cannibalism in poultry is the act of one individual of a poultry species consuming all or part of another individual of the same species as food. It commonly occurs in flocks of domestic hens reared for egg production, although it can also occur in domestic turkeys, pheasants and other poultry species of any age or breed.^[1] Poultry create a social order of dominance known as pecking order. When pressure occur within the flock, pecking can increase in agression and escalade to cannibalism.^[1] As well, cannibalism can occur as a consequence of feather pecking which has caused denuded areas and bleeding on a bird's skin. Cannibalism can cause large mortality rates within the flock and large decreases in production due to the stress it causes. Vent pecking, sometimes called 'cloacal cannibalism', is considered to be a separate form of cannibalistic pecking as this occurs in well-feathered birds and only the cloaca is targeted. There are several causes that can lead to cannibalism such as: light and overheating, crowd size, nutrition, injury/death, genetics and learned behaviour.^[1][2][3] There is research that is conducted to attempt to understand why poultry engage in this behaviour as it is not totally understood. But there are known methods of control to reduce cannibalism such as crowd size control, beak trimming, light manipulation, perches, selective genetics and eyewear.

Poultry in captivity is where most cannibalistic behaviours are observed. Due to this, there are many factors that can cause cannibalism. Some of these factors are outline below:

High intensity light with prolonged exposure can lead to cannibalism of poultry in captivity due to the increase of stress and overheating that causes discomfort.^[1]

Poultry have a social hierarchy and when crowds are too close together dominant birds will fight more often to obtain or sustain dominance which can increase risk of cannibalism. ^[1] The increase crowd size also plays into a few more factors. With larger crowd there is less space in the pen. This allows for less feeding space and decreased feeding spaces means that dominant birds will take majority of the food supply leaving less dominant birds susceptible to becoming underweight and therefore easier targets to the dominant birds for cannibalism.^[1] An optimal flock size are either large flock of greater then 30 where the group is too large to recognize an established dominant bird and the social hierarchy breaks down, Or a small group size where a social order can easily organize itself .^[1] Intermediate group sizes cause confusion among the flock and leads to higher agression of different birds attempting to become the dominant one and therefore leading to increased risk of cannibalism. ^[1]

A particular diet of low protein but high energy is shown to lead to less agressive behaviours, but in saying that, a diet lacking the protein methionine is shown to cause agressive behaviours. ^[1]Methionine is an essential amino acid. ^[4]This means the body cannot produce the amino acid and needs an external source to obtain its required amount. Often times in flocks it is the first limiting amino acids^[4]. One reason as to why methionine could lead to agressive behaviour is because it Methionine contains sulfur.^[4] This sulfur is often times used by the bird to make feathers.^[4] When this amino acid is deficient poultry will pecking and feather eat other birds to receive their required amounts.^[4] This behaviour could then escalate to turning into cannibalism.

Poultry have a glad called the preen gland that secrets and oily salty tasting substances. When their diets lack salt, the gland produces the oily substances but without the salty taste. The bird then believes it is not getting its requirement from the gland and will peck at other birds preen gland to meet their requirements. When the behaviour of pecking other birds is introduced, it can lead to increased risk of cannibalism.^[1]

When feeding, it is important to give enough space and to lay the feed to mimic the environmental conditions and spread the feed so poultry spend time pecking at the food and not each other. ^[1]

Feather eating is another potential cause to cannibalism. Feather eating a behaviour similar to feather pecking where poultry will peck at other members of the flock to eat their feathers.^[2]In a study of F2 cross of hens for aggressive pecking behaviour it was seen that feather eating during a chicks rearing stage of life meant it had a higher likelihood of feather pecking in the laying stage of its life.^[2] One reason they believed why feather eating was prevalent is that keratin from feathers was not uses a nutritional source per say, but could enhance the gut microbiome. ^[2]

Within a pen, if another bird is injured or dead, the sight of this can insinuate other pen members to engage in cannibalistic behaviours.^[1] This is due to the social order created by poultry, as well as their attraction to blood .^[1]Poultry are attracted to the colour red and the sight of blood can cause them to be attracted to the injured bird and peck at it more to increase their rank in the pecking order.^[5] Sometimes this even leads to their death.^[5]

While cannibalism of poultry is a learned behaviour, there is a genetic component that can make the bird be more susceptible to engaging or initiating cannibalism.

Pecking and other forms of pecking (feather pecking, vent packing, agressive pecking) are normal behaviours that have genetic influences ^{[1][2] [3]} One study that performed in the Netherlands was testing if a specific farming style had an effect on cannibalism. During the study they estimated the heredity of feather pecking to be as high as 0.56^[3] Another study found that brown-egg laying hens are more likely to engage in feather pecking then white-egg laying hens. ^[1]The genetics of poultry will not guarantee a bird will engage in cannibalism, but the genes a bird possesses play a part in the degree of aggressiveness a bird could engage in feather pecking and increases their risk engaging in cannibalism.

Certain genetic technologies such as linkage analysis could identify genes related to feather pecking and could be screen against to select birds that are less likely to engage in pecking.^[3] Unfortunately one study found a correlation between feather pecking and egg production and found that birds that engage in high feather pecking behaviour, had on average had a higher egg production.^[2] Therefore selecting against feather pecking could reduce egg production. Farmers would have to chose between a trade off of either possibly having higher egg production with a high potential of flock death due to cannibalism, versus lower egg production with a lower risk of death due to cannibalism.

As mentioned before, pecking and feather pecking are normal behaviours, but cannibalism can be learned. Feather eating is also a normal behaviour that can lead the bird into engaging in feather pecking. As a chick during rearing, if a chick engages in feather eating, there are more likely to engage in feather pecking during the "laying' stage of their lives.^[2] Furthermore, if a member of the flock has been feather pecked on, they will stay in this category as the damage to the feathers are a physical indicator to others that that bird is being targeted.^[2]One study found that fear could increase feather pecking and primary cannibals can influence secondary cannibals by initiating cannibalism by becoming more agressive in pecking. ^[2] Cannibalism within a flock is seen as a chain reaction where if one member of the flock begins, if left unattended, will cause others around it to learn the behaviour and engage in cannibalism. ^[3]The social order of a flock will also play into the risk of cannibalism. This can be seen if a primary cannibal is a higher ranked bird in the flock, it could influence more secondary cannibals and spread this behaviour more rapidly.

While genetics and learned experience can influence behaviour, ultimately it is an interaction of the two that gives the expressed behaviour. The Netherland study found the flocks of the same breed had different outcomes of whether cannibalism developed or not depending of the management control of the different farms the flocks grew up in.^[3] While the genetics of these flocks were similar, the environmental factors ultimately influences the introduction of cannibalism in the flocks. In some flocks 36.4% of the deaths due to cannibalism was observed.^[3] To minimize cannibalism in domesticated poultry different approaches such as ecology, environmental physiology, epidemiology, molecular genetics and ethology, but the approach with the most success was the molecular genetic with behavioural research and could lead to the decline of server practices to reduce cannibalism such as beak trimming.^[3]

Beak-trimming is the most common method of preventing or reducing injuries by cannibalism. In a three-year study of floor-housed laying hens, death by cannibalism was reported as 7% in beak-trimmed birds but was increased to 18% in non-trimmed birds. This method can be consider cruel as it can cause acute and chronic pain to the bird.^[6] The beaks of poultry are highly sensitive to touch, heat and pressure. Trimming their beaks loses their ability to sense the external world and could causes neuromas which are bundles of severe nerve endings that became exposed due to beak trimming. ^[6]

^{[1][2][3][4][5]}

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Source "feather pecking and cannibalism in small backyard poultry flocks

• evidence to suggest hens that lay brown eggs engage in feather pecking more often then white egg laying hens ******
• hierarchy of pecking order to establish dominance
• mild pecking is normal within pecking order but can escalate into cannibalism
• caged and small group sizes allow for pecking order to be established easier and therefore there are less problem within the social group
• seen throughout the poultry group such as chickens, ducks, turkeys, quail, and pheasants at any age of any breed
• cannibalism is a learned behaviour *****, poultry only begin this behaviour by observing another member exhibit the agressive behaviour
• the cause has a genetic component *****
• Causes of cannibalism/feather pecking
  • over crowding- poultry to close together will fight more often for dominance and to protect their food/resources, which ultimately can lead to cannibalism. As well enough space for simultaneous feeding, will discourage less dominant birds to become underweight fall victim to cannibalism
  • overheating- cause them to be uncomfortable and prone to pecking
  • lighting- high intensity and long duration of light can insinuate cannibalistic behaviour
  • Nutrition- high energy and low protein diets shown to lead to agressive behaviour. Particularly protein deficiency methionine**. when raising poultry, mick the foraging behaviours so they spend more time pecking at their food and not their pen mates. Diets lacking salt cause the preen gland to release oil without the salt taste it usually gives and therefore they will peck at other birds preen glands to satisfy their requirements.
  • injury/death- chickens are attracted to blood ** and an injured bird can cause an initiation of cannibalism within the flock due to their social order
  • intermediate size flocks- with large groups members of the flocks cannot individually recognize everyone and the social order breaks down into a tolerable group. In small groups that social order is established easily. therefore intermediate groups of about 30 cause a weird middle ground
  • feather pecking is a genetic trait

source Cannibalism by poultry

• The practice of beak trimming is associated with both acute and chronic pain and should not be practiced indiscriminately. Neuromas, tangles of severed nerve endings in the amputated beak stump, sometimes result from beak trimming.
• The avian beak is highly innervated and, like the human hand, is very sensitive to touch, temperature and pressure. Chickens use their beaks not only for gathering food but also for exploring and manipulating objects in the environment, preening, dustbathing, nesting and social interactions. Beak trimming is not only painful, it deprives the bird of important sensory information. However, if alternatives have been exhausted, a careful beak trimming program will prevent most cannibalism outbreaks.

source CANNIBALISM IN EXTENSIVE POULTRY KEEPING: INTERFACING GENETICS AND WELFARE

• cannibalism was seen in extensive farming environments
• 1994 on two extensive farming conditions farms, poultry were raised in the Netherlands and it lead to cannibalism:
  • On the question how the pecking started one farmer responded ‘by extreme feather pecking’, one ‘by extreme pecking between cloaca and legs’, and nine ‘by cloaca pecking’. The inventory showed that mortality due to cannibalism is sometimes very high (range 0-30%). The problems for the ‘animal friendly’ egg market are thus very serious

• Cannibalism can take several forms, i.e. toe picking in chicks, feather pulling, head, tail or body pecking, and vent pecking in older birds
• Vent pecking often starts after the start of laying and is an indication that cannibalism is influenced by the hormonal system
• showed that fear is related to feather pecking, found that fearful hens - shown in the tonic immobility-test (TI) - showed more feather pecking.
• Primary cannibals cause other hens to practice cannibalistic behaviour
• found a significant trend of finding a second cannibalised hen after finding the first one in a cage
• found in one of the six groups extreme cannibalism in which group 9% of the animals was doing 50% of the vent pecking
• After 36 weeks significant differences between the pecking behaviour and between the mortality due to cannibalism (up to 34.6%) of the lines was found. There was surprisingly no relation between the pecking and the cannibalism. In floor housing no differences were found. In cages breed differences in pecking behaviour appeared to be related to differences in light intensity, stocking density, diet and group size. found comparable interactions between breeds and housing conditions in the same leghorn lines concerning pecking and cannibalism.
• Estimates of the heritability of feather pecking range from .04 to 0.10, Omission of families, that show no feather pecking, increased the heritability to 0.56, suggesting a strong genetic component
• Genetic correlation between feather pecking and plumage cover and body weight have been found. found severe feather pecks to be heritable and associated with behavioural activity, but not related to gentle feather pecking and aggressive pecking
• genotype-environment interaction concerning feather pecking dependent on experience with feathers as a substrate during rearing. Often large differences in feather pecking and cannibalism are found between breeds, and even flocks of the same breeds, may show large differences under different management conditions.
• With a set of high polymorphic microsatellite markers a ‘total genome scan’ procedure can be done. Segregation for behavioural parameters may reveal chromosomal regions that are basic to cannibalism or related traits by identification through ‘linkage analysis’
• Molecular genetic techniques can probably identify gene-complexes responsible for feather pecking and cannibalism.
• Such first reactions can be described as acute stress reactions or emotional expressions (Wiepkema et al. 1992). Vocalisations are often such emotional expressions (Koene 1991). For instance, birds receiving severe aggressive pecks often vocalise. Thus sound could be a welfare parameter related to the occurrence of a welfare problem (e.g. unstable rank-order)
• Heritabilities indicate that selection against feather pecking and/or cannibalism in laying hens may be successful
• A multi-disciplinary approach and effort - ecology, environmental physiology, epidemiology, molecular genetics and ethology - may solve the problem of cannibalism in free-range chicken. The molecular genetic approach in combination with behaviour research seems to be the most promising. If successful, and beak trimming is no longer necessary, also billions of intensively kept chicken may benefit from such an effort.

Source Genetic parameter for feather pecking and agressive behaviour in a large f2 cross

• Aggressive pecks are delivered in an upright body posture and are mainly directed toward the head of the recipient birds
• Recent investigations have shown that one motivation for feather pecking is the consumption of feathers
• It has been speculated that feathers may have a specific dietary effect. Feather keratin might not contribute much to the protein supply of the birds due to its low digestibility, but it might influence the function of the gastrointestinal tract via its structural components and the microbial activity following degradation
• If selection against feather pecking or aggression is to be performed, this might result in a reduced egg production because of the positive genetic correlations, especially for FPD and LE, but also for APD and LE
• In the 5th generation, egg number and egg mass in the low feather pecking line were higher than those in the high feather pecking line during a 4-wk trial
• The positive correlation between FPD and FE (Table 4) supports the hypothesis that FE and FPD have a common genetic basis. several explanations:
  • if you eat feathers during your rearing period it was shown that you would engage in feather pecking during your laying period
  • eating feathers changes the gut microbiome and enhance why it is still prevalent

• this study showed that if you were poultry that received feather pecking, that you would stay in this category permanently. one explanation is the feather damage becomes a marker for other hens to engage in feather pecking on you.
• In conclusion, the behavior traits feather pecking and aggressive pecking delivered and aggressive pecking received (FPD, APD, and APR) are heritable, and selection might help to reduce feather pecking and aggressive pecking. Selection against these traits might result in an unfavorable correlated selection response reducing egg production