Cannibalism in laying hens : characteristics of individual hens and effects of perches during rearingYngvesson, Jenny
Cannibalism causes severe welfare and economical problems in modem egg production. This thesis aimed to identify differences between cannibalistic, pecked and neutral individuals and to investigate possible mechanisms for why perches reduce cannibalism. It combines theories and hypotheses from behavioural ecology and practical poultry production.
Individual characteristics were investigated in birds collected from commercial farms experiencing outbreaks of cannibalism. Birds were either classified as cannibals, victims or controls. The theory ofdevelopmental stability predicts that individuals with low stress tolerance show more fluctuating asymmetry. Cannibals were found to be larger than victims and both cannibals and victims were found to be more asymmetric than control birds, which may indicate that they are less stress tolerant.
Cannibalistic behaviour can be triggered by food shortage or nutritional deficiencies. Cannibals were therefore predicted to show signs of nutritional deficiency. However, no differences were found in body weight, production efficiency or resource allocation. Oviposition duration and egg weight was investigated as possible causes for why certain individuals become victims of cloacal cannibalism, but no differences were found between these individuals and control birds.
Earlier research has found that perches reduce mortality caused by cannibalism. In this thesis, rearing without perches was found to reduce spatial skill in layers and this effect was long lasting, even though birds were trained to use perches. Rearing with perches was also found to reduce latency and increase number of birds jumping up onto perches in a simulated cannibalistic attack. Merely providing perches, however, did not guarantee that birds would learn to use them and there was a large individual variation in whether or not birds learnt to perch.
In summary, cannibalism in laying hens has some similarities to cannibalism under natural conditions. It is also suggested that in commercial poultry rearing, a practical way to reduce cannibalism in loose housing systems is to ensure that birds learn to perch within the first few weeks ofthe rearing period.
KeywordsLaying hens; cannibalism; body size; fluctuating asymmetry; production; egg laying; perches; rearing; escape behaviour; welfare
Published inActa Universitatis Agriculturae Sueciae. Veterinaria
2002, number: 120
Publisher: Swedish University of Agricultural Sciences