Cannibalism in Free-Range Flocks Linked to Perches, Early Range Access

Vent pecking and cannibalism were observed in about one quarter of the UK free-range and organic laying flocks surveyed, and these behaviours were associated with early access to the range and the provision of perches and nipple drinkers, according to S.L. Lambton of the University of Bristol in a paper presented at the European Symposium on Poultry Welfare last year.
calendar icon 26 February 2010
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Vent pecking (VP) and cannibalism remain some of the biggest problems challenging free-range egg producers, with both economic implications for farmers and welfare implications for birds.

S.L. Lambton from the University of Bristol explained that this prospective epidemiological study investigated the development of vent pecking and cannibalism on 62 barn, free-range and organic UK farms (119 flocks).

Flocks were visited at 25 and 40 weeks, when rates of vent pecking, and incidence of cannibalism, were recorded. Environmental and management data were collected for each flock.

Factors affecting the development of these behaviours were modelled using the multilevel modelling program, MLwiN.

According to the Bristol researchers, VP was observed in 24.8 per cent of flocks, at a mean rate of 0.064 bouts per bird per hour. Cannibalism was recorded by farmers in 28.4 per cent of flocks. Farmers recorded the mean age of onset as 20.9 and 20.7 weeks for VP and cannibalism, respectively.

Risk of VP increased with rate of severe feather pecking (Z=5.43, p<0.001), at all ages, as did risk of cannibalism (Z=3.85, p<0.001).

Risk of VP decreased with a later age of light period increase (Z=3.29, p=0.001). This light increase is associated with the onset of lay, and often range access.

Interpretation of the correlation was complicated by an effect of range use: rate of VP at 40 weeks decreased with range use at 40 weeks (Z=11.58, p<0.001) but increased with range use at 25 weeks (z=3.99, p<0.001). Analyses suggested there was a detrimental effect of allowing range access before onset of lay.

A variety of other factors that could have been associated with range use were also significant, including:

  • an increase in risk of VP with pop hole size (Z=2.46, p=0.007)
  • use of perches more than 0.5 metres high increased the risk of vent pecking (Odds Ratio (OR)=6.94, Z=2.44, p=0.007)
  • use of perches increased the risk of cannibalism (OR=7.37, Z=3.02, p=0.003).
  • use of nipple drinkers increased the risk of VP (OR=6.26, Z=1.98, p=0.048), and it was hypothesised this was due to their use as perches.

Lambton and co-authors conclude that the risk of VP and cannibalism may be lowered by reducing the rate of severe feather pecking. Although the use of perches for birds during early rearing is thought to protect against vent pecking (Gunnarsson et al., 1999) allowing adult birds to perch presented a clear risk.

Risk of VP may also be reduced by delaying the onset of lay and subsequently encouraging range use, although more research is required to elucidate the interaction between the two factors.


Lambton S.L., T.G. Knowles, C. Yorke and C.J. Nicol. 2009. Risk factors affecting the development of vent pecking and cannibalism in loose housed laying hen flocks. Proceedings of 8th Poultry Welfare Symposium, Cervia, Italy, 18-22 May 2009, p13.

Further Reading

- You can see other papers presented at the 8th European Symposium on Poultry Welfare by clicking here.

March 2010
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