The Impact of Perch Space on the Activity, Behaviour and Leg Health of Meat Chickens

Compromised leg health is a welfare and economic concern for meat chickens. Enrichment of the production environment via the provision of perches has been a focal point of research into reducing the prevalence of leg disorders in recent years. Despite inconsistent evidence of the effect of perches (Groves and Muir 2013; Phibbs et al. 2019), they are provided in almost two thirds of the Australian meat chicken industry, with 2.7 m perch/1000 birds required under the RSPCA Approved Farming Scheme (RSPCA Australia, 2019). This study aimed to evaluate whether the quantity of perch space provided impacts bird activity, behaviour and leg strength.

Day-old mixed-sex Cobb 500 chicks were randomly allocated across four perch space/1000 bird treatments viz: 2.7 m (A); 5.4 m (B); 47.6 m (C) and 0 m (D – control). Perches were an A-frame wooden design, with treatments A and B having one perch, 15 cm off the ground and treatment C having two perches, 15 cm and 30 cm off the ground. All perches were squared and 42 mm wide. The study took place in deep litter pens each housing 84 birds, stocking density 28kg/m² at 42 days of age (d), in a controlled environment shed, with six replicates/treatment. Overall feed consumption and bird weight from 0 d to 42 d were measured. Litter pH and moisture were measured biweekly throughout study. Bird activity was observed at five consistent time points every second day, starting at 1 d. At each time point birds using the perches were counted. Separately, all birds were classified into a behavioural category: eating, active, drinking or resting, the latter of which included perching birds. At 35 d, nine visually male birds were selected/pen for latency to lie (LTL) testing, after which they were scored for hock burn (HB), footpad dermatitis (FPD) and leg symmetry (LS). At 42 d, nine different visually male birds were selected/pen for the same scoring before being euthanased, scored for tibial dyschondroplasia (TD), detached femoral caps (DFC) and had one toe collected for bone ash (BA). Analysis was performed using IBM SPSS Statistics version 24.

For all perch treatments, perching peaked in week 3 and declined thereafter. Perching rate (average % of population perching at any given time point) was influenced by availability of perch space, with treatment C inducing the highest rate (P = 0.005). Perches had no effect on other activity categories. There was no effect of treatment on weight gain, FCR or litter moisture, but notably litter pH was lowest in treatment C (P = 0.002). There was no effect of treatment on physiological observations (HB, LS, TD, DFC, BA) except for FPD, where prevalence was lowest in treatment C at both 35 d (P = 0.011) and 42 d (P=0.037). No significant differences were observed in LTL at 35 d, but at 42 d control birds (treatment D) had the longest LTL (P = 0.059), followed by treatments A, B and C respectively.

Despite more perch space reducing FPD, no benefit of perches was seen in bird LTL, suggesting that perches may not enhance bird mobility, as reported by Phibbs et al. (2019) but contrary to Groves and Muir (2013). Further research into perch space and the impact of perches on leg strength in current day meat chickens is required to clarify these results.

ACKNOWLEDGEMENT: D.V. Phibbs is the recipient of the 2017 RSPCA Australia Scholarship for Humane Animal Production Research.