Breast blisters in groups of slow-growing broilers in relation to strain and the availability and use of perches

1. The relationship between perching behaviour, availability of perches and the incidence and severity of breast blisters in broilers was investigated together with a comparison between two slow-growing broiler strains. 2. Sixteen single strain groups (n = 60) of Labresse and i657 broilers were subjected throughout the experiment to one of three perch availabilities: 15 cm per bird (Labresse and i657), 7.5 cm per bird (i657 only), and 0 cm per bird (i657 only) with 4 replicates per treatment. The birds were housed indoors from one day old, and at 43 d of age 52 birds from each group were moved to outdoor housing facilities with access to grass-covered outdoor areas until slaughter at 84 d of age. 3. The use of perches was monitored via video recordings throughout the experimental period. The severity of breast blisters was recorded on a scale from 0 to 2 at slaughter. 4. Groups of i657 with 15 cm perch per bird used these more than groups with 7.5 cm perch per bird (19% vs 8% of birds perching at midnight). A positive association between access to perches and severe breast blisters (score 2) was found in the groups of i657, with odds ratios of 3.1 and 3.4 for 7.5 and 15.0 cm per bird, respectively, relative to the no-perch treatment. 5. Labresse were more likely to develop breast blisters than i657 (odds ratio 3.5), but used the perches less (0.1 vs 9.5 birds perching at midnight) and weighed less (2011 g vs 2246 g) than i657. 6. Males had a higher incidence of breast blisters than females (odds ratio 12.2), and this was most prominent in the Labresse strain (odds ratio 40.0). 7. In some broiler strains access to perches may be associated with an increase in the occurrence of severe breast blisters, but strain and sex of broiler chickens appear to have a much larger influence than access to perches on the incidence of breast blisters.