A Lower stocking density stimulates species-specific behavior and improves welfare of both fast- and slower-growing broilers

There is a trend towards broiler production systems with higher welfare
requirements, often including slower-growing broilers and a reduced stocking
density. Although we know that fast-growing broiler welfare improves when
stocking density reduces, it is unknown whether slower-growing broilers respond
in the same way to stocking density in terms of welfare. Thus, the aim of this study
was to compare the behavior and welfare of fast- (Ross 308) and slower-growing
broilers (Ranger Classic) housed at different stocking densities (24, 30, 36 and 42
kg/m2). Each experimental group was replicated 4 times, resulting in a total of 32
experimental pens. Behavior was observed at pen level using instantaneous scan
sampling at 4 target weights (0.4, 1.1, 1.7 and 2.1kg), where 2 locations of
approximately 3m2 were observed per pen. In addition, the novel object and
human approach test were performed once per pen at the same target weights to
assess fearfulness. Gait score, footpad dermatitis, hock burn, cleanliness and
injuries were assessed using the Welfare Quality® protocol at 2 target weights
(2.0 and 2.3kg), with 30 birds assessed per pen (15 male/15 female). No
interaction effects between breed and stocking density were found for any of the
variables, indicating that breeds responded in the same way to the different
stocking densities with regard to their behavior and welfare. Slower-growing
broilers showed less ingestion, but more active and foraging behavior, and further
had better scores for all welfare indicators compared to fast-growing broilers.
Broilers housed at lower stocking densities showed less ingestion, but more
foraging and comfort behavior, and further had better scores for all welfare
indicators compared to those housed at higher stocking densities. No clear
differences between breeds or stocking densities were found for behavioral
responses to the fear tests, except for a higher percentage of slower-growing
broilers approaching the human compared to fast-growing broilers. In conclusion,
regardless of breed, broilers housed at lower stocking densities showed more
species-specific behaviors and had improved welfare compared to those housed at
higher stocking densities. Further, slower-growing broilers showed more speciesspecific
behaviors and had improved welfare compared to fast-growing broilers.
These findings demonstrated that a lower stocking density is beneficial for behavior
and welfare of both fast- and slower-growing broilers.