The use of partially slatted floor designs as an alternative to littered systems in broiler chickens. II. The effects on welfare and behavioral traits.

This study investigated the effects of different flooring designs on the welfare and behavioral traits in fast-growing broilers. A total of 600 day-old Ross-308 chickens were randomly allocated to five treatment groups: fully littered (FL), fully slatted (FS), and combined systems with varying slatted floor ratios (1/3SF, 1/2SF, and 2/3SF). Welfare parameters, including body defects, gait score, and tonic immobility (TI), along with behavioral activities, were assessed. Results indicated that hock burn and breast skin burn scores were significantly higher in male birds and increased with the proportion of slatted flooring (p < 0.001). Conversely, the FS and high-ratio slatted groups exhibited significantly better body cleanliness and breast feathering scores compared to the FL group. While gait scores were generally poorer in males, the floor design significantly influenced walking ability (p = 0.05), with higher impairment observed in FS males. TI duration did not differ significantly among treatments. Behavioral observations revealed that the FL system promoted active behaviors, particularly foraging and locomotion (p < 0.001). In contrast, the FS system inhibited natural behaviors such as dust bathing and foraging, leading to increased preening and passive behaviors. In conclusion, while slatted floor systems offers advantages in hygiene and cleanliness, it negatively impacts leg health and restricts the expression of natural behaviors. Partially slatted floor systems presented intermediate results but did not fully mitigate the welfare trade-offs associated with slatted systems.