Effects of dark brooders and overhangs on free-range use and behaviour of slow-growing broilers

Welfare of broilers on farm

This Scientific Opinion considers the welfare of domestic fowl (Gallus gallus) related to the production of meat (broilers) and includes the keeping of day-old chicks, broiler breeders, and broiler chickens. Currently used husbandry systems in the EU are described. Overall, 19 highly relevant welfare consequences (WCs) were identified based on severity, duration and frequency of occurrence: 'bone lesions', 'cold stress', 'gastro-enteric disorders', 'group stress', 'handling stress', 'heat stress', 'isolation stress', 'inability to perform comfort behaviour', 'inability to perform exploratory or foraging behaviour', 'inability to avoid unwanted sexual behaviour', 'locomotory disorders', 'prolonged hunger', 'prolonged thirst', 'predation stress', 'restriction of movement', 'resting problems', 'sensory under- and overstimulation', 'soft tissue and integument damage' and 'umbilical disorders'. These WCs and their animal-based measures (ABMs) that can identify them are described in detail. A variety of hazards related to the different husbandry systems were identified as well as ABMs for assessing the different WCs. Measures to prevent or correct the hazards and/or mitigate each of the WCs are listed. Recommendations are provided on quantitative or qualitative criteria to answer specific questions on the welfare of broilers and related to genetic selection, temperature, feed and water restriction, use of cages, light, air quality and mutilations in breeders such as beak trimming, de-toeing and comb dubbing. In addition, minimal requirements (e.g. stocking density, group size, nests, provision of litter, perches and platforms, drinkers and feeders, of covered veranda and outdoor range) for an enclosure for keeping broiler chickens (fast-growing, slower-growing and broiler breeders) are recommended. Finally, 'total mortality', 'wounds', 'carcass condemnation' and 'footpad dermatitis' are proposed as indicators for monitoring at slaughter the welfare of broilers on-farm.

Early life environment affects behavior, welfare, gut microbiome composition, and diversity in broiler chickens

This study aimed to identify whether early-life conditions in broiler chickens could affect their behavior and welfare, and whether or not this was associated with an altered gut microbiome composition or diversity. Broilers were tested in a 2 x 2 factorial design with hatching conditions [home pen (OH) or at the hatchery (HH)] and enrichment (dark brooder (EE) or no brooder (NE) until 14 days of age) as factors (N = 6 per treatment combination). Microbiota composition was measured in the jejunum on days (d) 7, 14, and 35 and in pooled fecal samples on day 14. A novel environment test (NET) was performed on days 1 and 11, and the behavior was observed on days 6, 13, and 33. On day 35, composite asymmetry was determined and footpad dermatitis and hock burn were scored. In their home pen, HH showed more locomotion than OH (P = 0.05), and NE were sitting more and showed more comfort behavior than EE at all ages (P <0.001 and P = 0.001, respectively). On days 6 and 13 NE showed more eating and litter pecking while sitting, but on day 33 the opposite was found (age^*enrichment: P = 0.05 and P <0.01, respectively). On days 1 and 11, HH showed more social reinstatement in the NET than OH, and EE showed more social reinstatement than NE (P <0.05). Composite asymmetry scores were lower for EE than NE (P <0.05). EE also had less footpad dermatitis and hock burn than NE (P <0.001). Within OH, NE had a more diverse fecal and jejunal microbiome compared to EE on day 14 (feces: observed richness: P = 0.052; jejunum: observed richness and Shannon: P <0.05); the principal component analysis (PCA) showed differences between NE and EE within both HH and OH in fecal samples on day 14, as well as significant differences in bacterial genera such as Lactobacillus and Lachnospiraceae (P <0.05). On day 35, PCA in jejunal samples only showed a trend (P = 0.068) for differences between NE vs. EE within the OH. In conclusion, these results suggest that especially the dark brooder affected the behavior and had a positive effect on welfare as well as affected the composition and diversity of the microbiome. Whether or not the behavior was modulated by the microbiome or vice versa remains to be investigated.

Why-Oh-Why? Dark Brooders Reduce Injurious Pecking, Though Are Still Not Widely Used in Commercial Rearing of Layer Pullets

Dark brooders, i.e., horizontal heating elements for chicks equipped with curtains, mimic some aspects of maternal care, such as the provision of heat and a dark area for chicks to rest. Thus, they can be considered as artificial passive replacements of a mother hen. Despite their advantages in animal welfare and the likely positive outcomes in production and economy, dark brooders are rarely used in commercial layer pullet facilities. The main positive effect on welfare is a reduction of injurious pecking during the rearing and laying periods, which results in improved feather cover and reduced skin injuries and mortality due to cannibalism. Other welfare benefits include improved rest in dark-brooded chicks and reduced fearfulness at all ages tested (i.e., from 4 to 26 weeks). The impact on production and economy is seen in a reduction of the energy costs in the first weeks of life due to radiant heating, as well as improved total egg production and reduced floor egg laying. The aim of this paper is to review the existing literature on the effects of dark brooders on injurious pecking and other welfare issues in layers, including speculations on the possible explanations for improved welfare. We also discuss the possible reasons for why dark brooders are not applied more commonly in commercial practice, including insufficient information on the economic aspects of using brooders and the lack of commercially available brooder options.