Active walking in broiler chickens: a flagship for good welfare, a goal for smart farming and a practical starting point for automated welfare recognition

Equivalence Between Optical Flow, the Unrest Index, and Walking Distance to Estimate the Welfare of Broiler Chickens

Modern poultry production demands scalable and non-invasive methods to monitor animal welfare, particularly as broiler strains are increasingly bred for rapid growth, often at the expense of mobility and health. This study evaluates two advanced computer vision techniques-Optical Flow and the Unrest Index-to assess movement patterns in broiler chickens. Three commercial broiler strains (Hybro®, Cobb®, and Ross®) were housed in controlled environments and continuously monitored using ceiling-mounted video systems. Chicken movements were detected and tracked using a YOLO model, with centroid data informing both the Unrest Index and distance walked metrics. Optical Flow velocity metrics (mean, variance, skewness, and kurtosis) were extracted using the Farnebäck algorithm. Pearson correlation analyses revealed strong associations between Optical Flow variables and traditional movement indicators, with average velocity showing the strongest correlation to walked distance and the Unrest Index. Among the evaluated strains, Cobb® demonstrated the strongest correlation between Optical Flow variance and the Unrest Index, indicating a distinct movement profile. The equipment's movement and the camera's slight instability had a minimal effect on the Optical Flow measurement. Still, its strong correlation with the Unrest Index and walking distance accredits it as an effective method for high-resolution behavioral monitoring. This study supports the integration of Optical Flow and Unrest Index technologies into precision livestock systems, offering a foundation for predictive welfare management at scale.

Genetics of gait score in broilers: Genetic parameters of gait score in purebred broiler lines

Leg health assessment is a vital component of poultry breeding goals; it includes a range of skeletal disorders and contact dermatitis traits as well as a general assessment of a bird's walking ability in the form of gait score (GS). If trained scorers are used, GS correlates well with more objective walking assessment methods and allows for high throughput data collection from large numbers of individuals. The paper describes for the first time GS heritabilities for broilers. The Aviagen GS system (AGS) consists of an 8-class scale of 10-45 in increments of 5, whereby 10 is the best score and 45 the worst. It has sufficient variation between categories to enable a clear distinction of GS classes for selection purposes. The results of GS at 4-5 weeks of age show GS heritabilities between 0.14 and 0.24 which is higher than turkey (0.08-0.13) or duck (0.06-0.12) heritabilities. Genetic correlations with body weight and breast percentage were unfavorable but moderate. Correlations among leg health traits (AGS, long bone deformities, crooked toes, hockburn and footpad dermatitis) were generally low (-0.16-0.10) for most traits and lines. While genetic correlations between AGS and production traits were unfavorable, both AGS and other leg health and production traits can be improved simultaneously in a multi-trait selection strategy combining production and welfare characteristics. AGS has been included in the Aviagen breeding goal since 2011.

Partial replacement of soybean with local alternative sources: effects on behavior, cecal microbiota, and intestinal histomorphometry of local chickens

Interest in partially replacing soybean meal in poultry diets with alternative protein sources such as agri-industrial by-products and black soldier fly (BSF, Hermetia illucens) has gained significant attention due to sustainability concerns. This study aimed to evaluate the effects of broiler diets in which soybean meal was partially substituted with agri-industrial by-products with or without BSF larvae meal, on the behavior, intestinal histomorphometry, and microbiome profile of a local broiler chicken strain. There were three dietary treatments. (1) A corn-soybean-based diet (Control), (2) a diet in which soybean was partly replaced (SPR) with local agri-industrial by-products, namely sunflower meal, brewers' dried grain, and wheat middlings, and (3) a diet in which BSF (5%) meal was added to SPR (SPR+BSF). Behavior was recorded on days 14, 35, and 49 at the pen level. On day 55, intestinal segments and cecal contents were collected from eight chickens per pen for histomorphometry and microbiome analysis. Dietary manipulations did not affect the behavior of broiler chickens (P > 0.05) suggesting that the experimental diets had no influence on behavior. A significant interaction between the intestinal segment and diets revealed that the SPR and SPR+BSF diets decreased duodenal villus height (VH) compared to the control diet (P < 0.05). However, this effect was not consistent across all of intestinal segments. Diet did not affect villus height to crypt depth ratio (VH/CD; P > 0.05), indicating no significant impact on the absorptive capacity of the digestive system. Firmicutes and Bacteroidetes were the dominant phyla in the cecal samples. Colidextribacter and Oscillibacter spp. were more abundant in chickens fed the SPR diet compared to those fed the control diet. The SPR+BSF diet resulted in higher abundance of Rikenella and Colidextribacter spp. compared to the control diet, while Desulfovibrio, Ruminococcus torques group, and Lachnoclostridium were more abundant in the ceca of birds fed the SPR diet than those fed SPR+BSF. In conclusion, replacement of soybean with agri-industrial by-products and BSF larvae meal could regulate the cecal microbiota composition without negatively affecting the behavior and intestinal histomorphometry of the local chickens.

The potential of pumice as a litter material and its influence on growth performance, carcass parameters, litter quality traits, behavior, and welfare in broiler chickens

This study evaluated the possibilities of pumice (light stones) as litter material in broiler production. Experimental treatments included wood shavings (WS), acidic pumice (AP), and basic pumice (BP) alone, and in combination; wood shaving + acidic pumice (WSAP) and wood shaving + basic pumice (WSBP) in a ratio of 1:1. Two trials were performed, one in summer, and the other in winter. Each trial involved 750 mixed-sex Ross (308) broilers. Also, there were 15 replicate pens with 50 broilers and a stocking density of 12.5 birds/m2 for each pen at the beginning of each trial. Performance, litter quality, carcass parameters, body and leg abnormalities, body temperature, fear and stress responses, proportional asymmetry, and some behavior expressions were investigated. The litter treatment influenced the final live body weight, litter moisture, ammonia concentration, footpad dermatitis, hock burn, breast blister, hot carcass yield, heart, liver, spleen, abdominal fat, wing and neck ratio, breast and back cleanliness, and the expression of dust bathing and foraging behaviors (P < 0.01; P < 0.05). Furthermore, there was a seasonal effect on live body weight, feed conversion ratio, livability, litter pH, 42-day litter moisture, hot carcass yield, back cleanliness, footpad dermatitis, hock burn, footpad temperature, heterophil-to-lymphocyte ratio, and expression of pecking behavior (P < 0.01; P < 0.05). It is suggested that acidic pumice stone alone or in a mixture with wood shavings could be used as a reliable litter material, alternative to wood shavings.