Free range characteristics and use by chickens from two genetic lines

The free-range system improves chicken’s welfare and enriches their diet. There is little information about influence of chickens on the sward quality. The aim of the study was to identify differences in the chemical and botanical composition of the pasture sward used by chickens and to assess if frequency of chicken exits outdoors is associated with the botanical composition of the ranging areas. One hundred twenty non-beak trimmed mixed sex birds of Green-legged Partridge (GP) and Sasso line C44 (S) were used. Each pen had direct access to an individual outdoor range providing 10.5 m² per chicken, video-recorded continuously. Vegetation coverage regarding botanical composition was determined based on botanical-weight analysis from three control plots, while range use was calculated from the video material. The data were analysed by ANOVA model in SAS software (v 9.4). Regarding chemical composition, fiber content was higher in dry matter from the control pastures. Significantly more Dactylis glomerata (L.) and Alopecurus pratensis (L.) were observed on ranges used by Sasso. The higher share (%) of weeds and grasses was at the ranges used by chickens (weeds: S:8.66 (1.42) and GP:7.61 (0.59) and grasses: S:10.36 (0.96) and GP:12.10 (0.65)) as compared to control plots (1.45 (1.34)) and 3.86 (2.97), respectively) in contrast to legumes ((S:0.01 (0.01) and GP:0.32(0.26)) and sedges (S:0.64 (0.48) and GP: 0.09 (0.06)) most present in the control plots (10.88 (1.55)). Positive association between range use frequency and proportion of Heracleum sphondylium (L.), Rumex acetosa (L.), Festuca rubra (L.), and Lolium perenne (L.) was observed for Sasso, while foe Green-legged Partridges with proportion of Armoracia rusticana (L.), Stellaria media (L.), Ranunculus repens (L.), Cirsium arvense (L.) and Rumex crispus (L.). Concluding, the sward quality of the ranging areas was affected by the presence of the chickens and it differed between genotypes. Unknown remain if birds used the pasture more frequently depending on its botanical composition or if the pasture composition depended on the frequency of its uses by the birds.