An automated positioning system for monitoring chickens' location: Effects of wearing a backpack on behaviour, leg health and production

Automated tracking of the location of individual chickens is becoming more common in behavioural research. This technology has several advantages including gathering large amounts of data and monitoring of individual animals as opposed to flocks. To ensure the quality of the research the transmitters or tags attached to the bird as part of the automated positioning system should not have any effect on bird behaviour, welfare and production. Tag-related effects may lead to unreliable results which cannot be extrapolated to untagged birds. Therefore, we tested the effects of wearing a backpack containing a tag as part of an ultra-wideband system for automated position monitoring. The chickens' behaviour, leg health, cleanliness and body weight gain were studied. Sixty slow-growing broiler chickens (Sasso XL451) were housed in groups of 10 birds. Per pen, five birds were fitted with a 36-g tag (TAG) in a backpack from day 35-70 and the other five were identified using colour markings (CON). Behavioural observations from video recordings of TAG and CON chickens were performed twice daily (15-min periods) every other day. Birds were weighed on day 35 and 70, and on day 70 foot pad and hock dermatitis, gait, and cleanliness were scored. TAG birds walked less than CON birds in week 6, but this difference was absent from week 7 onwards. CON birds pecked more at TAG birds than other TAG birds did in week 6, probably due to the novelty of the tags, whereas the TAG birds could investigate their own tag instead of pecking at other birds' tags. No significant differences were observed for scores for foot pad and hock dermatitis, gait and cleanliness scores or weight gain between TAG and CON birds. These results indicate that the backpacks with tags had only minor, non-persistent effects on slow-growing broiler chickens' behaviour. The effects of colour-marking on behaviours observed in this study are likely to be small. The results indicate that the tags can be used for further studies in which these behaviours, welfare measures and production parameters play an important role.