In recent decades, the walking abilities of broilers have changed due to intensive selection for rapid growth, high feed efficiency and increased final weight. The study by the Department of Animal Sciences at Aarhus University shows that broilers with relatively minor gait changes (not limping as such), showed an increased level of inactivity and were less mobile and exhibited a greater number of abnormal behaviors compared to normal gait birds.
Assessment of gait in broilers
When the walking skills of broilers are assessed, the Bristol scale with scores of 0 to 5 is generally used. A gait score of 0 (GS0) is equivalent to normal gait birds while GS5 birds are unable to walk. In the broiler industry and scientific literature, GS3-5 birds are classified as lame while GS1-2 scores describe reduced walking abilities without actual lameness. Although GS1-2 is among the most frequent scores in conventional broiler flocks, only a few studies have focused on this group.
Study of GS2 chickens at Aarhus University
Under the direction of lead researcher Anja Brinch Riber, a study was conducted at the Department of Animal Sciences at Aarhus University, to better understand how reduced walking skills affect birds – in this case by comparing the behavior of birds. GS2 chickens (all Ross 308) with comparable behavior of normal gait birds. The project included observation of undisturbed behavior in the domestic environment, mobility tests and included health data collected during slaughter.
“We don’t often have the opportunity to study broiler welfare by following the same individual over time. We were able to do this in this project, which is why it is an atypical project, bringing new knowledge on, for example, the evolution of walking abilities over time and the consistency between different performance indicators. well-being in the same individuals. Our experimental birds were housed in conditions similar to those of practice during the first three weeks of their life in order to best model reality ”, explains Anja B. Riber.
Less mobility and increased abnormal behavior in GS2 chickens
The results of the study show clear differences between GS0 and GS2 birds with regard to mobility and undisturbed behavior. GS2 birds were less mobile, more inactive, and exhibited more abnormal behaviors such as feeding while sitting. Additionally, GS2 birds exhibited less natural behavior such as using perches and comfort behavior. These results show that GS2 may be important for the welfare of birds.
In addition to studying behavioral differences in birds rated GS0 and GS2, the effects of gender and the effects of treatment with the analgesic drug carprofen were included in the study. Carprofen is a nonsteroidal anti-inflammatory drug, previously used in mobility and pain studies in broilers.
“It may seem odd to give animals analgesic medication if you don’t know if they are in pain, but comparing the responses of animals treated with analgesic drugs versus control animals is a classic method of documenting whether pain is involved.” says senior researcher Mette S. Herskin, who participated in the study. “If the animals change their behavior after administration of an analgesic drug, it suggests that pain may be involved. A similar method was used to study pain, for example in relation to castration of piglets and dehorning of calves, ”she explains.
Comparison of broilers with and without administration of analgesic drugs showed that carprofen affected undisturbed behavior, resulting in increased physical activity. It is important to note, however, that the effects of carprofen did not depend on the birds’ walking score. Therefore, these results may indicate that broilers in general may be behaviorally limited due to pain, but it should be borne in mind that carprofen may have effects other than pain relief. pain and therefore further studies are needed for further clarification.