Effects of ground robots on hen floor egg reduction, production performance, stress response, bone quality, and behavior

Authors: LI, GUOMING - Mississippi State University; HUI, XUE - Henan Agricultural University; ZHAO, YANG - University Of Tennessee; ZHAI, WEI - Mississippi State University; Purswell, Joseph - Jody; PORTER, ZACH - Mississippi State University; POUDEL, SABIN - Mississippi State University; JIA, LINAN - Mississippi State University; ZHANG, BO - Mississippi State University; CHESSER, JR, GARY - Mississippi State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2022
Publication Date: 4/22/2022
Citation: Li, G., Hui, X., Zhao, Y., Zhai, W., Purswell, J.L., Porter, Z., Poudel, S., Jia, L., Zhang, B., Chesser, Jr, G.D. 2022. Effects of ground robots on hen floor egg reduction, production performance, stress response, bone quality, and behavior. PLOS ONE. 17(4). https://doi.org/10.1371/journal.pone.0267568.
DOI: https://doi.org/10.1371/journal.pone.0267568

Interpretive Summary: Reducing floor eggs in cage-free hen housing systems is a primary concern due to concerns over flock productivity and food safety. Current methods to limit floor eggs include early training, inclusion of experienced hens with new flocks, and limiting litter access. However, ground robots may provide a means to discourage floor egg laying without inducing stress in hens. Effects of ground robots on hen floor egg reduction, production performance, stress response, bone quality, and behavior were investigated in this study. It was found that the ground robots reduced floor eggs to certain degrees during the first two weeks of robot operation, but the effect diminished as birds became accustomed to the robots. The robot did not negatively affect hen-day egg production, feed intake, and feed conversion ratio. Physiological and skeletal responses, including plasma corticosterone concentrations, bone breaking force, fresh bone weight, dried bone weight, bone ash weight, and ash percentage, were similar with and without robot treatments. For the two-week robot treatments, time spent in nest boxes increased during the first two weeks of robot running but decreased and remained nearly unchanged in the following weeks. It is concluded that running ground robots in cage-free (CF) settings may not introduce detrimental effects on hen production performance, health conditions, and welfare, but may provide limited improvement on floor egg reduction.

Technical Abstract: Reducing floor eggs in cage-free (CF) housing systems is among primary concerns for egg producers. The objective of this research was to test whether operation of ground robots would reduce floor eggs. In addition, the effects of ground robots on production performance, stress response, bone quality, and behavior were also investigated. Two flocks of 180 Hy-Line Brown hens at week 34 were used, and birds in each flock were equally distributed into six CF pens. Each pen was assigned to one of the three treatments: without robot running, with one-week robot running, and with two-week robot running, yielding four replicates per treatment with the two flocks. Two phases were involved with each flock, with phase 1 (weeks 35-38) mimicking the normal scenario and phase 2 (weeks 40-43) mimicking a scenario with inadvertent restriction to nest box access. The results show that floor egg rates were reduced by 18.9% and 34.0% for the treatments with robot operations, as compared to 11.0% for the treatment without robot operation, in the first two weeks of phase 1. In phase 2, the effect of robot operation on floor egg production was not obvious. Other tested parameters, including hen-day egg production, feed intake, feed conversion ratio, live body weight, plasma corticosterone concentration, bone breaking force, and ash percentage, time spent in nest boxes, were similar among the treatments. In conclusion, ground robot operation in CF settings may help to reduce floor egg production to a certain degree for a short period after being introduced; however, such an effect diminished as hens became familiarized with the robot. Additionally, robot operation does not seem to negatively affect hen production performance and well-being.