Understanding tail-biting in pigs through social network analysis

Yuzhi Li, Haifeng Zhang, Lee J Johnston, Wayne Martin

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The objective of this study was to investigate the association between social structure and incidence of tail-biting in pigs. Pigs (n = 144, initial weight = 7.2 ± 1.57 kg, 4 weeks of age) were grouped based on their litter origin: littermates, non-littermates, and half-group of littermates. Six pens (8 pigs/pen) of each litter origin were studied for 6 weeks. Incidence of tail injury and growth performance were monitored. Behavior of pigs was video recorded for 6 h at 6 and 8 weeks of age. Video recordings were scanned at 10 min intervals to register pigs that were lying together (1) or not (0) in binary matrices. Half weight association index was used for social network construction. Social network analysis was performed using the UCINET software. Littermates had lower network density (0.119 vs. 0.174, p < 0.05), more absent social ties (20 vs. 12, p < 0.05), and fewer weak social ties (6 vs. 14, p < 0.05) than non-littermates, indicating that littermates might be less socially connected. Fifteen percent of littermates were identified as victimized pigs by tail-biting, and no victimized pigs were observed in other treatment groups. These results suggest that littermates might be less socially connected among themselves which may predispose them to development of tail-biting.

Original languageEnglish (US)
Article number13
Issue number1
StatePublished - Jan 15 2018

Bibliographical note

Funding Information:
Acknowledgments: This work is partially supported by Rapid Agricultural Response Funds from the Minnesota Agricultural Experimental Station.

Publisher Copyright:
© 2018 by the author. Licensee MDPI, Basel, Switzerland.


  • Pigs
  • Social network analysis
  • Tail-biting


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