Multi-breed investigation of pig social rank and biological rhythm based on feeding behaviors at electronic feeding stations

•The social rank is defined by NV, OTPV and FIPV.•VI30 can be used to describe the individual rank position of the group-members.•Duroc has an advantage over Yorkshire and Landrace in the social rank.•There is a biological rhythm on daily feed intake and average daily gain in pigs. We studied the biological rhythms and social behavior of domestic pigs. We sampled 874 fattening pigs represent three breeds (Duroc, Landrace and Yorkshire) at the Xinda Livestock Company Ltd., Henan, China and studied feeding behavior using electronic feeding stations (EFS). We recorded the number of visits per day (NV), occupation time per visit (OTPV), feed intake per visit (FIPV), final body weight (FW), amount of visits per day with the following visit interval being less than 30 s long (VI30), daily occupation time (DOT), daily feed intake (DFI), average daily gain (ADG) and days of daily feed intake less than 0.5 kg (DDFI0.5). The average NV, OTPV and FIPV values were used to determine the social rank of pigs in each pen. Pigs with longer OTPV, higher FIPV and fewer NV were defined as the highest social rank (HSR) pigs in the pen. Shorter OTPV, less FIPV and more NV were defined as signs of the lowest social rank (LSR) pigs. The LSR pigs had a longer DOT (4167 vs 3131 s) and more VI30 (6.2 vs 2.6) than the HSR pigs. However, no differences were observed for DFI, ADG, FW and DDFI0.5 between the HSR and LSR pigs. This social rank study across pig breeds clarified that there is breed priority on social rank. The HSR pigs were mainly Duroc and the LSR pigs were mainly Yorkshire. This suggested that Duroc is at the top of the pig social rankings. The season significantly impacted DFI and ADG (p