209 Influence of litter origin on performance and tail biting in growing-finishing pigs

Abstract Tail biting is a multifactorial phenomenon with many aspects contributing to a tail biting outbreak. Little is known about how social structures influence tail biting. Our objective was to determine if litter origin impacts growth performance and tail damage caused by biting behaviors of undocked growing-finishing pigs. Pigs were separated based on their litter origin. Three treatments (12 pens/treatment) were tested: LM = all littermates (all 7 pigs/pen were farrowed and nursed by the same sow), N = non-littermates (7 pigs/pen were farrowed and nursed by 7 different sows), and H = half-group of littermates (7 pigs/pen were farrowed and nursed by 2 sows with 3 or 4 of pigs from each sow). The study was conducted in 2 replications (6 pensּ treatment-1ּ replication-1). Within each replication growth performance, mortality, and morbidity were recorded for 12 wk until pigs reached market weight. Tail damage was evaluated using a subjective scoring system: 0 = no evidence of tail biting; 1 = evidence of chewing without visible blood; 2 = evidence of tail biting with visible blood; 3 = open wounds or abscesses with signs of infection; and 4 = partial or total loss of the tail. Tail damage was assessed weekly during the study period, and the maximal tail score (MTS) that each pig received over the entire 12 wk was recorded. The number of pigs removed and the reason for removal was recorded. Data were analyzed using the mixed procedure of SAS for performance variables with a statistical model including treatment, week, and their interaction as fixed effects, replication as a random effect, and initial body weight as a covariate. A frequency procedure with a chi-square (CMH) tested treatment effects on pigs removed and MTS. Litter origin did not affect average daily feed intake (ADFI), gain to feed ratio (G:F), or pigs removed from each treatment group (all P > 0.19; Table 1), but average daily gain (ADG) of H pigs tended to be greater than that of LM pigs (P = 0.07). Maximal tail score was influenced (P = 0.008) by litter origin treatments. Pigs in LM groups had a greater percentage of MTS 0 compared with H and N groups; and H had greater severity of tail damage with 16.7% of the pigs having an MTS of 3 or greater, while both LM and N had less than 5%. Results of this study suggest that litter origin can influence severity of tail damage caused by tail biting behaviors as indicated by MTS. Future studies should focus on the differences among litter origin treatment groups regarding social interactions to further understand how social structure influences tail biting behaviors.