Damaging biting behaviors in intensively kept rearing gilts: the effect of jute sacks and relations with production characteristics.

Pigs may display biting behavior directed at pen mates, resulting in body damage such as tail wounds. We assessed the suitability of jute sacks (hung vertically at wall) to reduce biting behaviors and tail wounds in rearing gilts. Additionally, we assessed several characteristics of different types of tail biters. Tail docked rearing gilts originated from 72 litters, which were kept in partly slatted pens with jute sacks (J) or barren control pens (CON; 36 litters per treatment). Tail and ear damage were observed at weaning (4 wk) and during the weaner and rearing phase (17 J and 19 CON pens). Sow (dam) damage was also considered. Biting behaviors (tail, ear, and other) were observed during the weaner and rearing phase. Weight was recorded at birth, weaning, and end of the weaner phase and ADG was calculated from birth till weaning and from weaning till 9 wk. Furthermore, estimated breeding values for litter size, litter birth weight, back fat, and growth between birth and ∼ 105 kg, and ∼ 25 to 105 kg were determined. Jute sacks reduced tail and ear damage at weaning (both P < 0.001) and tended to reduce sow tail damage (P = 0.09). Jute sacks also reduced tail damage post-weaning (P < 0.001 to 0.03), with a 5-fold reduction of (mild) tail wounds at the age of 13 wk. Biting behaviors directed at pen mates were up to 50% lower in J pens (P < 0.001 to 0.04). Higher genotypic litter size, litter birth weight, growth, and lower back fat seemed associated with higher levels of ear or tail-biting behavior (P = 0.002 to 0.09), albeit dependent on treatment and phase. Higher phenotypic litter sizes were associated with higher levels of biting behaviors (P = 0.004-0.08). High-tail-biters and Medium-tail-biters (the latter less pronounced) stemmed from larger litters (P = 0.01 to 0.05), were heavier (P = 0.03 to 0.04), grew faster (P = 0.05 to 0.08), and displayed higher levels of all kinds of biting behavior directed to pen mates and the jute sack (P < 0.001 to 0.10) compared with non-tail-biters, the effect size dependent on treatment and phase of life. To conclude, jute sacks may profoundly reduce damaging behaviors and tail wounds in rearing gilts, probably because they partly meet the behavioral need of pigs for rooting and chewing. Furthermore, (tail) biting is associated with production level of the gilts (phenotypically and genetically), which suggests a role for breeding programs and additional research focusing on metabolic demands of (tail) biting pigs.