Stress measures in tail biters and bitten pigs in a matched case-control study

Abstract

This study aimed to identify differences in stress measures in pigs (Sus scrofa) with different roles during a tail-biting outbreak. Quartets (n = 16) of age-and gender-matched fattening pigs including a tail biter (TB; n = 16), a victim (V; n = 16), a control in the same pen (C tb ; n = 10), and one in a pen without tail biting (C no ; n = 14) were chosen by direct behavioural observation. Stress measures used were behaviour (dog-sitting, sniffing of pen-mates and aggression), thyroid hormone concentration, morphology of adrenal and thyroid glands and salivary cortisol concentration sampled at 0700, 1000, 1600 and 1900h. Category (TB, V, C tb , C no ) effects were investigated using a mixed model with replicate as subject and category as repeated effect. Category had a significant effect on adrenal total (cortex + medulla) and cortical area, salivary cortisol at 1900h, serum triiodothyronine (T3) and the behaviours performing and receiving sniffing. Victims suffered from a triad of chronic stress, pathology and suppressed T3 secretion. Evidence for stress in tail biters, a possible cause of the behaviour, consisted of a slightly flattened day-time cortisol pattern and more performed sniffing than all other categories. Differences in evening cortisol concentration and T3 levels between the categories in the pen with ongoing tail biting emphasise the qualities of the control animal. It supports the view that neutral pigs represent a phenotype that adopts a coping strategy leading to lower stress levels than in tail biters and victims, despite being housed in the same pen.

Injurious tail biting in pigs: how can it be controlled in existing systems without tail docking?

“…It is a considerable animal welfare (Munsterhjelm et al, 2013) and economic problem, causing painful injuries which are a site for further infection (Sihvo et al, 2012), resulting in carcass losses for producers (Valros et al, 2004;Kritas and Morrison, 2007) and reducing weight gain (Wallgren and Lindahl, 1996;Sinisalo et al, 2012). Several risk factors have been proposed, suggesting multi-factorial causation (Schrøder-Petersen and Simonsen, 2001;EFSA, 2007) and three different aetiologies have been proposed (Taylor et al, 2010).…”

The effect of ketoprofen on feeding behavior of tail-bitten pigs

“…Tail-bitten pigs have high levels of stress and there are many stressors involved in a tail-biting outbreak [22,23]. Chronic stress might lead to excess consumption of food and increased obesity, as was reported in humans [24] and rats [25].…”

Evidence for a link between tail biting and central monoamine metabolism in pigs (Sus scrofa domestica)

“…Sedation was done with an intramuscular injection of midazolam (0.5 mg/kg estimated liveweight, LW), butorphanol (0.2 mg/kg LW) and ketamine (10 mg/kg LW) and then carried to a separate room where they were euthanized with an intracardial injection of pentobarbital (20 mg/kg LW). The protocol is described in more detail by Munsterhjelm et al [3]. As there is a risk for the sedation protocol to affect the neurotransmitters and their metabolism, we tested for possible differences in duration from sedation until death between different phenotypic groups.…”

“…Chronic and/or acute stress is assumed to be the main underlying factor behind the development of tail biting. As tail biting is known to induce stress in the victims [3,30], we hypothesized that both pigs performing tail biting and victims of tail biting should show changes in central monoamine levels and metabolism.…”

“…Under suboptimal housing and management conditions, pigs are prone to start biting each other's tails, causing wounds, amputation of the tail, and infections [1,2]. Tail biting is thus a serious animal welfare problem, indicating an underlying welfare problem, and causing additional stress to the victim [3] as well as production losses due to increased need for medication, reduced growth and increased prevalence of carcass condemnation of affected pigs [4,2,5].…”