• Post-mortem examination was performed in 798 piglets from 363 litters.
• The major post-mortem findings were starvation (34%) and crushing (28%).
• Fewer piglets starved to death in STRAW compared to CONTROL-litters.
• Strategic use of straw reduced the number of stillborn piglets by 27%.
Piglet survival is the outcome of complex interactions between the sow, the piglet and
their environment. In order to facilitate nest-building and to provide a suitable environment for the newborn piglets, a strategic method to supply loose housed sows with large quantities of straw at farrowing has been developed by Swedish piglet-producing farmers. The objectives of this cohort study were to use post-mortem findings to assess the causes of death and to quantify the effect of a large quantity of straw provided before farrowing compared to limited small daily amounts on stillbirths, post-mortem findings in piglets dying within 5 days after birth and the pre-weaning mortality. On each of four commercial piglet-producing farms in South-West Sweden, one batch of sows was studied during two consecutive lactations. At inclusion, sows were randomly assigned to two treatment groups, and sows remaining in the batch during the next lactation switched treatment group. In the STRAW group (n = 181 litters) sows were provided with 15–20 kg of chopped straw 2 days prior to the calculated date of farrowing. Sows in the CONTROL group (n = 182 litters) received 0.5–1 kg of chopped straw on a daily basis plus about 2 kg for nest-building when the stockperson judged the sow to be about to farrow. After onset of farrowing, additionally 1–2 kg was given. Post-mortem examination was performed in all piglets that died within 5 days after birth (n = 798). The three major post-mortem findings were starvation (34%) crushing by the sow (28%), and enteritis (24%). In conclusion, strategic use of large quantities of straw reduced the number of stillborn piglets per litter by 27% (p = 0.007). Under the conditions studied, the pre-weaning mortality of liveborn piglets was not affected by treatment; however, the distribution of post-mortem findings differed with fewer piglets dying due to starvation and more due to crushing and enteritis in STRAW litters.
• Nest building behaviour and farrowing duration were studied in 138 sows.
• A large quantity (15–20 kg) of straw given once was compared to small daily amounts.
• Time spent nest building during 18 h pre-partum was increased by 19%.
• A 1-h increase in time spent nest building reduced the farrowing duration by 12%.
In spite of domestication, sows are still genetically programmed to perform nestingbehaviour close to farrowing. In order to facilitate nest building, a method for a strategic useof large quantities of straw has been developed by Swedish piglet producing farmers. Theobjectives of the present study were to quantify the effect of strategic use of 15–20 kgof chopped straw given once 2 days prior to expected date of farrowing, compared tosmall daily amounts (0.5–1 kg) and 2 kg close to farrowing (controls), on the nest buildingbehaviour and the duration of farrowing. The behaviour from 18 h pre-partum until 1 h afterbirth of first piglet and the duration of farrowing was continuously observed in 138 videorecordings from 4 commercial farms. On each farm, 20–34 sows (parity ≥ 2) were stud-ied during one or two consecutive lactations. Compared to controls, strategic use of strawtriggered the sows to start nest building earlier and increased the total time spent nestbuilding pre-partum by 19% (p = 0.039). Sows given large amounts of straw also performedless nesting behaviours during the first hour after birth of the first piglet. This shows thatnest building is affected not only by the presence of straw, but also by the quantity of strawprovided, and that 2 kg of chopped straw seems to be too little to make the sow terminatenest building well in advance of farrowing. There was no significant effect of treatment onthe duration of farrowing but a strong negative association was found between time spentnest building pre-partum and the duration of farrowing regardless of treatment. The modelpredicted a 1-h increase in total nest building time pre-partum to be associated with a 12%(95% CI = 4–19%) shorter duration of farrowing (p = 0.004).
With the increase in attention to animal welfare, researchers have focused their interest on the assessment of pain in farm animals. In humans who cannot self-report, such as infants and unconscious patients, the observation of facial expression is frequently used for pain assessment (Prkachin, 2009). The possibility to assess pain through changes of facial expression has also been studied in animals, and pain scales developed which include the ‘Mouse Grimace Scale’ (Langford et al., 2010), the ‘Rat Grimace Scale’ (Sotocinal et al., 2011) and the ‘Rabbit Grimace Scale’ (Keating et al., 2012). Although with some species differences, the three scales focus on the eyes, nose, cheeks, ears and whiskers of an animal.
Although pigs have fewer muscles for facial expression, there are subtle changes in appearance (Flecknell & Watermann-Pearson 2000), but there are currently no published pain scales based on facial expression in pigs. The aim of this research was to investigate if it is possible to observe changes in piglets’ facial expressions immediately after painful procedures. Thirty-one piglets were subjected to tail docking by cautery, while held by the farmer. Images of faces were taken immediately before and after this procedure. These images were sorted and those in which piglets had closed eyes were excluded.
Images were evaluated by two treatment-blind observers, scoring from 0 to 2 (0 was no evident tension and 2 very evident tension).
Because of the non normal distribution, data were analysed with the non-parametric Wilcoxon Signed Rank Test, which showed that the cheek tension score significantly increased from before to after the procedure (P<0.042). This result shows promise for the adoption facial expression as a tool for acute pain assessment in pigs.
In piglets subjected to tail docking cheek tension score significantly increased from before to after the procedure (P<0.05)
A recent paper by Valros et al. (2015) shows evidence for changes in monoamine metabolism in the brains of pigs affected by tail biting, both in the victims and the biting pigs.
Tail biting in pigs is a major welfare problem within the swine industry. Even though there is plenty of information on housing and management-related risk factors, the biological bases of this behavioral problem are poorly understood. The aim of this study was to investigate a possible link between tail biting, based on behavioral recordings of pigs during an ongoing outbreak, and certain neurotransmitters in different brain regions of these pigs. We used a total of 33 pigs at a farm with a long-standing problem of tail biting. Three equally big behavioral phenotypic groups, balanced for gender and age were selected, the data thus consisting of 11 trios of pigs. Two of the pigs in each trio originated from the same pen: one tail biter (TB) and one tail biting victim (V). A control (C) pig was selected from a pen without significant tail biting in the same farm room. We found an effect of tail biting behavioral phenotype on the metabolism of serotonin and dopamine, with a tendency for a higher 5-HIAA level in the prefrontal cortex (PFC) of TB compared to the other groups, while V pigs showed changes in both serotonin and dopamine metabolism in the striatum (ST) and limbic cortex (LC). Trp:BCAA and Trp:LNAA correlated positivelywith serotonin and 5-HIAA in the PFC, but only in TB pigs. Furthermore, in both ST and LC, several of the neurotransmitters and their metabolites correlated positively with the frequency of bites received by the pig. This is the first study indicating a link between brain neurotransmission and tail biting behavior in pigs with TB pigs showing a tendency for increased PFC serotonin metabolism and V pigs showing several changes in central dopamine and serotonin metabolism in their ST and LC, possibly due to the acute stress caused by being bitten.
Reference: Valros, A., Palander, P., Heinonen, M., Munsterhjelm, C., Brunberg, E., Keeling, L., & Piepponen, P. (2015). Evidence for a link between tail biting and central monoamine metabolism in pigs (Sus scrofa domestica). Physiology & Behavior.