Inger Lise Andersen

The effects of weight asymmetry and resource distribution on aggression in groups of unacquainted pigs

The relationship between weight asymmetry and aggression when mixing groups of unacquainted pigs in two different environments was investigated. Ten groups of 4 female (LandracexYorkshire), unacquainted pigs with a weight asymmetry of 3.1+/-0.2 kg (mean weight: 16.6+/-0.6 kg) between each pig, and another 10 groups with a weight asymmetry of 1.2+/-0.1 kg (mean weight: 14.1+/-0.1 kg), were mixed at the age of 7 weeks. Ten of the groups (five of each) were mixed in an experimental pen with a heterogeneous distribution of straw. The pen consisted of two main compartments with straw in one of them, and a passage area with concrete floor in between. The other 10 groups were mixed in the same pen, but with a homogenous distribution of straw (straw spread all over the pen).The results showed that fighting duration was significantly shorter in groups with large weight asymmetry than in groups with small weight asymmetry irrespective of the environment. The number of bites delivered during the fights in the heterogeneous environment was lower in groups with large weight asymmetry than in groups with small weight asymmetry. In the homogenous environment, however, there was no significant difference between groups with large and small weight asymmetries regarding the number of bites. The combination of a limited straw area and a small weight asymmetry resulted in the greatest number of bites. In groups with large weight asymmetry, the largest pig won around 50% of the fights, and 25% of the variation in the percentage of fights won was explained by the weight asymmetry.In groups with small weight asymmetry, less than 10% of the variation in the percentage of fights won could be explained by weight asymmetry. The two largest pigs delivered significantly more bites and spent significantly more time fighting than the smallest pig. The second largest pig received significantly more bites and body lesions than the smallest pig in the groups. Fights between the two largest pigs had a significantly longer duration than when other pigs were involved. The results were discussed in relation to sequential assessment theory and resource defence theory.

Maternal investment, sibling competition, and offspring survival with increasing litter size and parity in pigs (Sus scrofa)

The aim of this study was to examine the effects of litter size and parity on sibling competition, piglet survival, and weight gain. It was predicted that competition for teats would increase with increasing litter size, resulting in a higher mortality due to maternal infanticide (i.e., crushing) and starvation, thus keeping the number of surviving piglets constant. We predicted negative effects on weight gain with increasing litter size. Based on maternal investment theory, we also predicted that piglet mortality would be higher for litters born late in a sows life and thus that the number of surviving piglets would be higher in early litters. As predicted, piglet mortality increased with increasing litter size both due to an increased proportion of crushed piglets, where most of them failed in the teat competition, and due to starvation caused by increased sibling competition, resulting in a constant number of survivors. Piglet weight at day 1 and growth until weaning also declined with increasing litter size. Sows in parity four had higher piglet mortality due to starvation, but the number of surviving piglets was not affected by parity. In conclusion, piglet mortality caused by maternal crushing of piglets, many of which had no teat success, and starvation caused by sibling competition, increased with increasing litter size for most sow parities. The constant number of surviving piglets at the time of weaning suggests that 10 to 11 piglets could be close to the upper limit that the domestic sow is capable of taking care of.

The influence of different feeding arrangements and food type on competition at feeding in pregnant sows

Abstract The effects of different feeding arrangements (body, shoulder and no partitions between sows) and type of food (wet vs. dry) on aggressive competition at feeding were investigated. Six groups of six pregnant sows were subjected to all the six treatments, and the order of treatments were rotated systematically. In the last 2 days of each treatment period (lasting for 9 days in total), the behaviour of the sows was video recorded for 60 min from the start of feeding. Aggressive behaviours (bite towards head/shoulder and body, bite towards vulva, push, threat, head knock), frequency of changing position at the trough (displacements and voluntary changes of position) and the time at trough were recorded. In the analysis, the observation period was divided into feeding (0–15) and post feeding (45–60 min). On dry feeding, increasing length of partitions resulted in a significant reduction in the number of bites, total aggressive behaviours and displacements at the trough and an increased time at trough. The number of bites and total aggressive behaviours were lower on wet than on dry feeding in the simple feeding arrangements (i.e., shoulder or no partitions), but there were no significant differences when body partitions were used. On wet feeding, there were no significant differences between body and shoulder partitions concerning the number of bites, nor were there any significant differences between feeding arrangements concerning the time at trough or the number of displacements at trough when wet food was used. The top ranked sows received less bites and displacements and spent more time at trough than the other sows in all feeding arrangements, whereas the lower ranked sows were less subjected to aggression and displacements and spent more time at the trough as the length of partitions increased. In conclusion, a feeding arrangement with body partitions resulted in the least aggression and displacements at trough compared to a situation with shoulder or no partitions. On wet feeding, however, the amount of aggression did not differ between shoulder and body partitions, and the time at trough appeared to be almost equal in all feeding arrangements. Simple feeding systems may thus be used without increasing the amount of aggression or reducing the eating time when wet food is used. However, the differences in eating time, aggression received and displacements between sows of different rank order will increase with decreasing length of partitions at the trough, and in a situation without partitions the low-ranking individuals may suffer from a reduced food intake. Body partitions is therefore still a more recommendable feeding system.

INVITED REVIEW: Piglet mortality: Management solutions

Preweaning mortality varies greatly among herds and this is partly attributed to differences in farrowing house management. In this review, we describe the various management strategies than can be adopted to decrease mortality and critically examine the evidence that exists to support their use. First, we consider which management procedures are effective against specific causes of death: intrapartum stillbirth, hypothermia, starvation, disease, crushing, and savaging. The most effective techniques include intervention to assist dystocic sows, measures to prevent and treat sow hypogalactia, good farrowing house hygiene, providing newborn piglets with a warm microenvironment, early fostering of supernumerary piglets, methods that assist small and weak piglets to breathe and obtain colostrum, and intervention to prevent deaths from crushing and savaging. The provision of nest-building material and modifications to the pen to assist the sow when lying down may also be beneficial, but the evidence is less clear. Because most deaths occur around the time of farrowing and during the first few days of life, the periparturient period is a particularly important time for management interventions intended to reduce piglet mortality. A number of procedures require a stockperson to be present during and immediately after farrowing. Second, we consider the benefits of farrowing supervision for preweaning mortality in general, focusing particularly on methods for the treatment of dystocia and programs of piglet care that combine multiple procedures. Third, we discuss the need for good stockmanship if farrowing supervision is to be effective. Stockmanship refers not only to technical skills but also to the manner in which sows are handled because this influences their fearfulness of humans. We conclude that piglet survival can be improved by a range of management procedures, many of which occur in the perinatal period and require the supervision of farrowing by trained staff. Although this incurs additional labor costs, there is some evidence that this can be economically offset by improved piglet survival.

Relationship between postnatal piglet mortality, environmental factors and management around farrowing in herds with loose-housed, lactating sows

Abstract The objective of this study was to investigate management routines and environmental factors influencing postnatal piglet mortality in commercial herds with individually loose-housed sows. Last year production records from 39 herds were used. We gathered information on specific routines as well as environmental factors by visiting every farm once. Herds practising moderate roughage feeding during pregnancy tended to have lower piglet mortality (p=0.06). Use of farrowing rails along all the sides of the pen resulted in lower piglet mortality than when no rails were present (p<0.01). Herds that hardly used any litter in the sow area at the time of farrowing had significantly higher piglet mortality than herds that used a moderate or large amount (p<0.05). Helping the piglets to obtain colostrum immediately after birth also reduced mortality (p<0.05), whereas other routines such as shutting the piglets inside the creep area while feeding the sow did not have any significant effect.

Drying and warming immediately after birth may reduce piglet mortality in loose-housed sows

The aim of the present experiment was to investigate the effects of placing newborn piglets under the heat lamp or both drying and placing them under the heat lamp on piglet mortality. Sixty-seven healthy (Landrace × Yorkshire) sows were divided equally into three different experimental groups: a control group where the farrowings occurred without supervision from the farmer (C; n = 23 litters), another group where the piglets were placed under the heat lamp in the creep area immediately after birth (HL; n = 22 litters) and a third group where the piglets were dried with straw and paper towels followed by placing them under the heat lamp in the creep area immediately after birth (DHL; n = 22 litters). The sows were individually loose-housed in farrowing pens during farrowing and lactation. The piglets were not closed inside the creep area, but were free to move around in the pen. The routines in the experimental groups required the stock person to attend the farrowings from the onset of birth of the first piglet until the last piglet was born. All the dead piglets were weighed and subjected to a post mortem examination at the farm to ascertain the causes of death. Postnatal mortality (% of live born) was significantly lower in the HL and DHL groups than in the control group (P < 0.0001). This was significant concerning all causes of mortality. Compared to the control group, crushing occurred in significantly fewer litters when the piglets were both dried and placed under the heat lamp (P < 0.05). In the DHL treatment, crushing of one or more piglets by the sow occurred in only 13.6% of the litters, whereas this was increased to 34.8% in the HL and to 47.9% in the control group, respectively. All causes of death, except the proportion of stillborn piglets, increased significantly with increasing litter size. Because of the relatively large potential that these rather simple routines may have to improve piglet survival, different types of management or human interference around the time of farrowing should be compared on a larger scale, both experimentally and on commercial farms.

Factor analysis of behaviour in the porcine and murine elevated plus-maze models of anxiety

Abstract The elevated plus-maze, a widely used and well-validated test for studying anxiety-related behaviour in rodents, has recently been suggested for studying anxiety- or fear-related behaviour in swine. There are, however, clear evolutionary, and thus behavioural differences, between these two species. The aim of the present experiment was therefore to compare the behaviour of mice and swine in the murine and porcine elevated plus-maze (PEPM), respectively. To analyse the behaviour of swine, a database including 84 naive weaned pigs was used, while the analysis of mouse behaviour was based on a database of 79 naive individuals. Plus-maze behaviour of the two species was compared on the basis of factor analysis. Based on the hypothesis that the elevated plus-maze induces behaviour related to anxiety in pigs, as well as in mice, it was predicted that factor analysis of pig behaviour should produce factor loadings similar to those found for mice. More specifically, elements predicted to be anxiety-related for pigs (percent open entries, open arm time, percent open arm time) should load highly and independently on a single factor. Furthermore, elements predicted to be activity-related (closed entries and total entries) should also load highly and independently on a separate factor. The orthogonal factor pattern confirmed these predictions. On the other hand, pigs did not express the unconditioned avoidance of open arms observed for mice. It is therefore concluded that the present data provide only equivocal support for the validity of the PEPM.

Piglet use of the creep area and piglet mortality – effects of closing the piglets inside the creep area during sow feeding time in pens for individually loose-housed sows

The aim of this study was to investigate the effects of closing the piglets inside the piglet creep area during the first two or four sow feedings on piglet mortality from birth until weaning and piglet use of the creep area within the first 3 days after farrowing. A total of 96 sows in individual loose-housing farrowing pens were randomly allotted to one out of three groups: C0 – control (piglets not closed inside the creep area during feeding), C2 – piglets closed inside the creep area during the first two sow feedings after farrowing, C4 – piglets closed inside the creep area during the first four sow feedings after farrowing. Production results were registered on all sows, and the behaviour of 33 of the sows and litters were recorded, using instantaneous sampling every 10 min for 6 h during day 1, 2 and 3 after farrowing (farrowing=day 0). There were no effects of closing the piglets inside the creep area during sow feeding on piglet mortality, piglet activity or location. However, to make this conclusion reliable, this should be tested for several herds and with different types of creep areas. The piglets were lying increasingly more in the creep area from day 1 to day 3 ( P P P

Behavioural and physiolgical thermoregulation in groups of pregnant sows housed in a kennel system at low temperatures

The behavioural and physiological responses of pregnant sows to cold exposure in a kennel system were investigated. Ten groups, each of six pregnant sows, were housed over winter in a non-insulated building containing kennels. Lying posture, social thermoregulation, time spent inside the kennels and general activity were recorded in three 48-h periods with different diurnal room temperatures: cold (−9 to −1 °C), medium (0 to +3 °C) and warm (+4 to +9 °C). Blood samples were collected from two of the groups, and the concentrations of glucose, free fatty acids, total thyroxine (TT4) and free thyroxine (FT4) in the plasma were determined.The air temperature difference in between the surrounding room and the kennels increased with decreasing room temperature with a maximum of 12 °C at a room temperature of −10 °C. Activity level did not differ significantly between temperature periods (30.6 ± 1.1%). At all temperature periods, the sows spent between 80 and 90% of their time inside the kennels. The sows spent ...

No effect of variation in handling on behaviour in a porcine elevated plus-maze - a brief report.

The elevated plus-maze is a widely used model of anxiety in rodents and has recently been suggested as a putative model of anxiety or fear in swine. The aim of the present experiment was to examine the effects of a pretest blood sampling procedure on the behaviour of weaned pigs in an elevated plus-maze. Animals in the control group were lifted one-by-one into a transport trolley and moved to the test apparatus, where they were observed for a 5-min period. The treatment group differed from the control group in that these animals were immobilized with a nose snare and a blood sample was extracted from the jugular vein prior to transport to the test room. Behaviour in the porcine elevated plus-maze did not differ significantly between the two handling procedures.