Cortisol administration to pregnant sows affects novelty-induced locomotion, aggressive behaviour, and blunts gender differences in their offspring

Several behavioural effects of prenatal stress are reported in literature, and these seem to depend, among other factors, on the gender studied and the period of gestation in which prenatal stress is applied. In the present study, oral administration of hydrocortisone-acetate (HCA) to 41 pregnant sows was used as a model for prenatal stress, since corticosteroids are considered a key mediator in the effects of prenatal stress. HCA was orally administered to pregnant sows during three periods of gestation: 21-50 (period 1, P1, n = 10), 51-80 (period 2, P2, n = 10) and 81-110 (period 3, P3, n = 10) days after insemination (term 115 days). Control sows (n = 11) received vehicle from 21 to 110 days after insemination. Between days 9 and 48 after birth, treatment effects on male and female piglet behaviour were determined in the home pen and in four different behavioural tests. During the backtest, no gender differences were observed in vocalisations in HCA-piglets, while control males vocalised more than control females. In the home pen at 14 days of age, HCA-piglets spent less time in social interactions than control piglets. During the novel environment test, P1- and P3-piglets walked more than control piglets, but this was not observed during the novel object test, four days later. At weaning, P2- and P3-piglets performed less individual play. Prior to mixing with an unfamiliar piglet (male piglets only), HCA-piglets had lower salivary cortisol concentrations than control piglets, but no difference was observed after mixing. P1-, P2-, and P3- piglets had fewer non-aggressive encounters, and P2-piglets continued fighting longer than control piglets. The present study demonstrates that elevated maternal cortisol concentrations during gestation affect piglet behaviour, and effects do differ between male and female piglets. In addition, effects depend on the period of cortisol administration.     

Behavioural,endocrine and immune consequences of mixing in weaned piglets

Mixing piglets at weaning increases plasma cortisol concentrations and agonistic behaviour. In contrast to what is observed in older pigs, studies failed to show any effect of social environment on other behavioural variables or on immune function. The lack of effect of mixing may not reflect an absence of stress, but rather the fact that the physiological effects of social reorganisation are masked by the much more important effects of diet change. The aim of this experiment was to evaluate the reactivity of piglets to mixing by dissociating social reorganisation from weaning in itself. For this purpose, the influence of mixing was investigated 5 days after weaning (day 0) in eight control (C) and eight mixed (M) female pigs. Salivary cortisol and behavioural activity were measured from day −1 to day 3. Blood lymphocyte proliferation was measured on days 0 and 3. Cortisol levels were increased after mixing and returned to basal values within 24 h. Blood lymphocyte proliferation was not affected. Mixing increased resting behaviour. Cortisol and behavioural responses were influenced by the social position of individuals in their new group. Piglets seemed to avoid conflicting encounters by diminishing the synchronisation of their activities with their new group. These results suggest that social reorganisation could be stressful for weaned pigs. However, piglets seem to develop behavioural strategies, which could explain the absence of long-term endocrine and immune consequences of mixing.     

Maternal behaviour in sows of different social rank

The maternal behaviour of domestic sows in intensive husbandry has been studied in relation to their social rank during the second half of pregnancy when they were kept in groups. The sows dominant during pregnancy were more active immediately before farrowing but not after it. The low-ranking sows showed much more restlessness from the early days after farrowing and many stereotyped/redirected patterns. Those sows voluntarily interrupted nursing in the early days of lactation more often, while the dominant sows were more likely to allow piglets to suckle freely.     

Social support attenuates the adverse consequences of social deprivation stress in domestic piglets

Social deprivation is a severe stressor affecting a number of behavioral and physiological functions of gregarious species. It is assumed that, dependent upon the level of familiarity, social support given by a conspecific may attenuate the adverse consequences of stress. We investigated the effects of a 4 h maternal and littermate deprivation on behavioral reactions, stress hormone responses and brain corticosteroid receptor expression in 7-, 21- and 35-day-old domestic piglets (Sus scrofa) that were left alone or in the presence either of a familiar or unfamiliar age-matched piglet. Compared to control animals, all of the socially deprived piglets showed significant stress responses, such as impaired habituation in repeated open-field/novel-object tests, enhanced ACTH and cortisol release, and altered corticosteroid receptor expression in the hypothalamus. In addition, our results demonstrated that younger piglets had more difficulty coping with stress. The presence of an age-matched conspecific had a direct calming effect on the deprived piglet during the deprivation procedure, which was revealed by diminished stress-induced HPA activity and altered reactions in the behavioral test situations (e.g., activity, escape, and vocalization). Furthermore, because the presence of a familiar piglet causes a more pronounced buffering effect, we have shown for the first time that the degree of familiarity between the piglets may influence the effectiveness of social support. Our study emphasizes the benefits of social partners on positive welfare and the ability for pigs to cope with stress; therefore, our results should be taken into account during handling practices such as weaning and mixing.     

The maternal social environment shapes offspring growth,physiology, and behavioural phenotype in guinea pigs

Background

Prenatal conditions influence offspring development in many species. In mammals, the effects of social density have traditionally been considered a detrimental form of maternal stress. Now their potential adaptive significance is receiving greater attention.Sex-specific effects of maternal social instability on offspring in guinea pigs (Cavia aperea f. porcellus) have been interpreted as adaptations to high social densities, while the effects of low social density are unknown. Hence, we compared morphological, behavioural and physiological development between offspring born to mothers housed either individually or in groups during the second half of pregnancy.

Results

Females housed individually and females housed in groups gave birth to litters of similar size and sex-ratios, and there were no differences in birth weight. Sons of individually-housed mothers grew faster than their sisters, whereas daughters ofgroup-housed females grew faster than their brothers, primarily due to an effect on growth of daughters. There were few effects on offspring behaviour. Baseline cortisol levels in saliva of pups on day 1 and day 7 were not affected, but we saw a blunted cortisol response to social separation on day 7 in sons of individually-housed females and daughters of group-housed females. The effects were consistent across two replicate experiments.

Conclusions

The observed effects only partially support the adaptive hypothesis. Increased growth of daughters may be adaptive under high densities due to increasedfemale competition, but it is unclear why growth of sons is not increased under low social densities when males face less competition from older, dominant males. The differences in growth may be causally linked to sex-specific effects on cortisol response, although individual cortisol response and growth were not correlated, and various other mechanisms are possible. The observed sex-specific effects on early development are intriguing, yet the potential adaptive benefits and physiological mechanisms require further study.

     

A note on the effects of co-mingling piglet litters on pre-weaning growth, injuries and responses to behavioural tests

The purpose of this study was to determine how co-mingling litters affected piglets’ pre-weaning growth, ear injuries, suckling behaviour and responses to behavioural tests used to measure coping abilities. Thirty sows and their respective litters were housed in standard farrowing crates until day 13 after birth. On day13, the partition between two neighbouring pens was removed for 20 litters allowing piglets to interact (forming 10 co-mingled litters). The remaining 10 control litters were kept in standard farrowing crates throughout the experiment. Three focal piglets from each litter were used for data collection. Focal piglets were weighed and ear injuries recorded on days 2, 4, 9, 12, 15 and 18 after birth. There were no differences in piglets’ weight gain before or after co-mingling. Ear injuries were more abundant in co-mingled litters on day 15 (P < 0.05) but these differences disappeared by day 18. Suckling behaviour was recorded on days 5, 8, 10, 14, 16 and 18 after birth. There were no differences in teat fidelity, suckling frequency and mother fidelity between treatments. Three behavioural tests, social challenge, isolation, and backtest, were performed before and after co-mingling. There were no treatment effects on piglets’ response to the isolation test and backtest. Co-mingled piglets showed longer latency for the first aggressive interaction (P < 0.05), spent more time in proximity to one another (P < 0.05) and performed less single bites (P < 0.05) than control piglets during the social challenge. In addition, the duration and frequency of aggressive interactions (P < 0.05) were lower in co-mingled piglets than control piglets. Co-mingling did not affect the frequency of single head thrusts or oral–nasal contact, but did tend to increase the frequency of escape attempts (P < 0.10). Our results suggest that co-mingling litters during lactation affects piglets’ social behaviour, by primarily decreasing aggressive interactions during social challenges.     

Influence of Litter Gender Composition on Subsequent Maternal Behaviour and Maternal Aggression in Female House Mice

It has been suggested that the sex-dependent pattern of mother-pup interaction that occurs early in infancy can affect some aspects of the animal's behaviour repertoire in adulthood. The aim of this study was to investigate the effects of litter gender composition (LGC) on subsequent maternal behaviour and aggression in the female house mouse. Albino mouse litters were reduced at birth to six pups according to two conditions: FM (3 females and 3 males) and FF (all females). At weaning (day 21), all mice were rehoused in unisexual groups. At adulthood (70–90 days) the females were mated and litters culled at birth to 6 pups (3 females and 3 males). On days 2, 4, and 6 after delivery the females were tested for maternal behaviour (10 min) and retrieval of pups. On day 6, at the end of the recording of maternal behaviour, the females were also tested for maternal aggression towards a strange adult male conspecific (5-min exposure). In absence of differences in maternal behaviour scores, FM females showed shorter latencies for retrieval of the first pup on postnatal days 2 and 4. Maternal aggression was also significantly affected by the two conditions. FM females showed higher scores of both duration and frequency of aggressive grooming, defensive upright postures, fleeing and of the number of attacks. FF females spent more time self-grooming, crouching, and on nest. These results support the hypothesis that a series of factors, such as olfactory, tactile, and acoustic stimulation provided by the pups, the variation of maternal behaviour depending upon LGC, and the qualitative and/or quantitative variation in social interaction with the opposite sex in infancy, contribute to the broad interindividual plasticity to cope in different environmental situations.     

Impact of social stress during gestation and environmental enrichment during lactation on the maternal behavior of sows

The impact of a social stress in gestation and an enriched pen in lactation on components of sow maternal behavior was studied in a 2 × 2 factorial experiment. At breeding, 41 sows were assigned to a social mixing stress treatment (T) during mid-gestation or a control group (C). During lactation, half of the T and C sows were housed in straw enriched pens (E) (1.57 m × 4.10 m) and the others in standard farrowing crates (S) (0.68 m × 2.10 m). The mixing stress consisted in introducing each T sow to the home pen of two unfamiliar sows twice for 1 week, from d 39 to 45 and 59 to 65 of gestation. Aggressive behavior was observed and lesion scores were taken to confirm that a social stress occurred. During lactation, the responses of sows to a simulated piglet crush test on d 3 and an isolated piglet playback test on d 21 were observed. Postural budgets of sows were automatically detected using accelerometers on d 5 and 19 of lactation. Sow-initiated social contacts with the piglets were observed continuously from video recordings on d 6 and 20 of lactation. Data were analyzed with a mixed models procedure. The social stress treatment had an impact on the response of sows to isolated piglet vocalizations with T sows showing longer latencies to respond vocally than C sows (P = 0.035). In early lactation, T sows spent more time lying ventrally than C sows (P = 0.007). Furthermore, the social stress had an impact on the space use in the enriched housing, with T sows spending less time in the nesting straw area of the pen than C sows (P = 0.018). Housing also impacted maternal behavior with E sows tending to spend more time lying ventrally than S sows in late lactation (P = 0.067) and tending to have more social contacts with their piglets than S sows in early lactation (P = 0.058). In conclusion, the social stress during gestation had a slight negative impact on sow maternal behavior, and while an enriched farrowing pen allowed for more opportunities to express maternal behavior, it did not counteract the negative effects of gestation stress.     

Effect of gradual transition from maternal to reconstituted milk on behavioural,endocrine and immune responses of lambs

The possibility of reducing the stress associated with artificial rearing through a gradual transition from maternal to reconstituted milk was assessed in thirty Comisana lambs. Animals were assigned to a control dam-suckled group (Suckled) and two test groups. Eighteen to twenty-four hours after parturition, test lambs were separated from their dams: 10 subjects were offered a commercial milk substitute (Sub), whereas the other ten (Mix) were subjected to a gradual transition from maternal to reconstituted milk over ten days. Test-lambs had free access to milk 3 h a day. In vivo cell-mediated immune response of lambs to phytohemagglutinin percutaneous injection was evaluated at 5, 15 and 25 days of age. At 10 and 20 days of age, all lambs were subjected to 15 min isolation tests, during which latency time to move, duration of movement and number of bleats were recorded. Blood samples were collected immediately before the test, 15 and 60 min after in order to assess the effect of differential rearing on cortisol response of animals at different ages. In addition, weight gains of all lambs and milk intakes of test lambs were recorded during the first 35 days of age at weekly intervals. Sub showed a lower immune response (P<0.01) and, at 10 days of age, increased levels of plasma cortisol (P<0.001) as well as a reduced duration of movement (P<0.001) and a longer latency time to move (P<0.001) compared to Suckled and Mix. There were no significant differences between Suckled and Mix for both immune, cortisol and behavioural responses. Mix lambs consumed more milk (P<0.006) and had higher weight gains (P<0.001) compared to Sub lambs. However, Mix lambs gained less weight on average (P<0.05) than Suckled lambs. Our results suggest that a gradual transition from maternal to reconstituted milk is effective in stimulating milk consumption and minimising the detrimental effects of artificial rearing on behavioural, endocrine and immune responses of lambs.     

Effects of season on the behaviour of early-weaned piglets during and immediately following transport

In North America commercial transport of piglets occurs without supplemental heat, over long durations (24 h) and without feed and water. Scan sampling was used to compare behaviour across seasons (summer, fall, winter) and over representative durations (Control, 6, 12 or 24 h) to help assess welfare. Six groups of 48 Cotswold piglets (17 ± 1 d) were weaned and transported along highways in a van equipped for video and temperature recording. Following transport, piglets were studied in groups of four, in weanling pens with free choice feed and water. Resting during transport increased in frequency from 59.8% (1–12 h) to 91.5% (13–24 h). This pattern was more defined in winter and fall implicating cold as a causal factor. Fatigue, as observed in slaughter hogs, may also be a factor. Higher levels of post-transport resting in transported (81.4%) compared to control piglets (77.5%) supported this interpretation. Habituation to transport conditions may also have affected behaviour as piglet interactions commonly associated with dominance hierarchy establishment, were more frequent, and sitting, a behaviour associated with stress post-weaning decreased in the last 12 h of transport. As the duration of transport increased, post-transport drinking frequency increased, although significance was reached between control (2.4%) and 24 h of transport (3.7%) only. Long transport durations may thus delay hierarchy development, require additional coping strategies with respect to cold and increase the risk for dehydration. However, indications for habituation to some aspects of transport after 12 h are also apparent. During winter transport the frequency of piglet interactions (three piglets) was much lower than in summer (39 piglets) and fall (18 piglets) indicating that the cold temperatures may have affected establishment of a dominance hierarchy. Summer and winter transport differed from fall transport, with less resting (5.5% versus 9.2%) and standing (5.5% versus 9.25%), and more sitting (0.52% versus 0.28%) during the fall, a pattern consistent with increased stress during fall transport. Higher levels of resting for 3 days in winter and 2 days in summer could indicate more post-transport fatigue in these seasons. Transport, irrespective of season, resulted in behaviour indicative of coping strategies. It is important to determine which stressors have the greatest impact in each season and develop strategies to reduce the effects of transport on welfare.