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Understanding the relationships between social stress and the gastrointestinal microbiota, and how they influence host health and performance is expected to have many scientific and commercial implementations in different species, including identification and improvement of challenges to animal welfare and health. In particular, the study of the stress impact on the gastrointestinal microbiota of pigs may be of interest as a model for human health. A porcine stress model based on repeated regrouping and reduced space allowance during the last 4 weeks of the finishing period was developed to identify stress-induced changes in the gut microbiome composition. The application of the porcine stress model resulted in a significant increase in salivary cortisol concentration over the course of the trial and decreased growth performance and appetite. The applied social stress resulted in 32 bacteria being either enriched (13) or depleted (19) in the intestine and feces. Fecal samples showed a greater number of microbial genera influenced by stress than caecum or colon samples. Our trial revealed that the opportunistic pathogens Treponema and Clostridium were enriched in colonic and fecal samples from stressed pigs. Additionally, genera such as Streptococcus, Parabacteroides, Desulfovibrio, Terrisporobacter, Marvinbryantia, and Romboutsia were found to be enriched in response to social stress. In contrast, the genera Prevotella, Faecalibacterium, Butyricicoccus, Dialister, Alloprevotella, Megasphaera, and Mitsuokella were depleted. These depleted bacteria are of great interest because they synthesize metabolites [e.g., short-chain fatty acids (SCFA), in particular, butyrate] showing beneficial health benefits due to inhibitory effects on pathogenic bacteria in different animal species. Of particular interest are Dialister and Faecalibacterium, as their depletion was identified in a human study to be associated with inferior quality of life and depression. We also revealed that some pigs were more susceptible to pathogens as indicated by large enrichments of opportunistic pathogens of Clostridium, Treponema, Streptococcus and Campylobacter. Generally, our results provide further evidence for the microbiota-gut-brain axis as indicated by an increase in cortisol concentration due to social stress regulated by the hypothalamic–pituitary–adrenal axis, and a change in microbiota composition, particularly of bacteria known to be associated with pathogenicity and mental health diseases.

Abstract Background Postnatal piglet survival is important both in economic and animal welfare terms. It is influenced by the piglet’s own direct genetic effects and by maternal genetic effects of the dam, associated with milk production and mothering abilities. These genetic effects might be correlated, affected by other non-genetic factors and unfavourably associated with other reproduction traits such as litter size, which makes the development of optimal breeding strategies a challenge. To identify the optimum selection strategy for piglet survival, a selection experiment was carried out to compare responses in survival and reproduction traits to selection on only direct, only maternal, or both genetic effects of postnatal survival. The data of the experiment were recorded from outdoor reared pigs, with first- and second-generation sires selected based on their estimated breeding values for maternal and direct effects of postnatal survival of indoor reared offspring, respectively, with the opportunity to identify potential genotype-by-environment interaction. Results A Bayesian multivariate threshold-linear model that was fitted to data on 22,483 piglets resulted in significant (Pr(h2 > 0) = 1.00) estimates of maternal and direct heritabilities between 0.12 and 0.18 for survival traits and between 0.29 and 0.36 for birth weight, respectively. Selection for direct genetic effects resulted in direct and maternal responses in postnatal survival of 1.11% ± 0.17 and − 0.49% ± 0.10, respectively, while selection for maternal genetic effects led to greater direct and maternal responses, of 5.20% ± 0.34 and 1.29% ± 0.20, respectively, in part due to unintentional within-litter selection. Selection for both direct and maternal effects revealed a significant lower direct response (− 1.04% ± 0.12) in comparison to its expected response from single-effect selection, caused by interactions between direct and maternal effects. Conclusions Selection successfully improved post- and perinatal survival and birth weight, which indicates that they are genetically determined and that genotype-by-environment interactions between outdoor (experimental data) and indoor (selection data) housed pigs were not important for these traits. A substantially increased overall (direct plus maternal) response was obtained using selection for maternal versus direct or both direct and maternal effects, suggesting that the maternal genetic effects are the main limiting factor for improving piglet survival on which selection pressure should be emphasized.

This paper focuses on the recent developments achieved in our group in the field of flexible polymer chain dynamics in elongational flow. Stress-induced orientation and deformation in flowing polymer solution is being surveyed in a wide variety of manifestations. Two types of flow fields have been investigated: the opposite-jet flow with a stagnation point, and the abrupt contraction flow with open flowlines. Emphasis has been placed on the latter geometry due to its widespread occurrence. Degradation experiments performed with dilute PS solutions in abrupt contraction flow demonstrate a distinct propensity for midchain scission, a feature apparently consistent with highly extended chains. On the other hand, the critical strain-rate for chain fracture (?f) determined under the same experimental conditions scales with M?1. The inverse relationship with polymer MW is characteristic of partly uncoiled chains but not of highly extended chains, for which a stronger MW dependence (?f) ? M?2 is expected. The 'yo-yo' model, which could rationalize these findings, is refuted by fluorescence depolarisation measurements which indicated that central orientation is more progressive than the average segmental orientation. For the first time, polarization-modulated birefringence was used to determine the state of local chain orientation in abrupt contraction flow. Axisymmetric contraction flow is complicated by the large variations in local molecular orientation along different streamlines. To account for this effect, a numerical inverse Abel transform has been devised to compute local birefringence (?n) from experimental retardation (?). Results show a steep decrease in birefringence with axial distance. Birefringence profiles determined in a direction perpendicular to the flow show a maximum, not at the centre, but in the vicinity of the orifice walls. This observation is in accord with flow simulation results which indicated the presence of extreme strain rates near re-entrant corners. Molecular extension ratios calculated with the Kuhn-Grün theory gives a qualitative description of polymer uncoiling up to about one third of the chain contour length at the approach of capillary entrance. A notable departure from the affine deformation model is, however, observed with multiple birefringence saturation levels changing with flow rate conditions. This behaviour could be explained by the presence of transient molecular conformations. Efforts are underway to visualize these metastable states by single chain fluorescence video microscopy using UHMW polystyrene randomly grafted with anthracene chromophores.

Because of the unequal reactivity of the two amine groups of l-lysine hydrochloride, thermal polymerization of this asymmetrical AB2monomer results in hyperbranched polymers, which contain ∼2.5 times more N-linked linear compared to N-linked linear structural units. This report discusses the feasibility of three approaches to control polymer architecture during the thermal hyperbranched polymerization of l-lysine hydrochloride. The reactivity of the more reactive -NH2group was modulated by introducing temporary protective groups that preferentially block the -NH2position. This was achieved by (i) addition of o-vanillin to the polymerization, (ii) copolymerization of N-benzylidene-l-lysine, and (iii) copolymerization of -amino--caprolactam. Analysis of the degree of branching (DB) and the average number of branches (ANB) of the obtained polymers did not provide evidence for any significant structural changes. Analysis of the distribution of structural units, in contrast, revealed major structural changes and indicated a rearrangement from N-linked linear structural units to N-linked linear structural units upon addition of o-vanillin and N-benzylidene-l-lysine. Unlike o-vanillin and N-benzylidene-l-lysine, -amino--caprolactam was found to be rather ineffective in modulating polymer architecture. [ABSTRACT FROM AUTHOR]