Form-function relationships underlie rapid dietary changes in a lizard.

Macroevolutionary changes such as variation in habitat use or diet are often associated with convergent, adaptive changes in morphology. However, it is still unclear how small-scale morphological variation at the population level can drive shifts in ecology such as observed at a macroevolutionary scale. Here, we address this question by investigating how variation in cranial form and feeding mechanics relate to rapid changes in diet in an insular lizard (Podarcis siculus) after experimental introduction into a new environment. We first quantified differences in the skull shape and jaw muscle architecture between the source and introduced population using three-dimensional geometric morphometrics and dissections. Next, we tested the impact of the observed variation in morphology on the mechanical performance of the masticatory system using computer-based biomechanical simulation techniques. Our results show that small differences in shape, combined with variation in muscle architecture, can result in significant differences in performance allowing access to novel trophic resources. The confrontation of these data with the already described macroevolutionary relationships between cranial form and function in these insular lizards provides insights into how selection can, over relatively short time scales, drive major changes in ecology through its impact on mechanical performance.

Fabrication of hybrid Fabry-Pérot microcavity using two-photon lithography for single-photon sources.

For an efficient single-photon source a high-count rate into a well-defined spectral and spatial mode is desirable. Here we have developed a hybrid planar Fabry-Pérot microcavity by using a two-photon polymerization process (2PP) where coupling between single-photon sources (diamond colour centres) and resonance modes is observed. The first step consists of using the 2PP process to build a polymer table structure around previously characterized nitrogen-vacancy (NV) centres on top of a distributed Bragg reflector (DBR) with a high reflectivity at the NV zero-phonon line (ZPL). Afterwards, the polymer structure is covered with a silver layer to create a weak (low Q) cavity where resonance fluorescence measurements from the NVs are shown to be in good agreement with analytical and Finite Difference Time Domain (FDTD) results.

Cross-border patterns in DNA matches between the Netherlands and Belgium.

In this article we present the results of a study to explore if cross-border DNA matches between the Netherlands and Belgium are relatively more likely to occur in areas near the Dutch-Belgian border than in areas at some distance from this border. For this study we used the results of the transnational DNA profile exchange and comparison between the Belgian and Dutch DNA databases, which first took place in 2014. It appears that the Dutch regions adjacent to Belgium, i.e., Zeeland-West-Brabant, Oost-Brabant and Limburg, have relatively more DNA matches with Belgium than the other Dutch regions. In other words, a DNA profile obtained from a crime scene close to the Dutch border with Belgium is more likely to match with the profile of a person whose DNA profile is stored in the Belgian database than a DNA profile that originates from a crime scene further afield. Our data suggest that crimes committed by repeat offenders show a spatial pattern despite the presence of a national border, with crime scenes clustering in relatively close proximity to each other. The results of this study provide a better understanding of geographical patterns of cross-border criminal mobility.

Rangeland Rummy - a board game to support adaptive management of rangeland-based livestock systems.

Rangeland-based livestock systems have to deal with the significant instability and uncertainty of the agricultural context (policy changes, volatility of input prices, etc.), and especially of the climatic context. Thus, they are particularly concerned by adaptive management strategies. To support the development of such strategies, we developed a board game including a computer model called "Rangeland Rummy". It is to be used by groups of farmers and agricultural consultants in the context of short workshops (about 3 h). Rangeland Rummy builds upon five types of material object: (i) a game board; (ii) a calendar stick indicating the starting date of the game board; (iii) sticks marked with the feed resources available for combinations of vegetation types and their management practices; (iv) cards to define animal groups and their feeding requirements throughout the year; (v) cards related to types of feed that can be attributed to animal groups throughout the year. Using these material objects, farmers collectively design a rangeland-based livestock system. This system is immediately evaluated using a computer model, i.e. a spreadsheet providing graphs and indicators providing information on, among other things, the extent to which quantitative and qualitative animal feeding requirements are covered across the year. Playing the game thus consists in collectively and iteratively designing and evaluating rangeland-based livestock systems, while confronting the players with new contextual challenges (e.g. interannual variability of weather, volatility of input prices) or new farmers' objectives (e.g. being self-sufficient for animal feeding). An example of application of Rangeland Rummy with 3 farmers in southern France is reported. Applications show that it tends to develop farmers' adaptive capacity by stimulating their discussions and the exchange of locally-relevant knowledge on management strategies and practices in rangeland-based livestock systems.

Characterisation of pregnancy losses after embryo transfer by measuring plasma progesterone and bovine pregnancy-associated glycoprotein-1 concentrations.

The aim of this analysis was to determine whether pregnancy loss (PL) after embryo transfer (ET) in cattle was related to maternal progesterone (P4) concentrations during and shortly after ET, and maternal bovine pregnancy-associated glycoprotein-1 (bPAG-1) concentrations in plasma at days 25-35 of gestation. Embryos (n=260) were produced either in vivo after superovulation (n=115), or in vitro from oocytes (obtained with ovum pick-up) in co-culture (n=44) or cultured in a synthetic medium (n=101). Overall, PL was 56.9% (148) and no significant differences occurred in calving rate among the three embryo production groups. There was no difference in P4 concentrations on days 7-14 of gestation in the three groups, nor between ongoing and interrupted pregnancies. Between days 25 and 35 of pregnancy, bPAG-1 concentrations were unaffected by embryo production, but in cattle that had PL between days 26 and 120, four bPAG-1 profiles could be detected. Between days 25 and 32, bPAG-1 concentrations were influenced by PL, and concentrations were significantly lower in animals in which PL occurred between days 26 and 120 than in those animals that aborted later or calved at term. Early P4 concentrations suggested that maternal luteal factors were not responsible for PL which appeared to be caused by impaired conceptus development (regardless of embryo type) as reflected by low maternal bPAG-1 concentrations prior to embryonic death.

The effect of two different routes of administration of oxytocin on peripheral plasma prostaglandin F(2α) metabolite levels in early post-partum dairy cows.

Various parenteral treatment forms of oxytocin, as often used under praxis circumstances, may act differently on contractility of the uterus during the first days of the puerperium. Various patterns of such induced uterotonic responses may lead to alterations in the emptying characteristics of the uterine lumen, thus influencing, as a late consequence, the process of involution. Therefore, this study was designed to test whether two different parenteral administration forms of oxytocin induce changes in peripheral plasma concentrations of 15-ketodihydro-prostaglandin F(2α) (PGF(2α) metabolite) in early post-partum cows. Between 13 and 15 h after uncomplicated calving, healthy dairy cows without retained foetal membranes were treated with 50 IU oxytocin, either intramuscularly (OT-IM group; n = 15) or intravenously (OT-IV group; n = 16). Saline solution was administered intramuscularly as controls (CON group; n = 15). Jugular blood samples were taken at 10-min intervals from 1 h before to 2 h after treatment. Plasma PGF(2α) metabolite levels were measured by radioimmunoassay. No significant differences in peripheral plasma PGF(2α) metabolite concentrations occurred in the OT-IM and CON groups, but mean values significantly increased in the OT-IV group, peaking at 20 min after treatment and reaching pre-treatment baseline values again at 120 min. Although the source of prostaglandins was not investigated in this study, our results suggest that exogenous oxytocin may enhance secretion of prostaglandins by the uterus during the first day after normal calving. These prostaglandins might contribute, by an endocrine or paracrine route, to the stimulation of myometrial contractility when exogenous oxytocin is given during this early post-partum stage.

Fetal movements during late gestation in the pig: a longitudinal ultrasonographic study.

Repeated ultrasonographic observation of fetal movements was used to distinguish movement patterns and to investigate the rate of occurrence and temporal organisation of these patterns (rest-activity cycles) during the last three weeks of gestation in the pig. By means of transabdominal ultrasonography with a 3.5MHz linear array transducer, motility in ten different fetuses (one per sow) was studied. Six (median; range 4-6) 1h recordings were made per fetus at 3-5 day intervals. Fifty-five 1h recordings were available for analysis. The occurrence of fetal general movements (GM), isolated head (HM), forelimb movements (LM), and rotations (ROT) was analysed from video tapes. For each movement pattern, the trend in occurrence over time was assessed by multilevel analysis. The temporal association between different movement patterns was studied by calculation of the kappa value. ROT occurred very infrequently and showed no particular trend over time. GM, HM, and LM showed a significant decreasing trend towards parturition (P<0.01). Total fetal activity (i.e., the sum of the four movement incidences) declined from an average of 25% of recording time to 9% over the last three weeks of pregnancy. Periods of fetal quiescence gradually increased with progressing gestation (P<0.05). There was no evidence of concordant association between the periods of rest and activity of GM, HM, and LM or of improved temporal linkage between these movement patterns with time. Fetal bodily activity decreases towards parturition mainly due to prolonged periods of rest. Fetal movement patterns show rest-activity cycles, but each pattern appears to cycle independently from the other throughout late gestation. The present results of spontaneous fetal movements in the pig provide reference data for future studies of fetal activity under different zoo technical conditions or pharmacological interventions.

Cervical ripening and parturition in cows are driven by a cascade of pro-inflammatory cytokines.

The final stages of cervical ripening and parturition resemble an inflammatory process. Although the role of cytokines in both spontaneous and experimentally induced parturitions has been described in several small laboratory animals and humans, the involvement of pro-inflammatory and regulatory cytokines in physiologic parturition in cows has not been determined. In this study, the cytokine expression profiles were assessed in bovine cervical tissue at several stages of pregnancy and at parturition. Serial biopsy samples of the cervix were obtained from 10 cows on day 185 and day 275 of pregnancy (which was on average 5.4 days before parturition) and at parturition. Messenger RNA expression levels of interleukin (IL)-1beta, IL-6, IL-8, IL-10 and tumour necrosis factor (TNF)alpha were determined using real-time polymerase chain reaction and the number of neutrophils and eosinophils was estimated by Luna and Sirius Red staining. At parturition, IL-8 expression had increased 430-fold (p < 0.001) when compared with that of the day 185 of pregnancy, large numbers of neutrophils had invaded the cervix while eosinophils remained scarce, IL-1beta had increased eightfold (p < 0.05) and IL-6 had not changed significantly. Additionally, IL-10 was increased by 10-fold (p < 0.001) and TNFalpha decreased by 57% (p < 0.05) when compared with that of the day 185 of pregnancy. The large increase in expression of IL-8, enabling the influx of neutrophils, is indicative of its important role in the final stage of cervical ripening and at parturition. As previous studies have shown that neutrophils excrete matrix metalloproteinases (MMP), this might contribute to softening of the cervix. In contrast, the only slightly increased levels of IL-1, steady concentrations of IL-6 and decreased TNFalpha, the potential consequences of increased IL-10 expression, indicate that final cervical of cows in ripening at term parturition is an inflammatory process influenced by regulatory cytokines.

Improving adaptation to weaning: effect of intermittent suckling regimens on piglet feed intake, growth, and gut characteristics.

Daily separation of sows and piglets during lactation, intermittent suckling (IS), improves feed intake and postweaning adaptation in piglets. The aim of the current study was to determine how, in piglets that have been subjected to IS, age at weaning and the duration of the preceding IS period contribute to postweaning adaptation through effects on feed intake, growth, and gut characteristics. All piglets had ad libitum access to creep feed from d 7. Litters were subjected to conventional weaning (CW) or to 1 of 3 IS regimens. In CW, litters (n = 29) had continuous access to the sow until weaning (d 26, d 0 = farrowing). During IS, litters had access to the sow between 1600 and 0600 h. Litters in the IS treatments were subjected to IS 1) from d 19 onward and weaned at d 26 (IS19-7D, n = 33), 2) from d 19 onward and weaned at d 33 (IS19-14D, n = 28), or 3) from d 26 onward and weaned at d 33 (IS26-7D, n = 33). The IS19-7D regimen resulted in a relative growth check within the first 2 d after weaning similar to CW litters (72 +/- 13 and 90 +/- 7%, respectively), but in a greater piglet growth (P = 0.014) and feed intake (P = 0.001) between d 2 and 7 postweaning. Moreover, IS19-7D was not associated with a (further) reduction in villus height as observed at d 2 postweaning in CW litters. In IS piglets weaned after an extended lactation (d 33), a markedly smaller weaning-associated relative growth check was observed shortly postweaning (11 +/- 18 and 32 +/- 19% for IS19-14D and IS26-7D litters, respectively). In these litters, feed intake and growth within the first 2 d after weaning were slightly greater when piglets were subjected to IS for 2 wk (IS19-14D) rather than for 1 wk (IS26-7D; P = 0.032 and P = 0.037 for feed intake and growth, respectively). Irrespective of duration of IS, weaning at d 33 with IS was not associated with a reduction in villus height. Irrespective of treatment, plasma citrulline concentrations were reduced at d 2 and 8 postweaning compared with the values at weaning (P < or = 0.01). No correlation was observed between postweaning plasma citrulline concentrations and postweaning small intestinal villus height. This study indicates that 1 wk of IS before weaning at d 26 of lactation improves feed intake and growth between d 2 and 7 postweaning and does not result in a reduction of villus height as observed in CW piglets, although it did not prevent a profound growth check shortly after weaning. However, combining 1 wk of IS with an extended lactation improved postweaning adaptation markedly in terms of growth, feed intake, and gut characteristics. Increasing the duration of IS from 1 to 2 wk slightly improved growth and feed intake shortly after weaning, but the contribution to postweaning adaptation seemed to be relatively small compared with extending lactation.

Ontogeny of fetal movements in the guinea pig.

Assessment of fetal motility is an approach to evaluate the development and function of the nervous system before birth. Reference values for the time of first occurrence and the incidence of normal fetal movements are indispensable for studies in which prenatal motor activity is applied as a model to study the central and peripheral nervous systems. Studies on fetal motility have been performed in a few species, particularly in the human. The aim of the present study is to describe the ontogeny of fetal motility in the guinea pig, a precocious polytocous species. After a pilot study to establish procedures for repeated ultasonographic scanning of guinea pigs, 10 domesticated animals were scanned (5.0 or 7.5 MHz convex transducer) at 2-4 day intervals between day 24 and 63 of gestation (term age 68 days). Per animal two selected fetuses were each scanned for 15 min. Images were stored on videotape and analyzed off-line for the first onset, presence and quality of fetal movement patterns, and quantity of sideway bendings, general movements, breathing movements and periods of fetal rest. Twenty-five different movement patterns could be characterized, 6 emerging at the onset of motor activity were performed only temporarily. The very first fetal movement was observed on day 24 gestational age, and subsequently most other movements developed during a period of only 5 days. Interfetal difference in onset of the frequently occurring sideway bendings, general movements, and front and hind limb movements was only 2 days. Sideway bendings and general movements co-existed during days 29 to 43. There were developmental trends in the course of pregnancy. Sideway bendings increased rapidly between 24 and 30 days and declined hereafter. General movements and fetal breathing increased during midpregnancy and declined towards parturition. Conversely, fetal rest was observed for approximately 60% of time at midgestation and a marked increase was found towards parturition. There were no significant differences in developmental trend of the various movement patterns between individual fetuses. Fetal motility in the guinea pig followed a specific temporal pattern, like in the human, but at a different time scale. The present quantitative data will enable functional investigations into the role of the neuromuscular system. They may also facilitate studies on the effect of environmental influences, such as stress, drugs, toxic substances, and food conditions, on fetal neurobehavioural development in this species.

Smooth muscle cells of the bovine cervical stroma may have a secretory, rather than a contractile function during parturition.

The bovine cervix contains a large amount of smooth muscle cells distributed over an outer muscular layer and within a stromal layer. The stromal layer exhibits no electromyographic (EMG) activity at parturition. This leads to the question whether the stromal smooth muscle cells of the bovine cervix are prepared to contract with parturition, or whether they have another function. To this end, cervical biopsies were repeatedly taken from 10 pregnant cows at day-185 and -275 of gestation, at spontaneous, uncomplicated calving and at 30 days after calving. The smooth muscle bundles of the stroma were immunohistochemically analysed (n = 5) with regard to their integrity and cellular density, and the degree of staining for connexin-43, smooth muscle actin alpha (SMA), desmin and vimentin. Additionally, the mRNA expression for connexin-43, SMA, desmin and vimentin was determined with RT-PCR (n = 5). The smooth muscle tissue was arranged in bundles, also at parturition. However, the cellular density of these bundles and the SMA mRNA expression were decreased at parturition. Additionally, the SMA staining and connexin-43 expression and staining remained constant during pregnancy and at parturition. This might indicate that stromal smooth muscle cells are not prepared to contract with parturition, in contrast to the myometrial smooth muscle cells. The smooth muscle cells, stained for SMA, also expressed vimentin, and the proportion of co-expression was increased at day-275 of pregnancy. This suggests that the stromal smooth muscle cells predominantly have a secretory function in cows.

Follicle dynamics and its relation with plasma concentrations of progesterone, luteinizing hormone and estradiol during the egg-laying cycle in ostriches.

The aims of this study were (i) to describe the changes in the volume of large ovarian follicles (diameter >3 cm) during the 48 h egg laying cycle in farmed ostriches, and (ii) to quantify factors affecting the volume of the largest measured follicle and the plasma concentrations of progesterone (P(4)) and estradiol-17beta (E(2)beta). In eight egg-producing birds, which all ovulated during the study period, transcutaneous ultrasound scanning and blood sampling was performed at 3 h intervals. The average volume of the total number of visualized large follicles (V(total)), the largest measured follicle (V(F1)), the second largest follicle (V(F2)) and of all follicles smaller than F2 (V(F3-Fn)) were each higher before than after oviposition. V(total), V(F2) and V(F3-Fn) nearly doubled in the 24-h period before oviposition, while V(F1) remained at an equal, rather high level until oviposition. Immediately after oviposition V(total), as well as the volume of the other follicle categories, decreased within 6 h, i.e. around the moment of ovulation. By performing statistical analysis on the basis of linear mixed-effects modelling, we quantified that: (i) V(F1) was 13.2% higher before than after oviposition and increased with 6.5% when LH increased with 1 ng/ml; (ii) P(4) levels were 93.2% higher before than after oviposition and increased with 43.1% for every 3 h closer to oviposition; when LH and E(2)beta levels and V(F1) increased with 1 ng/ml, 10 pg/ml and 10 ml, respectively, P(4) increased with 116.6%, 50% and 6.1%; and (iii) E(2)beta levels were 35.6% higher before than after oviposition, increased with 2.7% for every 3 h closer to oviposition and increased with 14.6% when LH increased with 1 ng/ml. It is concluded that during the egg-laying cycle in ostriches: (i) follicular mass, as estimated by the volume of visualized follicles larger than 3 cm, increases before and decreases after ovulation, and (ii) follicular dynamics and its accompanying endocrine plasma hormone profiles during the egg-laying cycle in ostriches follow a pattern similar to that in chickens.

Intermittent suckling enables estrus and pregnancy during lactation in sows: effects of stage of lactation and lactation during early pregnancy.

Previously we demonstrated that pre-ovulatory LH and post-ovulatory progesterone (P4) concentrations in plasma were low and embryo development was retarded when sows were induced to ovulate during lactation by submitting them to intermittent suckling (IS). The present study investigated whether this was due to: (1) stage of lactation when IS was initiated, and (2) continuation of IS post-ovulation. Multiparous Topigs40 sows were studied under three conditions: conventional weaning at Day 21 of lactation (C21; n=30), intermittent suckling from Day 14 of lactation (IS14; n=32), and intermittent suckling from Day 21 of lactation (IS21; n=33). Sows were separated from piglets for 12h daily during IS. IS sows were either weaned at ovulation or 20d following ovulation. One-third (21/63) of the IS21 and C21 sows had already ovulated or had large pre-ovulatory follicles at Day 21 and were excluded from further study. Initiation of IS at Day 14 instead of Day 21 of lactation tended to reduce P4 at 7d post-ovulation (P=0.07), did not affect pregnancy rate, and tended to reduce embryo survival (P=0.06). Continuation of IS during pregnancy resulted in lower P4 at 7 and 12d post-ovulation, tended to reduce embryo weight and pregnancy rate (P<0.10), whereas embryo survival was not affected. This study presents data for a population of sows in which follicle growth and ovulation are easily triggered under suckling conditions. Further, when these sows are bred during lactation, initiation of IS at 21 rather than 14d of lactation with weaning at ovulation yields the most desirable reproductive performance.

Parturition in domestic animals: targets for future research.

Contents Compared with other parts of the reproductive cycle, the parturition process of domestic animals has received relatively little attention from researchers during the last two decades. Yet, interventions during parturition, either by the owner or the veterinarian, are frequently judged necessary and perinatal losses in most of the domestic species are (still) rather high. The present paper focuses on the birth process in three domestic species, the dog, pig and cow, mainly because most of the experimental and research work of the authors themselves was dealing with these three species. Against the background of specific clinical problems, breeding circumstances and economic performance, selected topics and questions are addressed to identify areas for future research. These are, among others, related to the mechanisms that trigger the birth process (are the foetuses involved in the dog and sow?), the role of hormones and cytokines during ripening of the cervix (activation and/or de-activation of specific matrix metallo-proteinases and their local inhibitors), the functional significance of fetal body movements to prepare the foetus for expulsion, and the exact time course of events involved in the transportation of an individual foetus from its intrauterine location, via the pelvic canal, to the outside world. Research on some of these topics, such as the ripening of the cervix in cows, might also contribute to resolve clinical problems in human obstetrics.

Placental transfer and pharmacokinetics of allopurinol in late pregnant sows and their fetuses.

At present no standard pharmacological intervention strategy is available to reduce these adverse effects of birth asphyxia. In the present study we aimed to evaluate placental transfer of allopurinol, an inhibitor of XOR. For this purpose, fetal catheterization of the jugular vein was conducted in five late pregnant sows (one fetus per sow). At 24-48 h after surgery, sows received allopurinol (15 mg/kg body weight; i.v.) and pharmacokinetics of allopurinol and its active metabolite oxypurinol were measured in both late pregnant sows and fetuses. Maternal and fetal blood samples were collected during and after allopurinol administration. Maternal C(max) values averaged 41.90 microg/mL (allopurinol) and 3.68 microg/mL (oxypurinol). Allopurinol crossed the placental barrier as shown by the average fetal C(max) values of 5.05 microg/mL at 1.47 h after allopurinol administration to the sow. In only one fetus low plasma oxypurinol concentrations were found. Incubations of subcellular hepatic fractions of sows and 24-h-old piglets confirmed that allopurinol could be metabolized into oxypurinol. In conclusion, we demonstrated that allopurinol can cross the placental barrier, a prerequisite for further studies evaluating the use of allopurinol as a neuroprotective agent to reduce the adverse effects following birth asphyxia in neonatal piglets.

Citrulline and intestinal fatty acid-binding protein: longitudinal markers of postweaning small intestinal function in pigs?

The objective of the current study was to investigate whether plasma citrulline or intestinal fatty acid-binding protein (I-FABP) concentrations might be used as longitudinal markers for small intestinal function in piglets after weaning. Plasma citrulline and I-FABP concentrations were measured longitudinally in weaned and unweaned piglets, and related to intestinal absorption values (i.e., plasma mannitol and 3-xylose concentrations in a sugar absorption test). Within each litter (n = 10), 2 piglets with a close-to-litter-average BW were selected. At 20.8 +/- 0.4 d of age, the selected piglets per litter were either weaned conventionally (CW) or remained with the sow (UNW). One day before, and 0.5, 2, 4, and 7 d after weaning of the CW piglets, the selected piglets of both groups were subjected to a sugar absorption test. After a 2-h fast, piglets were administered an oral dose of 2 mL/kg of sugar solution, containing 50 mg/kg of mannitol and 100 mg/kg of 3-xylose. One hour after administration, a blood sample was collected from a jugular vein for determination of plasma I-FABP, citrulline, mannitol, and 3-xylose concentrations. Plasma I-FABP concentration showed great variation within treatments, and no difference was observed in plasma I-FABP concentrations between the CW and UNW treatments (P = 0.63). The absorption of 3-xylose was not different between treatments (P = 0.83). Mannitol absorption, however, was less in the weaned CW piglets compared with the UNW piglets (P = 0.003), with the nadir on d 4 postweaning. Weaning also reduced plasma citrulline concentrations in the CW treatment compared with the UNW treatment (P < 0.001). On d 4 and 7 postweaning, plasma citrulline concentrations of CW piglets were less (P < 0.001 and P = 0.0013) than preweaning values. Furthermore, in the CW treatment, plasma citrulline concentrations correlated with plasma mannitol concentrations at d 4 postweaning (r = 0.89, P = 0.008) and overall (r = 0.76, P = 0.001). Based on these results, plasma citrulline concentration seems to be a possible marker for monitoring intestinal function in pigs after weaning.

The relation between the birth process and the condition of the newborn piglet and calf.

This presentation will focus on the assessment of the condition of the piglet and calf during and shortly after birth and will review some of the physiological and clinical factors that may have played a role during their delivery and influenced their viability at birth.

Umbilical cord clamping in term piglets: a useful model to study perinatal asphyxia?

Perinatal asphyxia results in tissue and cellular changes during the reperfusion period and clinical signs like perinatal mortality and decreased vitality at birth in newborn piglets. This study aimed to develop and validate a model of birth asphyxia, mimicking the evolvement of birth asphyxia in natural farrowings by conducting umbilical cord clamping (UCC) in term piglets during caesarean sections under general anaesthesia. In total 23 piglets were subjected to 5-8min of UCC and 24 piglets served as controls. Acid-base balance values and heart rates measured before UCC remained fairly constant throughout the surgical procedure, indicating nearly identical starting conditions of piglets within and between litters. UCC resulted in a significant, mild, mixed respiratory-metabolic acidosis (pH 7.22, pCO(2) 9.8kPa, BE(ecf) 2mmol/L, lactate 6.5mmol/L; controls: pH 7.31, pCO(2) 8.5kPa, BE(ecf) 5mmol/L, lactate 4mmol/L) at 10min after birth (defined as simultaneous cutting of the umbilical cord and removal of a plastic bag that had been placed over the head to avoid air intake). Heart rates were significantly decreased during UCC (range: 83-107beats/min versus 128-134beats/min in controls). Rectal temperatures and changes in body weight until 72h of life were not affected by UCC. Interestingly, four control and seven clamped piglets did not survive as no independent respiration could be attained. Birth weights and duration of UCC of these piglets did not differ significantly from those in surviving control and clamped piglets. In conclusion the mixed respiratory-metabolic acidosis arising in the surviving clamped piglets is not as severe as can be expected in highly asphyxiated, vaginally delivered newborn piglets. Repeatability of the model is compromised by considerable variation in the individual response to UCC.

Prenatal stress in pigs: experimental approaches and field observations.

Prenatal stress can affect the offspring's behaviour, physiology, and immune parameters. This paper summarises and discusses experimental and field studies on prenatal maternal stress in pigs. Often, elevated maternal corticosteroid concentrations during gestation are used to model prenatal stress. We used prolonged oral administration of cortisol (hydrocortisone acetate, HCA) to pregnant sows, which resulted in elevated maternal plasma and salivary cortisol concentrations. This treatment induced elevated fetal basal and adrenocorticotropic hormone (ACTH)-induced plasma cortisol concentrations, as demonstrated by a pilot study. Postnatally, it reduced birth weight of the piglets, and resulted in more live born piglets and higher preweaning mortality. In addition, it reduced the female offspring's salivary cortisol response to ACTH, and it enhanced the piglets' novelty-induced locomotion and vocalisations, and the piglets were more aggressive in a social test. Some of these effects depended on the period of gestation during which maternal cortisol concentrations were elevated, and on the sex of the offspring. These results demonstrate that piglet physiology and behaviour can indeed be affected when the mother has elevated cortisol concentrations during gestation. Regular mixing of pregnant sows with unfamiliar sows during the last third of gestation did not affect maternal salivary cortisol concentrations. Also, it did not affect the piglets' performance, behaviour, adrenocortical response to ACTH, or wound healing. Regular mixing of pregnant sows during the last third of gestation did not affect the piglets' characteristics as studied in these experiments. However, performance and behaviour of piglets were highly influenced by the social rank of their mother during gestation. Our studies have demonstrated that piglets can be affected by elevated maternal cortisol concentrations during fetal development and by social rank of the pregnant sow during gestation.