Location and Setting of the Mars InSight Lander, Instruments, and Landing Site.

Knowing precisely where a spacecraft lands on Mars is important for understanding the regional and local context, setting, and the offset between the inertial and cartographic frames. For the InSight spacecraft, the payload of geophysical and environmental sensors also particularly benefits from knowing exactly where the instruments are located. A ~30 cm/pixel image acquired from orbit after landing clearly resolves the lander and the large circular solar panels. This image was carefully georeferenced to a hierarchically generated and coregistered set of decreasing resolution orthoimages and digital elevation models to the established positive east, planetocentric coordinate system. The lander is located at 4.502384°N, 135.623447°E at an elevation of -2,613.426 m with respect to the geoid in Elysium Planitia. Instrument locations (and the magnetometer orientation) are derived by transforming from Instrument Deployment Arm, spacecraft mechanical, and site frames into the cartographic frame. A viewshed created from 1.5 m above the lander and the high-resolution orbital digital elevation model shows the lander is on a shallow regional slope down to the east that reveals crater rims on the east horizon ~400 m and 2.4 km away. A slope up to the north limits the horizon to about 50 m away where three rocks and an eolian bedform are visible on the rim of a degraded crater rim. Azimuths to rocks and craters identified in both surface panoramas and high-resolution orbital images reveal that north in the site frame and the cartographic frame are the same (within 1°).

A Nordic survey of management practices and owners' attitudes towards keeping horses in groups.

Keeping horses in groups is widely recommended but limited information is available about how this is implemented in practice. The aim of this survey was to describe how horses are kept in the Nordic countries in relation to sex, age, breed, and equestrian discipline and to assess owners' attitudes toward keeping horses in groups. Horse owners in Denmark, Finland, Norway, and Sweden were approached using a web-based questionnaire, which was translated into 4 languages and distributed online via equestrian forums, organizations, and social media. The number of respondents was 3,229, taking care of 17,248 horses. Only 8% of horses were never kept in groups, 47% were permanently grouped for 24 h/d, and 45% were stabled singly but grouped during turnout. Yearlings were most often permanently kept in groups (75%), mares and geldings more commonly during parts of the day (50 and 51%, respectively), and stallions were often kept alone (38%). Icelandic horses were more likely to be permanently kept in groups (36%) than warmbloods (16%) and ponies (15%). Twice as many competition horses (51%) were never grouped compared with horses used for breeding (20%) or leisure purposes (15%). The majority of respondents (86%) strongly agreed that group housing benefits horse welfare and that it is important for horses to have the company of conspecifics (92%). Nevertheless, not all horses were kept in groups, showing that attitudes toward group housing may not necessarily reflect current management. The risk of injury was a concern of many respondents (45%), as was introducing unfamiliar horses into already established groups (40%) and challenges in relation to feeding in groups (44%). Safety of people (23%) and difficulties handling group-kept horses (19%) were regarded as less problematic. Results suggest that the majority of horses have the possibility to freely interact with other horses, either as fulltime members of a group during 24 h/d or during turnout. Future research should address the extent to which being a part-time member of a group affects horse welfare. For permanent group housing to become more widespread, such as it is the case for most farm animals, future research could focus on solving some of the reoccurring problems perceived with keeping horses in groups. The dissemination of evidence-based information on all aspects around keeping horses in groups can ultimately stimulate further positive changes in the management of group-kept horses.

Leg health and performance of broiler chickens reared in different light environments.

1. The effects of light source and intensity on leg health and performance of female ROSS 308 broiler chickens were investigated in a 2 x 2 experimental design (8 groups of 275 chicks) of two light sources (Osram biolux and Osram warm-white) and two light intensities (5 and 100 clux, adjusted to fowl-perceived illuminance). 2. At 41 d of age, body weight, gait-score, footpad dermatitis and hock-burn were measured on 50 birds from each light environment. In addition, weekly feed intake and body weight were determined on a group basis and mortality was recorded continuously. 3. The light environment did not affect the severity of the gait-score or hock-burns. The risk of moderate to severe lameness and hock-burns increased with body weight. Birds weighing more than 2400 g had an increased probability of moderate footpad lesions in biolux light. 4. Weight and gait-score, as well as gait-score and hock-burn were positively correlated. Podo-dermatitis was weakly correlated with hock-burn, which contradicts earlier findings. The light environment did not affect feed intake, body weight or mortality. 5. The light sources and intensities employed in this study did not adversely affect production or leg health of broiler chickens reared semi-commercially.

A laser-based method to measure thermal nociception in dairy cows: short-term repeatability and effects of power output and skin condition.

To validate a laser-based method to measure thermal nociception in dairy cows (e.g., for the use in studies on stress-induced analgesia), we performed three experiments to observe the behavioral responses to a computer-controlled CO2 laser beam applied to the skin on the caudal aspect of the metatarsus. In Exp. 1, effects of power output (0, 1.3, 1.8, 2.2, 2.4 and 2.6 W) on nociceptive responses were examined using 18 dairy cows kept and tested in tie stalls. Increasing the power output affected the latencies to respond (decreasing latencies, P < or = 0.01), types of response (less nonresponding and more kicking, P < 0.0001), and behavior during (increasing frequency of tail flicking, P = 0.003) and between single laser exposures (increasing frequency of kicking, P = 0.02). Therefore, behavioral responses to a laser stimulus seem to be a valid measure of nociception in dairy cows. Repeatability within 15 min was investigated in Exp. 2 using n = 36 dairy cows kept and tested in tie stalls and a power output of 1.8 W. The variables' latency to move the exposed leg and frequency of tail flicking during laser exposure showed the highest level of repeatability (0.50 and 0.38, respectively). However, retesting at t = 15 min led to increased responses in terms of shorter latencies to respond (P < 0.05), increased kicking (P = 0.05), and tail flicking (P = 0.02), which probably can be explained by sensitization. Effects of power output (1.0 vs. 1.8 W) and skin condition (naked vs. intact) were examined in Exp. 3 on 11 group-housed dairy cows, tested just outside their home pen. Increasing the power output and shaving off hair led to increased responses as seen by shorter latencies to respond (P < 0.0001), less nonresponding (P < 0.0001), and increased kicking (P = 0.0003), as well as reduced intra- and interindividual variability (P < or = 0.04). In conclusion, the results of these experiments suggest that behavioral responses to laser stimulation are a valid and reliable measure of nociception in dairy cows, especially when applied on naked skin, both in the home environment and just outside a group pen. The fact that repeated testing in itself at t = 15 min led to increased responses means that the test will be a conservative measure of stress-induced analgesia.

Effects of interrupted social contact on the social behaviour of calves and piglets.

The use of traditional operant conditioning techniques to assess the behavioural needs of farm animals has been criticised because presenting short rewards repeatedly may interrupt bouts of behaviour and thereby devalue the reward. The two reported experiments (one including 12 calves and one including 12 piglets) aimed to investigate if interruption of social contact affects social behaviour. In both experiments, animals were housed in pairs (one test animal and one companion animal) in large pens with solid sides. The experiment included three periods: a pre-test period, a test period and a post-test period. Animals were separated for 24 h and then reunited for 24 h in each period. In the test period, the first 42 min of contact after reunification comprised 12 successive 3.5 min long periods separated by gaps, whereas in the pre- and post-test periods, the contact was continuous. Calves sniffed and licked each other more when social contact was interrupted (P<0.01), but no effects of interrupting social contact were found for social or locomotor play. In piglets, the test animals performed more flank pushing of the companion (P<0.01), and avoided the companion more (P<0.05), when social contact was interrupted, while no effects of interruption were found for parallel pressing, bites and head knocks, sniffing or locomotor play. The results suggest that if social contact is interrupted in an operant conditioning set up, some elements of aggressive behaviour may be stimulated in piglets.

Alternative microbial testing: a novel DNA-based detection system for specified microorganisms in pharmaceutical preparations.

Fluorescence-coupled PCR technology was employed to quantify DNA segments specific for Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacteriaceae. The PCR procedure is put forward as an alternative method for detecting microbial contaminations in pharmaceutical preparations and is compared to the tests for specified microorganisms described in European Pharmacopoeia (EP) 2, 2.6.13 and the USP, chapter 61. Data presented here describe the validation of this analytical method when used for proof of absence of specified microorganisms. The detection systems were specific for the microorganisms analyzed, and led to linear results over a wide range (more than 6-7 log intervals). The correlation coefficients lay above 0.99. The precision of replicate determinations within a single test was observed to be high, the relative standard deviation being between 0.39% and 1.53%. The precision between different tests was also high, with a relative standard deviation between 0.76% and 1.91%. The sensitivity without pre-enrichment amounted to 1-10 CFU. Since determination of the specified bacteria was performed following pre-enrichment, the limit of detection amounted to 1 CFU. Equivalent results were obtained in a study on nine batches of a milky hydrophilic cream (SH-No. M 440 A) with the conventional test for microbial contamination and the PCR procedure. The data presented here strongly indicate that the use of fluorescence-coupled PCR techniques can prove the absence of specified bacteria faster and more efficiently than conventional methods.

The effect of irregular feeding times on the behaviour and growth of dairy calves.

The objective of this study was to examine the effects of predictable vs. unpredictable management routines on the behaviour, production and health of dairy calves. Three different feeding schedules for milk-fed dairy calves were compared. All calves received milk twice a day, and had free access to concentrate, hay and water. Three groups of 12 calves (divided on two trials) were exposed to one of the following treatments from the age of 5 days to 9 weeks: group C (control) received milk at the same time every day, at 0700 and 1400. Group OD (occasional deviation) received the milk at the same time every day except on treatment days, one in week 5 and one in week 8, where they were fed 3 h later. Group IR (irregular schedule) received milk at irregular times throughout the experimental period. The first daily feeding took place between 0600 and 1300 and the second one between 1300 and 2100. When the calves were 5 and 8 weeks old, the behaviour of eight calves from each group was videorecorded for two days (48 h). The following behaviour was recorded: frequency and duration of lying bouts and frequency of comfort behaviour (defined as licking or scratching own body), eating, drinking, other oral behaviour and extending the head through the feeding barrier (HTB). The milk and concentrate consumption of the calves was measured and the calves were weighed weekly. Diseases were recorded.The results showed that at the age of 5 weeks, the calves in group IR differed from the control group C by performing more eating behaviour both on the control day (27.5 vs. 15.5; p<0.05) and the treatment day (28.8 vs. 18.3; p<0.05). At the age of 8 weeks, no differences were found in the behaviour between groups IR and C. When the OD calves were 5 weeks old, they responded to the delayed feeding by increasing drinking behaviour (14.5 vs. 9.0; p<0.05). When they were 8 weeks old, they showed increased frequency of comfort (195 vs. 122; p<.05), eating (37.5 vs. 27.9; p<0.05) and HTB behaviour (19.8 vs. 7.4; p<0.001) on the treatment day compared to the control day. The IR group did not respond to the same treatment except for a slight increase in drinking behaviour (9.6 vs. 6.5; p<0.05) at the age of 8 weeks. No differences were observed in the frequency or length of lying bouts, nor health or production parameters between the three groups.It is concluded that a predictable feeding schedule may not be very important for milk-fed dairy calves. However, when the calves are customised to predictable feeding times, occasional deviations from that schedule may cause frustration when their expectations are not fulfilled.

The effects of branches on prepartum nest building in gilts with access to straw.

Sows farrowing in a semi-natural environment terminate nest building 1-7 h prior to parturition after having built a nest for which a variety of materials are used. No nest-building behaviour occurs during parturition and the sows remain lying in the nest throughout most of the farrowing. In contrast, many intensively housed sows are restless during farrowing. To investigate whether gilts housed indoors would use branches for nest building and whether access to branches would affect the termination of nest building and parturient behaviour, we studied gilts housed individually in pens designed to stimulate natural nest building. The control group (n=21) had unlimited access to straw and the experimental group (n=21) had unlimited access to straw and branches. During nest building all the gilts used straw and all the experimental gilts also used branches. In the experimental group the interval from termination of nest building to birth of the first piglet (BFP) was significantly longer than in the control group (132 versus 58 min, P=0.04). In the experimental group, nest-building behaviour was also performed by fewer individuals during the interval from BFP until 2 h after than in the control group (38% versus 71% of the gilts, P=0.03). Gilts that performed nest building during this interval carried out more postural changes (P<0.001) and spent less time in lateral recumbency (P=0.001) than gilts which did not perform nest building. On average, gilts that performed nest building behaviour after BFP (n=26) spent 54% of the first 2 h of parturition in lateral recumbency and carried out 16 postural changes. Gilts that did not perform nest building behaviour during this interval (n=16) spent 85% of the time in lateral recumbency and carried out five postural changes. In 10 gilts that were selected randomly from the experimental group nest building was studied in more detail. In these gilts nest building peaked between 17 and 6 h prepartum. There was no difference in amount of behaviour directed towards straw and amount of behaviour directed towards branches.The results indicate that the termination of nest building in sows is under environmental feedback control. When only straw was provided the nests did not have much of a lasting structure. However, when gilts had access to straw and branches more structured and functional nests could be built. These nests may have been more effective in reducing the motivation for nest building prior to the onset of parturition.

A simplified technique for non-surgical catheterization of the vena cava cranialis in pigs and an evaluation of the method.

Restraint and venepuncture affect blood parameters and are stressful for pigs. Therefore, when experiments require frequent blood sampling, catheterization is the best option, both ethically and scientifically. A simplified non-surgical method for catheterization of the vena cava cranialis in sows is described. The vena cava is catheterized via the vena jugularis externa, which is punctured while the sow is restrained by nose snaring. The procedure can be carried out by two experimenters in 5 min, it requires little equipment and can be performed under farm or very simple experimental conditions. Results from 89 catheterizations are reported. Seventy-three of the catheters remained functional for 5 days or more. There was a tendency for a higher success rate in dry sows than in highly pregnant sows. The only behavioural effect observed after catheterization was a short-lasting increase in motivation for wallowing in some sows. No illness that could be attributed to the catheterization occurred.

Temporal differences in the responses of the pituitary adrenocortical axis, the sympathoadrenomedullar axis, heart rate, and behaviour to a daily repeated stressor in domestic pigs.

In this study we examined responses of domestic pigs (Sus scrofa domestica) to a daily repeated stressor. In particular, we focused on differences in temporal changes across treatment repetition between the pituitary adrenocortical axis, the sympathoadrenomedullar axis, heart rate, and behaviour. To induce a stress response, we separated eight castrated male pigs from their group mates visually and auditorily for 1 h on 10 successive days. Overall, enhanced plasma levels of cortisol, ACTH, and adrenaline indicated a clear stress response. Levels of cortisol and ACTH decreased continuously with repetition of exposures to the stressor. In contrast, levels of adrenaline, behavioural activity, and heart rate did not change consistently across repetition of exposures. Interestingly, therefore, hormones of the pituitary adrenocortical axis showed a process of adaptation whereas subjects did not adapt to the stressor with respect to titres of adrenaline, heart rate, and particular behaviours (e.g., grid pressing, vocalisation, locomotion). Instead, they continued to react actively towards the social separation. Our results suggest that different stress systems can differ in temporal pattern of their response towards a repeated stressor. Such temporal differences should be considered when studying the effects of repeated stress.

Behavior of laboratory animals under unnatural conditions.

Domestic animals are animals whose living conditions and reproduction, among other things, are controlled by man. As such, the current discussion about the welfare of domestic animals is similar for farm, companion, laboratory, and zoo animals. It concerns identification of the behavioral and physiological needs of the animals and development of living conditions that enable them to satisfy these needs. The paper describes two approaches that have been used in behavior biology to identify such needs. One approach is the measurement of stress responses that may be activated when an animal's needs are not fulfilled. The other approach is the use of operant conditioning techniques to establish demand functions by which the motivation of an animal to perform a specific behavior is measured. It is concluded that, since welfare is characterized by the absence of a number of factors, such as stress, pain, fear, disease, hunger etc., many types of measurements must be applied to ensure optimal welfare.

Dairy calves' discrimination of people based on previous handling.

To determine whether calves can distinguish between different people, we examined their contact with familiar and unfamiliar people and with people who handled them positively or aversively. When a familiar or unfamiliar person entered the calves' pens, latency to contact and duration of contact were the same, but bouts of contact were shorter and more frequent if the person was unfamiliar. In Exp. 2, calves were treated repeatedly in their home pens, by three handlers: one treated them positively, one aversively, and a third (neutral) did not interact with them. After seven treatments, calves tended to avoid all three handlers. After 12 treatments, calves contacted the positive handler significantly more than the aversive handler in their home pens. However, when retested outside their home pens, the calves did not discriminate. In Exp. 3, calves were treated positively and aversively in a novel treatment pen rather than in their home pens. The calves made more contact with the positive handler than the aversive handler after seven treatments. When retested in their home pens, most of the calves continued to avoid the aversive handler, but some made contact with the aversive handler. Calves can readily discriminate between different people based on their previous experience. They can develop a general fear of people as a result of aversive handling, and positive handling is required to overcome this. However, some calves do not generalize their fear of an aversive handler to places other than those in which they were handled.

Intermittent stress in pigs: effects on behavior, pituitary-adrenocortical axis, growth, and gastric ulceration.

Ninety-six pigs, half females and half castrated males from 12 litters, were housed in 24 groups of four litter mates. From an age of 115 days half of the groups were subjected to chronic stress for 33 days consisting of a schedule of unpredictable, inescapable electroshocks, and half served as controls. Behavior and performance were measured on all animals in the group, hormone data on one female in each group, and data on ulceration on the castrates. Behaviorally, the pigs did not habituate to 31 days of stress treatment. One to 2 days of stress treatment produced a behavioral activation that after 9 to 10 days was restricted to the time period of potential stress treatment. After 30 to 31 days it was replaced by passive behavior. In the beginning as well as after 30 to 31 days of intermittent stress, time spent sitting was increased. In addition, 6 days of intermittent stress reduced the baseline mean of plasma ACTH. After 33 days of stress the baseline mean of plasma ACTH was normalized, but the time course of diurnal secretion of ACTH was shifted. No effects of the chronic intermittent stress on basic levels of plasma cortisol, performance, or gastric ulceration were evident. In conclusion, the effect of intermittent stress depends on the number of days of intermittent stress treatment and it does not inevitably include changes in the basic levels of cortisol. Thus, assessment of stress must be based on a wide range of variables describing the process.

[Clinical chemical and hematological blood values and adaptation reactions in suckling calves in the first weeks of life]. / Klinisch-chemische und hämatologische Blutwerte und Anpassungsreaktionen bei Saugkälbern in den ersten Lebenswochen.

Suckler calves of the mother cow herd were used for this investigation. Body weight, growth rate and venous blood acid base status, gas content, creatinine, urea, lactate, total protein, albumin, Ca, Mg, Na, K and Cl were measured at 20, 60 and 90 days of postnatal life. Body weight and growth rate showed strong correlations with some blood values especially at 60 and 90 days of age meaning that adaptation is performed successful in some calves and incomplete in others. Disproportionate growth of body parts and the limited oxygen-carrying capacity below the oxygen needs of the tissues may cause the great lactate values in some calves of all age groups.

[Adaptation reaction of dairy calves in the first days of life. Effects of type of delivery and individuality of the newborn]. / Anpassungsreaktionen von Milchrindkälbern in den ersten Lebenstagen. Einflüsse durch Geburtsverlauf und individuelle Regelbreite.

Surveying a calving period of tethered dairy cows, newborn dairy calves of different breeds were investigated just after birth and at 24 hours and 48 hours of their postnatal life as well. Blood samples taken by venipuncture in calves were analyzed for acid-base-balance, hemoglobin, catecholamine and cortisol. Comparing the mean values of the newborns from calvings without assistance, with slight pulling and with heavy pulling, differences could be found only in the first hours of postnatal life between some of them without hemoglobin content of the blood that was of individually specificity and all the time lowest in calves delivered by heavy traction. Great scattering of and strong relationship between some of the measured values are assessed on the basis of constitutional features, maturity and adaptability of the calves.

[Reactions of heifers in early pregnancy and their offspring delivered at term by cesarean section and in the first postpartum days in a cow-calf operation]. / Reaktionen frühzeitig trächtiger Jungrinder und ihrer Nachkommen bei termingerechter Schnittentbindung und in den ersten postpartalen Lebenstagen in Mutterkuhhaltung.

In 11 heifers originating from one mother cow herd and in their offspring delivered by cesarean section heart rate recordings were taken during their staying in the calving box and later on in group housing. Heart rate showed a rhythmicity in accordance with behavioural physiological reactions. The mean heart rate of a 24 hour period in an animal was different between and within the newborn and elder animals. The mean heart rate was increasing in the calves during the first days of their postnatal life and decreasing in the mother cows within some days after parturition. Blood samples taken repeatedly in 9 heifers via an indwelling catheter and in their offspring short after birth and at 24 and 48 hours by venipuncture as well were analysed for acid-base status, cortisol, noradrenaline, adrenaline, hemoglobin and lactate. Comparing the results with other investigations can be used for evaluating the strain of delivery by cesarean section for the young and the mother as well as revealing main influences on the reactions of the animals and their individual specificity.

[Heart rate frequency and constitutional features of high yielding dairy cows in intensively managed and environmentally protected pasture]. / Herzschlagfrequenz und konstitutionelle Merkmale von Hochleistungsmilchrindern auf intensiv und umweltschonend bewirtschafteter Weide.

The heart rate measured continuously in grazing cows over 24 hours is significantly different during specific behavioural patterns of an animal and is influenced by the stage of pregnancy of the cow. Repeated measurements of blood urea, creatinine, total protein, albumin and glucose concentration in these animals permit conclusions about the changes of body weight and of the liver function and hormonal integration of energy substrate supply. Living on pasture during the summer period the cows showed the lowest hemoglobin content and hematocrit level of the blood, which increased when the animals were housed in autumn or when near the end of their final trimester of pregnancy. Important differences, especially in the blood values, were found between the groups and within the groups between younger and older cows.

[The hemoglobin concentration in the blood of dairy cattle of different breeds and their offspring during the peripartum period]. / Bemerkungen zur Hämoglobinkonzentration des Blutes bei Milchrinden verschiedener Rassen und bei ihren Nachkommen im peripartalen Zeitraum.

Blood samples taken repeatedly from dairy cows on pasture (50 Holstein-Friesian) and then from 181 cows and their newborn calves within 5 to 10 min after birth were used for measurement of haemoglobin content (Hb). Hb decreased with ongoing lactation and pregnancy, increased several weeks before parturition and reached its highest value shortly after birth. There was some individual, breed and age specificity of Hb in dairy cows. Assisted calvings using marked traction resulted in no difference in Hb values of the cows when compared to other calvings; whereas the calves' Hb values were smaller and the difference between calf Hb and cow Hb was greater. A strong correlation between Hb of the cow and Hb of the newborn calf and the difference Hb calf-Hb cow could be found.

[Cortisol determination before and after surgical treatments and associated methods in young pigs]. / Cortisolbestimmungen vor und nach chirurgischen Eingriffen sowie operationsbegleitenden Massnahmen bei Läuferschweinen.

138 weaned pigs have been examined for clinical and immunological parameters as well as cortisol from the day before to eight days after surgery (scrotal-hernias, cryptorchidisms). Important alterations in cortisol concentrations were found neither by the surgical intervention itself nor by accompanying measures like food restraint (48 hours), diagnostic blood sampling (venipuncture) and infectious prophylaxis (chemoprophylaxis, para-immunization). Therefore, chronically pathological stress reactions following routine surgical interventions may be excluded. Single elevations of serum cortisol above the physiological range (8-60 ng/ml) on the day after surgery without typically clinical stress symptoms and correlations to the cell mediated immunity may be interpreted as positive physiological stress reactions in connection with an elevated efficiency.

Opioid modulation of the effects of repeated stress on ACTH, cortisol, prolactin, and growth hormone in pigs.

Prepubertal gilts (n = 16) were restrained with a nose snare for 15 min each day over 9 days. At the beginning of the first and last nose snare, the animals were also injected IV with 1 mg/kg of naloxone. Blood samples were taken before and after restraint at 15-min intervals and plasma assayed for ACTH, cortisol, prolactin, and GH. The initial restraint led to significant increases in ACTH, cortisol, prolactin, and GH concentrations. There was no evidence of a reduction in the magnitude of endocrine responses with repeated restraint. Indeed, the response of GH was more apparent after the final restraint. In the absence of the restraint, naloxone elevated cortisol and ACTH concentrations. Naloxone, given with the first restraint, enhanced the increase in ACTH, cortisol, and prolactin. Naloxone, given during the last restraint, inhibited the increase in GH, but had less effect upon cortisol and prolactin concentrations than during the initial restraint. Gilts genetically selected for a high cortisol response to ACTH injections had a higher basal cortisol concentration and a higher cortisol response to restraint than gilts selected for a low cortisol response to ACTH. However, there were no differences between these groups in ACTH, prolactin, or GH concentrations, or in any endocrine response to naloxone. Endogenous opioids can inhibit pituitary-adrenocortical responses and enhance GH responses of pigs to stress. Measures of cortisol concentrations are poor predictors of prolactin and GH responses to stress.