Abnormal plasma neuroactive progestagen derivatives in ill, neonatal foals presented to the neonatal intensive care unit

Longitudinal assessment of adrenocortical steroid and steroid precursor response to illness in hospitalized foals

Sepsis is a major cause of morbidity and mortality in neonatal foals. Relative adrenal insufficiency (RAI), defined as an inadequate cortisol response to stress, has been associated with sepsis, prematurity, and poor outcome in newborn foals. In addition to cortisol, the adrenal gland synthesizes several biologically important steroids and steroid precursors, including aldosterone, androgens, and progestogens. However, concentration of these hormones during hospitalization and their association with the severity of disease and mortality in critically ill foals have not been completely evaluated. We hypothesized, that in addition to cortisol and aldosterone, concentration of steroid precursors (progestogens and androgens) will be altered in critically ill foals. We also proposed that septic foals will have higher concentrations of steroid precursors than healthy foals, and steroid concentrations will be persistently increased during hospitalization in non-surviving septic and premature foals. Foals <4 days of age were categorized as healthy, septic, sick non-septic, and premature based on physical exam, medical history, and laboratory data. Blood samples were collected on admission (0 h), 24 h, and 72 h after admission. Concentrations of steroids and ACTH were measured by immunoassays. The area under the curve over 72 h (AUC0-72h) of hospitalization was calculated for each hormone. Serum cortisol, aldosterone, progesterone, pregnenolone, dehydroepiandrosterone sulfate (DHEAS), and 17 α-hydroxyprogesterone concentrations were higher in septic and premature foals compared to healthy foals at 0 h and throughout 72 h of hospitalization (P < 0.05). Plasma ACTH concentrations were higher in septic and premature foals on admission compared to healthy controls (P < 0.05). The progesterone (AUC0-72h) cut-off value above which non-survival could be reliably predicted in hospitalized foals was 1,085 ng/mL/h, with 82% sensitivity and 77% specificity. Critically ill neonatal foals had an appropriate response to stress characterized by increased concentrations of cortisol and steroid precursors on admission. A rapid decline in steroid concentration was observed in healthy foals. However, persistently elevated progestogen and androgen concentrations were associated with a lack of improvement in the course of disease and poor outcome.

Postnatal Dynamics of Circulating Steroid Hormones in Mule and Equine Neonates

It is necessary to study hormonal patterns from mules to recognize alterations and neonatal maladaptation. Our objective was to evaluate concentrations of hormones in mule (n = 6) and equine foals (n = 6). Blood was collected at T0, 1, 6 and 12 h after birth. Hormone concentrations were evaluated using liquid chromatography tandem mass spectrometry. Effects of time, group and interactions and regression analysis were evaluated (p < 0.05). There was a cubic and quadratic decline in mule and equine foals, respectively, for 3β,20α-dihydroxy-DHP. Mule foals were born with lower circulating 3β,20α-dihydroxy-DHP concentrations, which might be related to progestogen concentrations in mares with a hybrid placenta. Corticosterone and cortisol concentrations remained unchanged for the first hour post-foaling then declined in mule and equine foals (p < 0.0001). Dehydroepiandrosterone was the main androgen present. There was a decrease in dihydrotestosterone at 12 h (p = 0.002). Differences in the temporal patterns of secretion within each steroid class, pregnanes, corticoids, and androgens, suggest they were derived from different tissue sources, presumptively the placenta, adrenals and gonads of the fetus/neonate, respectively. Mule and horse foals were born without evidence of testosterone secretion. For the first time, steroid hormone levels were measured in neonatal mules, and this will provide insight into neonatal physiology that differs from equine and allow us to gain an understanding of mules that have rarely been studied. Further studies are needed to elucidate the effects of hybrid pregnancies in the steroid endocrinology of neonates.

Neurologic Disorders of the Foal

Neurologic disease of foals is a diagnostic and therapeutic challenge for veterinarians. Disease conditions such as neonatal encephalopathy are seen as well as developmental and congenital defects, bacterial infections, and trauma. Neonatal encephalopathy can be considered a "syndrome" with a variety of causes resulting in a similar clinical presentation. These causes can be categorized as maladaptation, hypoxic/ischemic encephalopathy, and metabolic abnormalities, all leading to signs of cerebral and brainstem disease. Spinal cord signs may occasionally be seen, but these signs are usually overshadowed by cerebral disease. Treatment in most cases involves supportive care and outcome is favorable in most cases.

Characterisation of the Behavioural Effects of a Thoracic Squeeze in Healthy Newborn Piglets

Simple Summary

Firmly squeezing the chests of newborn foals and calves that are showing abnormal behaviours after birth causes them to enter a less-responsive state, characterised by lying down with eyes closed and no limb movements. Once the squeeze is removed, the newborns immediately ‘wake up’ and begin to display more normal behaviours. This response to the thoracic squeeze has also been observed in healthy, normally behaving foals. However, no studies have looked at the effects of the thoracic squeeze in healthy newborns of other mammalian species. We aimed to characterise the behavioural responses of healthy newborn piglets to a thoracic squeeze using the following two methods: a soft fabric rope, or a purpose-made inflation cuff. Behavioural data indicated that all piglets initially became less responsive, with reduced or absent reflex responses to a toe pinch or touch of the eyelid observed in over half of the piglets. The piglets squeezed with the inflation cuff appeared to enter a less-responsive state faster than the piglets squeezed with the rope. These findings suggest that the piglets responded to the thoracic squeeze in a similar way to healthy foals and that this may be a response conserved across multiple precocial mammalian species. Furthermore, the squeeze was found to be safe for inducing a less-responsive state in healthy piglets. This study provides a foundation for exploring the mechanisms underlying the responses to the thoracic squeeze and potential applications whilst performing husbandry procedures.

Abstract

A thoracic squeeze has been observed to cause both healthy and low vigour neonatal foals to enter a ‘less-responsive state’, characterised by loss of posture, eye closure and cessation of movement, from which they rapidly recover to express normal healthy behaviours when the squeeze is released. To date, there have been no systematic studies characterising the responses of healthy neonates of other mammalian species to a thoracic squeeze. We describe the responses of healthy newborn piglets (n = 17) to a standardised application of the thoracic squeeze and evaluate the effect of the method of squeeze application on the response. Neonatal piglets were squeezed around the chest with either a soft fabric rope as has been used in foals (n = 8) or a novel purpose-made inflation cuff (n = 9). Both methods were effective at inducing a less-responsive behavioural state in all piglets, with neural reflexes reduced or absent in over half of them. The inflation cuff appeared to induce the less-responsive state faster than the rope, and more piglets squeezed with the cuff remained in this state for the full 10-min squeeze. These findings suggest that the behavioural response of foals to thoracic squeezing can be generalised to neonates of other precocial mammalian species. This initial study provides a foundation for further research using the inflation cuff to explore mechanisms underlying the thoracic squeeze and ways in which it may be applied whilst performing husbandry procedures.

Adrenal Gland Ultrasonographic Measurements and Plasma Hormone Concentrations in Clinically Healthy Newborn Thoroughbred and Standardbred Foals

Simple Summary

The hypothalamic–pituitary–adrenal axis regulates many physiologic and metabolic functions and plays a central role in the inflammatory response to illness. Clinically, hypothalamic–pituitary–adrenal axis function can be evaluated by combined assessment of adrenal hormones, adrenocorticotropin plasma concentrations and ultrasonographic examination of the adrenal glands in other species. Multiple individual variables have been demonstrated to affect ultrasonographic measurements of adrenal glands in several species. Ultrasonographic measurements of the adrenal glands and plasma concentration of adrenocorticotropin, cortisol, dehydroepiandrosterone, progesterone, aldosterone and adrenocorticotropin/adrenal hormone ratios were assessed and compared between Thoroughbred and Standardbred healthy neonatal foals. The effect of age, weight and sex on ultrasonographic measurements of the adrenal glands was also investigated. The width of whole adrenal glands and the medulla differed significantly between Thoroughbreds and Standardbreds. Cortisol and adrenocorticotropin were, respectively, higher and lower in Thoroughbreds than in Standardbreds. The cortisol/dehydroepiandrosterone ratio was higher in Thoroughbreds than in Standardbreds. The results of this study provide reference ranges for healthy neonatal Thoroughbred and Standardbred foals and suggest the presence of breed-related differences in ultrasonographic measurements, plasmatic cortisol and adrenocorticotropin concentrations. The higher cortisol/dehydroepiandrosterone ratio of Thoroughbred foals may suggest a different response to stress and environmental stimulation between the two breeds.

Abstract

Adrenal hormones, ACTH plasma concentrations and the ultrasonographic evaluation of the adrenal glands are considered complementary in clinical evaluations of the hypothalamic–pituitary–adrenal (HPA) axis function in several species. In dogs, age, size and weight have a significant effect on the ultrasonographic size of the adrenal glands. In neonatal foals, ultrasonographic evaluation and measurements of the adrenal glands have been demonstrated to be reliable; however, the effect of individual variables on ultrasonographic features has not been investigated, and the clinical usefulness of adrenal gland ultrasonography is still not known. The aims of this study were: (i) to provide and compare adrenal glands ultrasound measurements in healthy newborn Thoroughbred and Standardbred foals, and assess any effect of age, weight and sex on them; (ii) to assess and compare ACTH and steroid hormone concentrations in healthy neonatal foals of the two breeds. Venous blood samples and ultrasonographic images of the adrenal glands were collected from 10 healthy neonatal Thoroughbred and 10 healthy neonatal Standardbred foals. Ultrasonographic measurements of the adrenal glands were obtained and adrenocorticotropin (ACTH), cortisol, dehydroepiandrosterone (DHEA), progesterone (P4) and aldosterone plasma concentrations were assessed. The ACTH/cortisol, ACTH/progesterone, ACTH/aldosterone, ACTH/DHEA and cortisol/DHEA ratios were calculated. A significant positive correlation was found between the height of the right adrenal gland and the foal’s weight; the width of the right and left adrenal gland and the medulla was significantly lower in Thoroughbreds than in Standardbreds. Cortisol and ACTH plasma concentrations were significantly higher and lower, respectively, in Thoroughbreds compared with Standardbreds. The cortisol/DHEA ratio was significantly higher in Thoroughbreds. This study provides reference ranges for neonatal Thoroughbred and Standardbred foals, and suggests the presence of breed-related differences in ultrasonographic adrenal gland measurements, plasmatic cortisol and ACTH concentrations. The higher cortisol/DHEA ratio detected in Thoroughbred foals could suggest a different response to environmental stimulation in the two breeds.

Dynamics of androgens in healthy and hospitalized newborn foals

Background

Information on steroids derived from the adrenal glands, gonads, or fetoplacental unit is minimal in newborn foals.

Objective

To measure androgen concentrations in serum and determine their association with disease severity and outcome in hospitalized foals.

Animals

Hospitalized (n = 145) and healthy (n = 80) foals.

Methods

Prospective, multicenter, cross‐sectional study. Foals of ≤3 days of age from 3 hospitals and horse farms were classified as healthy and hospitalized (septic, sick nonseptic, neonatal maladjustment syndrome [NMS]) based on physical exam, medical history, and laboratory findings. Serum androgen and plasma ACTH concentrations were measured with immunoassays. Data were analyzed by nonparametric methods and univariate analysis.

Results

Serum dehydroepiandrosterone (DHEA), androstenedione, testosterone, and dihydrotestosterone (DHT) concentrations were higher upon admission in hospitalized foals (P <  .05), were associated with nonsurvival, decreased to 4.9‐10.8%, 5.7‐31%, and 30.8‐62.8% admission values in healthy, SNS, and septic foals, respectively (P < .05), but remained unchanged or increased in nonsurviving foals. ACTH:androgen ratios were higher in septic and NMS foals (P < .05). Foals with decreased androgen clearance were more likely to die (odds ratio > 3; P < .05).

Conclusions and Clinical Importance

Similar to glucocorticoids, mineralocorticoids, and progestagens, increased serum concentrations of androgens are associated with disease severity and adverse outcome in hospitalized newborn foals. In healthy foals, androgens decrease over time, however, remain elevated longer in septic and nonsurviving foals. Androgens could play a role in or reflect a response to disorders such as sepsis or NMS in newborn foals.

Steroid precursors, steroids, neuroactive steroids, and neurosteroids concentrations in serum and saliva of healthy neonatal heifer Holstein calves

BACKGROUND

Persistence of high neurosteroid concentrations in blood is associated with neonatal encephalopathy and septicemia in foals. This has not been investigated in calves.

OBJECTIVES

To determine concentrations of steroid compounds in serum and saliva within the first 48 hours after birth in healthy neonatal calves, identify potential markers for disease, and investigate the association between serum steroid compounds concentrations in calves and their respective dams within 2 hours after birth.

ANIMALS

Twelve healthy neonatal heifer Holstein calves and their dams.

METHODS

Prospective study. Serum and saliva were collected from calves at 2, 6, 24, and 48 hours after birth. Steroid compounds were analyzed using liquid chromatography-mass spectrometry. A nonlinear regression model was used to determine half-lives of the neurosteroids. Serum concentrations of neurosteroids between the cows and calves were compared using the Wilcoxon signed rank test.

RESULTS

Half-lives (95% confidence intervals) of dehydroepiandrosterone (DHEA) and 17α,20α-dihydroxyprogesterone in calf serum were 2.9 (2.1, 4.3), and 2.1 (1.3, 3.0) hours, respectively. Pregnanediol in saliva had a half-life (95% confidence interval) of 24.5 (14.2, 66.5) hours. Serum DHEA (1718.7 ± 2313 vs 57.7 ± 44) and 17α,20α-dihydroxyprogesterone (207.8 ± 198.2 vs 43.5 ± 33.5) concentrations respectively were higher (P < .05) in calves compared to cows.

CONCLUSIONS AND CLINICAL IMPORTANCE

Dehydroepiandrosterone, 17α,20α-dihydroxyprogesterone, and pregnanediol could be potential markers of disease in neonatal heifer calves with unexplained failure to thrive or encephalopathy. However, because of the wide 95% confidence interval of the half-life, pregnanediol in saliva might not be a potential marker.

Do Dehydroepiandrosterone (DHEA) and Its Sulfate (DHEAS) Play a Role in the Stress Response in Domestic Animals?

In animal husbandry, stress is often associated with poor health and welfare. Stress occurs when a physiological control system detects a state of real or presumptive threat to the animal's homeostasis or a failure to control a fitness-critical variable. The definition of stress has mostly relied on glucocorticoids measurement, even though glucocorticoids represent one stress-response system, the hypothalamus-pituitary-adrenocortical axis, which is not precise enough as it is also related to metabolic regulation and activated in non-stressful situations (pleasure, excitement, and arousal). The mammal adrenal can synthesize the androgenic steroid dehydroepiandrosterone (DHEA) and its sulfate metabolite (DHEAS), which have been associated to the stress response in several studies performed mostly in humans and laboratory animals. Although the functions of these steroids are not fully understood, available data suggest their antagonistic effects on glucocorticoids and, in humans, their secretion is affected by stress. This review explores the scientific literature on DHEA and DHEAS release in domestic animals in response to stressors of different nature (inflammatory, physical, or social) and duration, and the extra-adrenal contribution to circulating DHEA. Then, the potential use of DHEA in conjunction with cortisol to improve the definition of the stress phenotype in farmed animals is discussed. Although the focus of this review is on farmed animals, examples from other species are reported when available.

Relationship between postpartum uterine involution and biomarkers of inflammation and oxidative stress in clinically healthy mares (Equus caballus)

To test the hypothesis that delayed/impaired uterine involution could be associated with oxinflammation, we studied the progression of the uterine involution in association with some biomarkers of inflammation and oxidative stress in clinically healthy mares (N = 26) during early postpartum. The examination of the reproductive tract was performed on Days 7 and 21 after foaling. Uterine involution was assessed considering: a) the increase of the gravid uterine horn diameter (GUHD) compared with diameter recorded before pregnancy during the previous breeding season; b) the level of endometrial edema (EE); c) the degree of accumulation of intrauterine fluid (IUFA); d) the status of the cervix (CS). Inflammation and oxidative stress were studied by measuring serum amyloid A (SAA), cortisol, DHEA, AOPP, protein carbonyl groups, malondialdheyde (MDA) and thiols in plasma on Days 7 and 21. By Day 21 after parturition, a significant improvement (P < 0.01) was observed for GUHD and EE; while IUFA increased in six animals. Plasma SAA and DHEA concentrations were higher when the clinical parameters indicated a lower degree of uterine involution. On Day 7, the cortisol/DHEA ratio was lower in animals with higher degree of EE. Plasma AOPP and MDA concentrations were significantly lower (P < 0.05) in animals with the lower GUHD. On Day 21, plasma MDA concentrations were significantly lower (P < 0.05) in animals with the lower IUFA. Our data suggest that a mild condition of inflammation and oxidative stress occur in mares with delayed/impaired uterine involution.

Potential benefit of a thoracic squeeze technique in two newborn calves delivered by caesarean section

Case History: Two calves delivered following elective caesarean section showed behaviour typical of neonatal maladjustment syndrome described in foals, i.e., indifference to environmental stimuli, lack of affinity for the dam, failure to find the udder, refusal to suck, aimless wandering or motionless standing. Calves were subjected to a clinical examination immediate after delivery and there were no signs of defects, illness, pain, dehydration, hypoxia, acidaemia or other causes for the unresponsive behaviour.Clinical Findings and Treatment: Both calves were subjected to the thoracic squeeze technique, one at 6 hours and the other at 20 hours after delivery. A soft rope was looped around the thorax and gentle pressure was applied to the free end of the rope, squeezing the calf's chest for 20 minutes. Both calves exhibited a sleep-like state manifested by closed eyes, no body movements, slow breathing and a decrease in heart rate, for the entire squeezing period. When the rope was removed the calves woke up immediately, rose and walked towards the dam. When led to the dam's udder, the weaker calf began to suck. Both were reported, by the stockperson, to follow the dam and suck normally the following day.Clinical Relevance: Provided all other disease processes are excluded, very young calves that exhibit indifference to environmental stimuli and lack of affinity for the dam may be good candidates for application of the thoracic squeeze technique that has been demonstrated to have clinical efficacy in foals with neonatal maladjustment syndrome.

Plasma concentrations of steroid precursors, steroids, neuroactive steroids, and neurosteroids in healthy neonatal foals from birth to 7 days of age

BACKGROUND

Transient hypothalamic-pituitary-adrenal axis dysfunction occurs in critically ill foals with sepsis and neonatal maladjustment syndrome (NMS). Cortisol is the most commonly measured steroid. However, a complex interaction of various steroid compounds might play a role in pathophysiology of this disorder.

OBJECTIVE

To identify steroid compounds present at high concentrations at birth that rapidly and steadily decrease within the first 7 days of life in healthy foals and that might be supportive diagnosis of NMS and other neonatal disorders.

ANIMALS

Ten healthy neonatal Quarter Horse foals (5 females and 5 males).

METHODS

Prospective study. Blood was collected in heparinized tubes within 30 minutes after birth, and at 12, 24, 48, 72, 96, 120, 144, and 168 hours of age. Plasma was separated and a panel of steroid compounds was analyzed using liquid chromatography-mass spectrometry. A nonlinear regression model was used to determine decay concentrations over time. Confidence intervals (CIs) were calculated and significance was set a P ≤ .05.

RESULTS

Five compounds were identified: pregnenolone, progesterone, deoxycorticosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate. Pregnenolone and progesterone concentrations rapidly decreased by 24 hours of age and remained low throughout the first 7 days of life. Their half-life (95% CI) was short at 3.7 (3.4, 4.0) and 4.5 (2.8, 6.1) hours, respectively. No statistical differences in the concentrations of these compounds were found between males and females.

CONCLUSIONS AND CLINICAL RELEVANCE

Progesterone might be a useful marker for identifying continuous endogenous production of neuroactive steroids in foals with suspected NMS and other neonatal diseases.

Multiple adrenocortical steroid response to administration of exogenous adrenocorticotropic hormone to hospitalized foals

Background

The hypothalamic‐pituitary‐adrenal axis regulates the response to sepsis‐associated stress. Relative adrenal insufficiency or adrenocorticotropic hormone (ACTH):cortisol imbalance, defined as a poor cortisol response to administration of ACTH, is common and associated with death in hospitalized foals. However, information on other adrenal steroid response to ACTH stimulation in sick foals is minimal.

Objective

To investigate the response of multiple adrenocortical steroids to administration of ACTH in foals.

Animals

Hospitalized (n = 34) and healthy (n = 13) foals.

Methods

In this prospective study, hospitalized foals were categorized into 2 groups using cluster analysis based on adrenal steroids response to ACTH stimulation: Cluster 1 (n = 11) and Cluster 2 (n = 23). After baseline blood sample collection, foals received 10 μg of ACTH with additional samples collected at 30 and 90 minutes after ACTH. Steroid and ACTH concentrations were determined by immunoassays. The area under the curve (AUC) and Delta_0‐30 were calculated for each hormone.

Results

The AUC for cortisol, aldosterone, androstenedione, pregnenolone, 17α‐OH‐progesterone, and progesterone were higher in critically ill (Cluster 1) compared to healthy foals (P < .01). Delta_0‐30 for cortisol and 17α‐OH‐progesterone was lower in Cluster 1 (24%, 26.7%) and Cluster 2 (16%, 11.2%) compared to healthy foals (125%, 71%), respectively (P < .05). Foals that died had increased AUC for endogenous ACTH (269 versus 76.4 pg/mL/h, P < .05) accompanied by a low AUC for cortisol (5.5 versus 15.5 μg/dL/h, P < .05), suggesting adrenocortical dysfunction.

Conclusion and Clinical Importance

The 17α‐OH‐progesterone response to administration of ACTH was a good predictor of disease severity and death in hospitalized foals.

Equine Neonatal Encephalopathy: Facts, Evidence, and Opinions

Neonatal encephalopathy (NE) and neonatal maladjustment syndrome (NMS) are terms used for newborn foals that develop noninfectious neurologic signs in the immediate postpartum period. Cerebral ischemia, hypoxia, and inflammation leading to neuronal and glial dysfunction and excitotoxicity are considered key mechanisms behind NE/NMS. Attention has been placed on endocrine and paracrine factors that alter brain cell function. Abnormal steroid concentrations (progestogens, neurosteroids) have been measured in critically ill and NE foals. In addition to supportive treatment, antimicrobials should be considered. Controversies regarding the pathophysiology, diagnosis, and treatment of NE and NMS will remain until controlled mechanistic and therapeutic studies are conducted.

Neonatal Encephalopathy in Calves Presented to a University Hospital

BACKGROUND

While studies have examined bovine dystocia in relation to calf survival, little has been published regarding perinatal morbidity and treatment of newborn calves beyond failure of transfer of passive immunity (FTPI). Neonatal encephalopathy (NE) is a clinical syndrome commonly diagnosed in infants and foals but is poorly described in calves.

HYPOTHESIS/OBJECTIVES

To identify risk factors for development of NE in calves and factors predictive of survival.

ANIMALS

Neonatal calves presented to a University hospital over a 10-year period.

METHODS

Retrospective cohort study (2005-2015). Medical records of all neonatal calves presented to the hospital were examined, and cases of NE were identified. Data pertaining to demographics, dam parity, labor, treatment, and outcome were collected and analyzed with univariate and multivariate statistics.

RESULTS

Of 200 calves in the final analysis, 58 (29%; 95% CI: 22.8-35.8%) were classified as NE and 142 calves as non-NE. In univariate analysis, factors significantly associated with diagnosis of NE included male sex, presence of dystocia, abnormal position in the birth canal, and prolonged labor. In the multivariate model, only orientation of the calf in the birth canal remained significant (OR 2.14; 95% CI: 1.02-4.49; P = 0.044). Overall survival of calves with NE was good (45/58; 77.6%; 95% CI: 64.7-87.5); dam parity and being a twin was significantly associated with nonsurvival.

CONCLUSIONS

Calves born after dystocia, especially if malpresented, should be closely monitored for nursing behavior within the first 24 hours of life. Prognosis for survival is good, but supportive care might be required for several days.

Survey of Veterinarians Using a Novel Physical Compression Squeeze Procedure in the Management of Neonatal Maladjustment Syndrome in Foals

Horses are a precocious species that must accomplish several milestones that are critical to survival in the immediate post-birth period for their survival. One essential milestone is the successful transition from the intrauterine unconsciousness to an extrauterine state of consciousness or awareness. This transition involves a complex withdrawal of consciousness inhibitors and an increase in neuroactivating factors that support awareness. This process involves neuroactive hormones as well as inputs related to factors such as cold, visual, olfactory, and auditory stimuli. One factor not previously considered in this birth transition is a yet unreported direct neural reflex response to labor-induced physical compression of the fetus in the birth canal (squeezing). Neonatal maladjustment syndrome (NMS) is a disorder of the newborn foal characterized by altered behavior, low affinity for the mare, poor awareness of the environment, failure to bond to the mother, abnormal sucking, and other neurologically-based abnormalities. This syndrome has been associated with altered events during birth, and was believed to be caused exclusively by hypoxia and ischemia. However, recent findings revealed an association of the NMS syndrome with the persistence of high concentrations of in utero neuromodulating hormones (neurosteroids) in the postnatal period. Anecdotal evidence demonstrated that a novel physical compression (squeeze) method that applies 20 min of sustained pressure to the thorax of some neonatal foals with this syndrome might rapidly hasten recovery. This survey provides information about outcomes and time frames to recovery comparing neonatal foals that were given this squeeze treatment to foals treated with routine medical therapy alone. Results revealed that the squeeze procedure, when applied for 20 min, resulted in a faster full recovery of some foals diagnosed with NMS. The adjunctive use of a non-invasive squeeze method may improve animal welfare by hastening recovery and foal-mare interactions that minimize health problems. This would also avoid or reduce costs arising from hospitalization associated with veterinary and nursing care that sometimes leads owners to elect for euthanasia.

Ultrasonographic assessment of the atlanto-occipital space in healthy Thoroughbred foals and Thoroughbred foals with neonatal maladjustment syndrome

Ultrasonography of the atlanto-occipital (AO) space may be useful as a non-invasive diagnostic tool in neonatal foals. The aims of the study were establish a range of values for ultrasonographic measurements of the AO space in healthy Thoroughbred foals and to compare these variables in healthy foals with foals diagnosed with neonatal maladjustment syndrome (NMS). Ultrasonography of the AO space was performed on 38 healthy Thoroughbred foals and 28 Thoroughbred foals with NMS≤4days of age. Transverse image spinal cord height (P=0.001), width (P<0.001) and spinal cord cross sectional area (P<0.001), and longitudinal image dorsoventral diameter of the ventral spinal artery, were significantly smaller in foals with NMS than in healthy foals. Ratios of spinal canal to cord width and cross sectional area were significantly smaller in healthy foals than in foals with NMS (P<0.001). Spinal canal variables were not significantly different between groups. Several ultrasonographic measurements of the AO space were significantly different between healthy foals and foals with NMS. Further investigation is warranted to investigate the clinical application of this technique.

Steroids, steroid precursors, and neuroactive steroids in critically ill equine neonates

Hypothalamic-pituitary-adrenal axis (HPAA) dysfunction has been associated with sepsis and mortality in foals. Most studies have focused on cortisol, while other steroids have not been investigated. The objectives of this study were to characterise the adrenal steroid and steroid precursor response to disease and to determine their association with the HPAA response to illness, disease severity, and mortality in hospitalised foals. All foals (n=326) were classified by two scoring systems into three categories: based on the sepsis score (septic, sick non-septic [SNS] and healthy) and the foal survival score (Group 1: 3-18%; Group 2: 38-62%; Group 3: 82-97% likelihood of survival). Blood concentrations of adrenocorticotropic hormone (ACTH) and steroids were determined by immunoassays. ACTH-cortisol imbalance (ACI) was defined as a high ACTH/cortisol ratio. Septic foals had higher ACTH, cortisol, progesterone, 17α-OH-progesterone, pregnenolone, and androstenedione concentrations as well as higher ACTH/cortisol, ACTH/progesterone, ACTH/aldosterone, and ACTH/DHEAS ratios than SNS and healthy foals (P<0.01). Foals with DHEAS of 0.4-5.4ng/mL were more likely to have ACI (OR=2.5). Foals in Group 1 had higher ACTH, aldosterone, progesterone, and cortisol concentrations as well as ACTH/cortisol, ACTH/progesterone, and ACTH/DHEAS ratios than foals in Groups 2 and 3 (P<0.01). High progesterone concentrations were associated with non-survival and the cutoff value below which survival could be predicted was 23.5ng/mL, with 75% sensitivity and 72% specificity. In addition to cortisol, the response to the stress of illness in foals is characterised by the release of multiple adrenal steroids. DHEAS and progesterone were good predictors of HPAA dysfunction and outcome in hospitalised foals.

Skin-to-skin contact after birth and the natural course of neurosteroid levels in healthy term newborns

OBJECTIVE

To determine the postnatal course of neurosteroid levels in relation to gender, mode of delivery and the extent of skin-to-skin (STS) contact during the first days of life in healthy term newborns.

STUDY DESIGN

Prospective observational study of 39 neonates in which parents recorded total duration of STS in the first 2 days and nine neurosteroids (dehydroepiandrosterone-sulfate, progesterone, pregnenolone, pregnenolone-sulfate, allopregnanolone, isopregnanolone, epipregnanolone, pregnanolone and pregnanolone-sulfate) were assayed from blood samples at birth and at 1-2 days of age.

RESULTS

All nine neurosteroid levels declined significantly during the first 2 days of life. Gender did not significantly affect the change in neurosteroid levels. The decline in neurosteroid levels was generally more pronounced in vaginal deliveries, and there was a trend toward a larger decline with more exposure to STS.

CONCLUSION

Ongoing studies may better characterize the role of neurosteroids and the influence of STS in more critically ill and premature neonates.

The dynamic steroid landscape of equine pregnancy mapped by mass spectrometry

Liquid chromatography–tandem mass spectrometry (LC–MS/MS) allowed comprehensive analysis of various steroids detectable in plasma throughout equine gestation. Mares (n=9) were bled serially until they foaled. Certain steroids dominated the profile at different stages of gestation, clearly defining key physiological and developmental transitions. The period (weeks 6–20) coincident with equine chorionic gonadotropic (eCG) stimulation of primary corpora lutea and subsequent formation of secondary luteal structures was defined by increased progesterone, 17OH-progesterone and androstenedione, all Δ4 steroids. The 5α-reduced metabolite of progesterone, dihydroprogesterone (DHP) paralleled progesterone secretion at less than half the concentration until week 12 of gestation when progesterone began to decline but DHP concentrations continued to increase. DHP exceeded progesterone concentrations by week 16, clearly defining the luteo-placental shift in pregnane synthesis from primarily ovarian to primarily placental. The period corresponding to the growth of fetal gonads was defined by increasing dehydroepiandrosterone and pregnenolone (Δ5 steroids) concentrations from week 14, peaking at week 34 and declining to term. Metabolites of DHP (including allopregnanolone) dominated the steroid profile in late gestation, some exceeding DHP by weeks 13 or 14 and near term by almost tenfold. Thus Δ4 steroids dominated during ovarian stimulation by eCG, inversion of the ratio of progesterone: DHP (increasing 5α-pregnanes) marked the luteo-placental shift, Δ5 steroids defined fetal gonadal growth and 5α-reduced metabolites of DHP dominated the steroid profile in mid- to late-gestation. Comprehensive LC–MS/MS steroid analysis provides opportunities to better monitor the physiology and the progress of equine pregnancies, including fetal development.

Antimicrobial use in critically ill horses

OBJECTIVE

To discuss controversies surrounding antimicrobial use in critically ill horses.

DATA SOURCES

PubMed searches from 1970-present for terms including, but not limited to: "horse," "foal," "antimicrobial," "prophylaxis," "infection," "surgery," "sepsis," and "antimicrobial resistance."

HUMAN DATA SYNTHESIS

Increasing bacterial antimicrobial resistance has changed first-line antimicrobial choices and prompted shortening of the duration of prophylactic and therapeutic treatment. The need to decrease bacterial resistance development to critically important antimicrobials has been highlighted.

VETERINARY DATA SYNTHESIS

Veterinary medicine has followed a similar trend but often without a high-level evidence. Common dilemmas include diseases in which the theoretically most effective drug is a reserved antimicrobial, the inability to differentiate infectious from noninfectious disease, the duration and necessity of prophylactic antimicrobials and use of antimicrobials in primary gastrointestinal disease. These problems are illustrated using examples of purulent infections, neonatal sepsis, colic surgery, and treatment of colitis. Although enrofloxacin, cephalosporins, and doxycycline, in contrast to gentamicin, reach therapeutic concentrations within the lungs of healthy horses, the first two should not be used as first line treatment due to their reserved status. Due to the high risk of bacterial sepsis, antimicrobial treatment remains indispensable in compromised neonatal foals but shortening the length of antimicrobial treatment might be prudent. One prospective randomized study demonstrated no difference between 3 and 5 days of perioperative antimicrobial treatment in colic surgery but shorter durations were not evaluated. High-level evidence to recommend antimicrobial treatment of adult horses with undifferentiated diarrhea does not exist.

CONCLUSIONS

Few evidence-based recommendations can be made. Commonly used antimicrobial combinations remain the mainstay for treating purulent infections. Antimicrobial treatment for compromised foals should not extend beyond recovery. Continuation of prophylactic antimicrobials >3 days is likely unnecessary after colic surgery; shorter durations might be equally effective. Antimicrobial prophylaxis in adult horses with diarrhea is unlikely to be beneficial.