bluuebunny/crossref_metadata_2025 huggingface dataset:
Prostaglandin release and luteolysis associated with physiological and pathological conditions of the reproductive cycle of the mare: a review
Authors: DAELS P. F. , STABENFELDT G. H. , KINDAHL H. , HUGHES J. P.
Published: June 2010

The advent of radioimmunoassay for the major metabolite of prostaglandin F2α(PGF2α), 15‐keto‐13, 14‐dihydro‐PGF2α(15‐ketodihydro‐PGF2α), has allowed the dynamics of PGF2α, secretion to be studied in a variety of physiological and pathological situations in domestic animals, including the mare. In the non‐pregnant cyclic mare, PGF2αis responsible for the regression of the corpus luteum. In the pregnant mare, pulsatile secretion of PGF2αis blocked by the presence of the conceptus and the corpus luteum continues to secrete progesterone, essential to the support of pregnancy. At term, the massive increase in PGF2αsynthesis is the major stimulus for uterine contractions during delivery. The endometrium of the non‐pregnant mare secretes PGF2αin response to inflammatory changes caused by bacterial infection, intra‐uterine infusion of saline (low pH) or other irritants; the amount of PGF2αreleased is often sufficient to initiate luteolysis. In the pregnant mare, stimuli that can initiate PGF2αsecretion by the endometrium include uterine and cervical manipulation, chronic uterine inflammation, surgical manipulation of the uterus in conjunction with removal of one of twin conceptuses and manual rupture of one embryonic vesicleper rectumin mares carrying twins. Prostaglandin F2αcan be released by tissues other than the uterus. Systemic administration of endotoxin will induce the synthesis and release of PGF2α. The secretion of PGF2αin this situation can result in a decrease of luteal function or complete luteolysis in both the non‐pregnant and pregnant mare. In mares less than 55 days pregnant, compromised luteal activity following the administration of endotoxin results in death of the conceptus. Ongoing studies indicate that flunixin meglumine, a non‐steroidal anti‐inflammatory drug, effectively blocks PGF2αsecretion and can be used to prevent embryonic death in the event of endotoxaemia. Altrenogest can be used as an alternative treatment for the prevention of embryonic death. To be effective, flunixin meglumine must be administered soon after the onset of endotoxaemia whereas altrenogest treatment can be initiated up to 12 h later and still prevent pregnancy loss.
Growth rates of male and female equine embryos between Days 6 and 15 of pregnancy
Authors: ROMAGNANO A. , BETTERIDGE K. J. , RICHER C. L. , SIROIS J. , KING W. A.
Published: June 2010

To see whether any indication could be found that male conceptuses might develop more rapidly than females in the horse, as they do in several other mammals, pre‐attachment growth rates of female and male conceptuses were estimated from composite curves derived from the diameters of 36 female and 39 male conceptuses each measured once when collected at known times between six and 15 days after ovulation. The conceptuses were sexed cytogenically during the course of a previously reported study. The overall rates of growth (increase in conceptus diameter) were not significantly different for males and females. However, on any given day there was great variation in size amongst embryos and much overlap between the sizes of males and females. It is concluded that comparison of the growth rates of individual embryos, obtained by repeated echographic measurements, might reduce this variability and be a more useful means of continuing this investigation.
The development of Polish ponies born after embryo transfer to large recipients
Authors: TISCHNER M. , KLIMCZAK M.
Published: June 2010

Embryos from Polish pony mares (387 to 400 kg) were transferred to larger draught‐type mares (561 to 780 kg). Upon confirmation of pregnancy in the recipients, the donor mares were mated again to the same stallions. Six pairs of full sibling foals were obtained from which three pairs with matching gender were selected for long‐term developmental studies. All the foals born to recipient draught mares were larger and heavier than their siblings born to the genetic mothers. They also developed more rapidly during the nursing period. After weaning, the differences between individuals of each pair gradually became less evident. However, even at 53 months of age, there were still distinct differences in height at the withers (4 to 6 cm), length of front legs (4 cm) and length of cannon bones (1 to 2 cm).
Use of two‐year‐old mares as embryo donors in a commercial embryo transfer programme
Authors: SAVAGE N. C. , WOODCOCK L. A. , de GANNES G.
Published: June 2010

In a commercial embryo transfer programme between 1985 and 1988, using two‐year‐old donor mares to achieve greater productivity and economic return, embryos were collected non‐surgically and transferred by transcervical technique. Embryo collection was performed on 19 mares on 31 occasions between 6.5 and 7.5 days post‐ovulation. Over the four years, 77.4 per cent (24 of 31) of the collections resulted in embryo recovery and there was no significant effect of year on recovery rate. Repeated recovery attempts in successive cycles showed no adverse effects on recovery rates. Using transcervical transfer, the pregnancy rate per recovery attempt was 12.9 per cent (range 10 to 57 per cent) and the pregnancy rate per transferred embryo was 30.4 per cent (range 14 to 80 per cent). Pregnancy data were calculated from ultrasound evaluations at 12 to 15, 20, 30, 45, 60 and 90 days. No pregnancy loss from recipient mares was recorded throughout the study. Non‐surgical embryo collection and transcervical transfer techniques can be considered useful management strategies to improve productivity from two‐year‐old donor mares.
Viability of inner cell mass versus trophectodermal cells of frozen‐thawed horse embryos
Authors: BARRY B. E. , THOMPSON D. L. , WHITE K. L. , WOOD T. C. , HEHNKE K. E. , RABB M. H. , COLBORN D. R.
Published: June 2010

Fluorescein diacetate (FDA), a fluorogenic vital stain, was used in conjunction with a silicon‐intensified target (SIT) camera and computer‐based image analysis to estimate the viability of cells of the inner cell mass (ICM) and trophectoderm (TE) of freshly collected and frozen‐thawed horse embryos. Fluorescence intensities were greater (p<0.02) for fresh ICM (0.1500) and TE (0.1686) than for frozen‐thawed ICM (0.0323) and TE (0.0694). Fluorescence intensity ratios (ICM:TE) also differed (p<0.004) between fresh (0.966) and frozen‐thawed (0.482) embryos. These results indicate that 1) the use of FDA coupled with SIT camera image analysis is a repeatable, objective method for assessing embryo viability and 2) the freeze‐thaw process is more detrimental to ICM cells than to TE cells of horse embryos.
Embryo technology applied to the conservation of equids
Authors: FARINASSO A. , DE FARIA C. , MARIANTE A. DA S. , DE BEM A. R.
Published: June 2010

With the aim of starting a programme to conserve the Wild Horse of Roraima and the Northeastern Donkey, we adapted techniques used on bovine embryos to these equids. During the breeding season of 1987/88, 120 embryo collection attempts were performed on 11 crossbred donor mares between Days 6 and 8 after ovulation. Most attempts (107) were carried out on Day 6 to give an overall recovery rate of 48.3 per cent. Of 20 Day 6 embryos that were frozen in liquid nitrogen and subsequently thawed, 17 (85 per cent) appeared viable and were transferred non‐surgically to recipient mares synchronised to within +1 to −5 days of the embryo donors. This resulted in four pregnancies at Day 60 (23.5 per cent) compared to three pregnancies resulting from the transfer of seven ‘fresh’ unfrozen embryos (43 per cent). Transfer of 10 bisected demi‐embryos to individual recipients resulted in one live foal.
Pregnancies following 24‐hour co‐culture of equine embryos on foetal bovine uterine monolayer cells
Authors: WIEMER K. E. , CASEY P. L. , MITCHELL P. S. , GODKE R. A.
Published: June 2010

A total of 77 embryo collection attempts from 28 donor mares resulted in 50 embryos (64.9 per cent recovery rate) ranging from Day‐6 morulae to Day‐7 expanded blastocysts. Thirty‐five of these embryos, classified as quality grades 1 and 2, were allotted randomly by developmental stage (Stage‐I, precapsulate and Stage‐II, postcapsulate) to a control group transferred non‐surgically within 1 h to synchronised recipients, and a treated group, cultured on a monolayer of foetal uterine fibroblast cells for 24 h prior to non‐surgical transfer to recipient mares. There was no significant difference in pregnancy rates between Stage‐I and Stage‐II embryos, nor between the control group (53.3 per cent) and the 24 h co‐cultured group (42.1 per cent). The use of a co‐culture system may provide a viable alternative to cryopreservation for the transport of equine embryos from one station to another.
A simple method for bisecting horse embryos
Authors: MÜLLER Z. , CIKRYT P.
Published: June 2010

Late morulae and blastocysts were recovered non‐surgically on Days 6 to 8 after ovulation (Day 0) from Czech warm‐blood mares which had been inseminated with fresh or frozen stallion semen. Three morulae and three early blastocysts were bisected using a microblade attached to a simple bisection tool fixed to the objective of a phase contrast microscope. The 12 resulting demi‐embryos and 13 intact (non‐bisected) blastocysts were transferred surgically via flank laparotomy to recipient mares which had ovulated +1 to −3 days with respect to the embryo donor. Pregnancy was established in nine of the 13 mares (69 per cent) which received intact embryos and in tow of the six mares (33 per cent) which received demi‐morulae. However, none of the six mares which received demi‐blastocysts became pregnant.
Micromanipulation of equine embryos to produce monozygotic twins
Authors: SKIDMORE JULIAN , BOYLE M. S. , CRAN D. , ALLEN W. R.
Published: June 2010

The uteri of Welsh Pony donor mares were flushed non surgically late on Day 5 after ovulation (at 18.00 h or midnight) or on Day 6 (between 06.00 h and 12.00 h) to recover morulae or early blastocysts. Twenty‐six embryos were recovered from 63 flushing attempts (41 per cent). To investigate the effects of in vitro culture and micromanipulation on the development of the acellular equine blastocyst capsule, intact and manipulated embryos were cultured for varying times before being fixed and stained for histological examination. The capsule developed normally on two non‐manipulated morulae and one blastocyst cultured for 12 to 48 h. However, no development or redevelopment of the capsule occurred during 48 to 96 h in culture of the 18 demi‐embryos which resulted from the bisection of two morulae and seven blastocysts. The remaining 14 embryos were also bisected and the demi‐embryos transferred surgically to synchronised recipient mares within 4 h. All eight pregnancies which developed, including two sets of monozygotic twins, originated from bisected morulae. No pregnancies developed following transfer of bisected blastocysts.
Peripheral corneal ulcers in the horse
Authors: DICE P. F. , COOLEY PENNIE L.
Published: June 2010

This report involves a retrospective study of five horses with an unusual form of progressive peripheral corneal ulcers. These ulcers were located at the perilimbal region of the cornea and spread both centripetally to mid periphery and circumferentially. Lipping of the epithelial edge was observed often. The depth ranged from superficial to mid stroma. Patients ranged from two and a half to eight years, both sexes, and were referred after a variety of antibacterial therapy. Histories were similar in that all ulcers were initially located adjacent to the limbus in one or more quadrants. No trauma was known to antedate the corneal disease and the patients were in good general health. Conjunctivectomy was performed in three patients which revealed an abundance of plasma cells and lymphocytes. All five cases were negative for a specific bacterial pathogen. Patients responded to a variety of treatment modalities: topical corticosteroid, surgical debridement, therapeutic soft contact lens (TSCL), and/or conjunctivectomy.
Aniridia in a Thoroughbred horse
Authors: UEDA Y.
Published: June 2010

Aniridia presents with very characteristic typical signs and has been reported in man (Newell and Ernest 1974), calves (Saunders and Fincher 1951) and horses (Ericksson 1955; Joyce 1983). This case report records aniridia in a Thoroughbred.

The animal, a two‐month‐old brown colt, presented with a history of unusual brightness in both eyes and strange behaviour. Clinical examination revealed curtain‐like pigmentation in the upper part of the cornea from the superior limbus which was thickened and poorly demarcated. Some vascularisation was present in the affected corneal region. The iris was absent and the tips of the ciliary body processes were apparent around the lens equator. A small central cataract was present. Intraocular pressure was normal and there were no abnormalities detected on ophthalmoscopic examination of the fundus (Fig 1). The condition was bilateral. Examinations at three and five years of age revealed no further abnormalities.

The colt was well developed from birth and although behaving as the other colts, photophobia was evident in the paddock at all times. The horse was quiet in the stable and would sometimes stare in one direction for long periods. It was nervous outside; training was carried out in the early morning as the animal exhibited certain wild behaviour in bright sunshine and reacted sharply to reflected light from pools of water. However, it was placed first on four occasions, second on five occasions and third on one occasion from 37 starts. The colt was gelded at 16 months and was the eighth foal from a mare imported from Ireland; none of the other offspring were affected and the mare showed no evidence of illness during pregnancy.
Methodology and repeatability of a standardised treadmill exercise test for clinical evaluation of fitness in horses
Authors: SEEHERMAN H. J. , MORRIS ELISABETH A.
Published: June 2010

This paper describes the methodology necessary to perform a clinical exercise test and the expected variability in an individual horse's exercise test measurements based on comparing the results of two repetitions of the test with six horses. The exercise test measurements were obtained with an open flow respiratory gas analysis system, fast time response lactate analyser and an on‐board heart rate monitor during an incremental inclined treadmill exercise test. With the exception of peak venous lactate concentration (LACpeak), the results indicate that the mean variability in peak oxygen consumption (V̇O2peak) peak carbon dioxide production (V̇CO2peak), peak respiratory exchange ratio (Rpeak), peak heart rate (HRpeak), peak packed cell volume (PCVpeak), peak total plasma protein (TPPpeak) and the maximum number of steps completed during the exercise test (STEPmax) was less than 5 per cent. Variation in the regression analysis of V̇O2, V̇CO2 and HR versus velocity was also less than 5 per cent. Slightly higher variation was recorded for LAC and R. Mean variation in the regression analysis of PCV and TPP versus velocity was more than 16 per cent. Mean variation for all of the post exercise test measurements was less than 10 per cent at 1, 5 and 15 mins post exercise. Therefore, the results obtained during a single exercise test are a reliable assessment of a horse's metabolic capability.
Investigation of the vertical hoof force distribution in the equine forelimb with an instrumented horseboot
Authors: BARREY E.
Published: June 2010

A greater knowledge of the biomechanics is necessary in equine orthopaedics, therapeutics, farriery and for the selection of athletic horses. The purpose of this study was to determine the normal distribution of the vertical component of the hoof force using a measuring boot. The measurements were carried out using 20 sound horses walking and trotting on a straight hard track. A force measuring horseshoe, attached to the foot with a boot, provided continuous recording of vertical forces at four locations on the hoof. For each measuring location, a computer program produced curves and calculated gait and force parameters. The position of the resultant force moved cranially during the stance phase. The vertical component was not distributed uniformly over the whole hoof surface. Thus the mechanical loading was greater in the caudal area than in the cranial area, especially after the foot impact on the ground. It was concluded that the heels and the quarters seemed to take a prominent part in dampening concussion and supporting bodyweight. More investigations are necessary to establish the relationships between the two functions and the frequent pathology of the caudal region of the foot.
Cardiorespiratory drift during exercise in the horse
Authors: THOMAS D. P. , FREGIN G. F.
Published: June 2010

The purpose of the present study was to measure the time‐course and degree of cardiovascular and respiratory ‘drift’ during constant submaximal exercise in the horse. One Thoroughbred and four Morgan mares were instrumented for simultaneous measurement of respiratory and blood gases which also enabled cardiac output (Q̇) to be calculated. Data were collected at rest, and at 10, 20 and 30 mins during a constant workload which elicited an initial exercising heart rate (HR) of 150 beats/min, and an approximate 15‐fold increase in oxygen consumption (VO2). Significant cardiac and respiratory drift during exercise were observed over time so that ventilation increased from 750 ± 58 to 910 ± 49 litres/min (21 per cent increase) from the 10 to 30 min time‐point (P<0.05) and HR went from 154 ± 4 to 173 ± 9 beats/min (mean ± se) over the same time period (P<0.05). Q̇ also rose from 142 ± 5 to 177 ± 17 litres/min (P<0.05) during the same interval while stroke volume (SV) was maintained. Rectal temperature (TR) and mixed venous lactate (LA) also showed significant increases during exercise while PaO2and PaCO2remained constant. The results indicate a significant degree of cardiac and respiratory drift in the horse in response to strenuous submaximal exercise. At the constant exercise work rate chosen, a levelling off, or plateauing of the selected parameters of interest was not observed. Therefore if a true exercising ‘steady‐state’ was achieved, it must have occurred very early in the exercise bout.
Alterations in plasma volume, plasma constituents, renin activity and aldosterone induced by maximal exercise in the horse
Authors: MASRI MARIA , FREESTONE J. F. , WOLFSHEIMER K. J. , SHOEMAKER K.
Published: June 2010

Plasma volume (PV) decreased by 13 per cent following the completion of 1,000 m of maximal exercise in the horse. This study demonstrated that the critical reduction in PV following maximal exercise occurred within 10 mins of completion of exercise, as previously reported in man. Total plasma protein (TPP) increased by 23 per cent at 2 and 5 mins, and by 21 per cent at 10 mins post exercise. Therefore, it does not appear to be an accurate measurement to assess the degree of PV contraction in the horse. Protein was apparently added to the intravascular space either during or following exercise. The changes in osmolality correlated strongly with those in sodium, which is the primary determinant of alterations in plasma tonicity. The increase in osmolality (12 per cent) was similar to the reduction in PV (13 per cent) concluding that a transient hypotonic fluid loss had occurred. The increase in plasma renin activity (PRA) following maximal exercise was followed by an increase in aldosterone (ALD) concentration in both magnitude and time course. Alterations in PV should be considered when interpreting electrolyte and serum enzyme activity data collected following maximal exercise.
Effect of show jumping on heart rate, blood lactate and other plasma biochemical values
Authors: ART TATIANA , AMORY HELENE , DESMECHT D. , LEKEUX P.
Published: June 2010

This study investigated some physiological responses to exercise performed by a horse during show jumping. The effects of jumping on heart rate (HR), blood lactate (LA) and some other blood values were studied in nine normal horses participating at the Belgian Junior Championship. Venous blood was sampled before and immediately after the show jumping and was analysed for packed cell volume, LA, blood glucose (GLU), total plasma protein, bicarbonate, sodium, potassium (K+), chloride, calcium and activities of plasma lactate dehydrogenase, creatine phosphokinase (CK) aspartate amino transferase and gamma glutamyl transferase (GGT). A heart rate recorder placed under the saddle allowed the continuous recording of HR from the warm‐up until 2 mins after the event. The completion of the jumping induced significant changes in all values, except in K, GLU and GGT. Resting values of LA and HR were 0.53 ± 0.05 mmol/litre and 43.9 ± 1.9 beats/min respectively. Post exercise LA reached a mean value of 9.04 ± 0.9 mmol/litre, and, during the jumping, HR rose to a peak of 191.4 ± 3.8 beats/min. The results of this study demonstrate that, although the speed and duration of such an exercise are low, show jumping represents a severe exertion which requires the use of anaerobic metabolism. This implies that the training schedule of jumpers must include power training in order to improve their anaerobic capacity.
Bicarbonate loading in the Thoroughbred: Dose, method of administration and acid‐base changes
Authors: GREENHAFF P. L. , SNOW D. H. , HARRIS R. C. , ROBERTS C. A.
Published: June 2010

Two studies were undertaken in an attempt to investigate the optimal dose, route and time course required to ‘bicarbonate load’ the Thoroughbred. During the first study a test solution of sodium bicarbonate (NaHCO3) and a control solution of water were administered via a nasogastric tube to six horses. Blood acid‐base status was determined immediately prior to and for 24 h following intubation. During the second study a standardised feed was given to four horses, with and without NaHCO3 supplementation. This was followed by a further trial involving the addition of glucose and NaHCO3 to a standardised feed. During Study 1, plasma pH peaked 8 h after NaHCO3 intubation (7.433 ± 0.020) and levels were still elevated above control values 12 h post intubation. Although there was a trend for blood PCO2 to be elevated above control values at all times after NaHCO3 administration, values were only significantly different at 4 and 5 h post intubation. The patterns of change in plasma HCO3− and blood base‐excess after NaHCO3 administration were similar. Values peaked between 3 and 6 h post intubation and were still above control values 12 h post intubation. In Study 2 attempts to alter acid‐base status by presenting NaHCO3 mixed with feed were unsuccessful because horses failed to consume the total mix, despite attempts to mask the unpalatable nature of the feed by adding glucose. The results suggest that future studies investigating the influence of NaHCO3 on exercise performance and metabolism should possibly involve administration of NaHCO3 in a greater quantity than is administered conventionally (0.3g/kg). More meaningful results may be obtained if NaHCO3 is administered as a solution, via a nasogastric tube, at least 3 h prior to exercis
Evidence for MHC class‐l restricted cytotoxicity in the one‐way, primary mixed lymphocyte reaction
Authors: O'Brien M. A. , Holmes M. A. , Lunn D. P. , Duffus W. P. H.
Published: June 2010

The one‐way primary equine mixed lymphocyte reaction (MLR) was used to generate allospecific major histocompatibilty complex (MHC) class‐I‐restricted cytotoxicity in vitro. Allospecific cytotoxicity, demonstrated against Con A stimulated peripheral blood mononuclear cells (PBMC) in a 6 h chromium‐release assay, was present from approximately 72 to 168 h of primary culture and peaked between 120 and 168 h. Optimal cytotoxicity was generated at a responder to stimulator ratio of 4:1 and at an effector to target ratio of 50:1. The cytotoxicity was blocked by an anti‐equine leucocyte antigen (ELA) class‐I and an anti‐equine CD8‐homologue monoclonal antibody. An anti‐ELA class‐11 and an anti‐equine CD4‐homologue monoclonal antibody had no significant effect.
Evaluation of some prophylactic therapies for the idiopathic headshaker syndrome
Authors: MAIR T. S. , HOWARTH S. , LANE J.G.
Published: June 2010

Eighteen horses affected by the idiopathic headshaker syndrome were studied in an owner assessed trial to test the efficacy of some prophylactic therapies. Riding the affected animal with a veil over the nostrils gave varying degrees of temporary relief in three of 10 horses. Local (intra‐nasal) corticosteroid therapy was reported to be slightly effective in three of nine horses, but treatment with sodium cromoglycate, systemic corticosteroid, flunixin meglumine and an antihistamine were generally ineffective. Bilateral infraorbital neurectomy provided sustained relief in three of seven horses, but in one of these cases, a reaction at the neurectomy site necessitated another surgical procedure after six months. A fourth horse was reported to be slightly improved after neurectomy. A period of nasal irritation resulting in selfinflicted trauma was a common complication of this surgery.
A comparison of injectable anaesthetic regimens in Mammoth asses
Authors: MATTHEWS NORA S. , TAYLOR T. S. , HARTSFIELD S. M. , WILLIAMS J. D.
Published: June 2010

Xylazine (1.1 mg/kg body weight [bwt])‐ketamine (2.2 mg/kg bwt) (X/K) anaesthesia was evaluated, in nine Mammoth asses, for effectiveness and compared with two other injectable anaesthetic combinations: xylazine (1.1 mg/kg bwt) ‐ butorphanol (0.044 mg/kg bwt)‐ketamine (2.2 mg/kg bwt) (X/B/K); and xylazine (1.1 mg/kg bwt)‐tiletamine‐zolazepam (1.1 mg/kg bwt) (X/T). All drugs were given intravenously (iv). Heart rate, respiratory rate, systolic blood pressure, arterial blood pH, PCO2, PO2, recumbency time and number of attempts to stand were measured. Quality of induction and recovery, muscle relaxation and response to stimulus were evaluated subjectively. One animal did not become recumbent with X/K. Recumbency times were significantly (P < 0.05) different: the shortest time was with X/K (24 mins) and the longest time with X/T (46 mins), with X/B/K, it was 37 mins. Asses required significantly more attempts to stand with X/T (n=3) than with X/K (n/1) or X/B/K (n=2). No significant differences in heart rate, respiratory rate, blood pressure, arterial PO2or PCO2were detected between groups. Arterial pH was significantly lower at 15 mins in the X/B/K and X/T groups than in the X/K group. Although X/K generally produced effective immobilisation, the combinations of X/B/K and X/T appeared to be more satisfactory and relatively safe, and provided longer recumbency times and increased muscle relaxation compared with X/K.
Review Article: Blood platelets and their role in the genesis and sequelae of intestinal ischaemia
Authors: Evans R. J.
Published: June 2010

Activation of platelets is the key step in the formation of macroscopic thrombi and emboli and in micro‐thromboembolism associated with disseminated intravascular coagulation (DIC). Macroscopic thrombosis may compromise the blood supply of the gut. Strangulation or infarction of the gut, from whatever cause, commonly result in endotoxaemia, DIC and multiple organ failure. Equine platelets may be activated physiologically by a wide range of agonists. Information is now emerging about the receptor populations and intracellular signalling pathways of equine platelets. Less is known about platelet‐vessel wall interactions in the horse or the mechanisms of platelet activation in endotoxaemia. Antiplatelet drugs have been disappointing in endotoxaemia, possibly because of the relative unimportance of thromboxane production in the activation of equine platelets. Dextran 70, however, is a useful treatment of thromboembolic colic and the mechanism of action is now beginning to be understood.
Serosal adhesions ‐ the next hurdle in colic surgery
Authors: Baxter G.
Published: June 2010

“The story for all these substances has been very much the same: initial enthusiasm, often actual use in clinical cases, then further investigations which showed either no effect at all or an actual increase in adhesion formation compared to controls, then finally the abandonment of that particular material.”
Gastric secretion in foals: measurement by nasogastric intubation with constant infusion and aspiration
Authors: Andrews F. M. , Jenkins Christine C. , Frazier Donita , Blackford J. T.
Published: June 2010

A technique comprising constant infusion and aspiration via nasogastric tube was used to quantify basal gastric secretion in 9 healthy foals aged 4–7 months and weighing 156 to 215 kg. Gastric fluid was collected continuously for 3 h from anin situdouble lumen nasogastric tube attached to a constant suction device (5–10 mmHg). Phenol red (50 mg/litre), an inert marker, was infused continuously (250 ml/h) during the same period to determine loss of gastric fluid through the pylorus. Samples were collected every 15 mins and aspirated volume (VASP), pH, phenol red recovery (PRR) and hydrogen ion concentration (AO) were measured. Gastric secretory volume (VS) and acid concentration (ACD) were calculated. The mean (sd) VASPwas 6.54 (1.31) ml/kg bodyweight (bwt)/h; pH was 1.76 (0.25), PRR was 77.7% (11.7), and AO was 0.43 (0.18) mmol/kg bwt/h. Mean (sd) ACD and VSwere 59.17 (18.88) mmol/litre and 7.07 (1.73) ml/kg bwt/h, respectively. The AO, ACD, and VSwere corrected for PRR. This technique is an alternative to invasive procedures and may be useful for evaluating basal and stimulated gastric secretion in foals and horses.
Pharmacokinetics and antisecretory effects of intravenous omeprazole in horses
Authors: Jenkins Christine C. , Frazier Donita L. , Blackford J. T. , Andrews F. M. , Mattsson H. , Olovsson S‐G. , McCleod Margaret
Published: June 2010

Eight young female horses with chronic gastric cannulae received 0.5 mg omeprazole/kg bwt iv once daily for 5 consecutive days. Gastric secretion was measured on the 1st and 5th day. Basal secretion was determined 1 h before and 1 h after the omeprazole dose, followed by pentagastrin stimulation for 2 h. Gastric juice samples were collected from the cannula every 15 mins for the determination of volume, pH, acidity, and acid outputs. As control, sterile water was similarly administered to all 8 horses. Pharmacokinetic evaluation of intravenous omeprazole was determined concurrently on the 1st and 5th day of administration.

Omeprazole reduced both basal and stimulated acid output (mmol H+/h) by more than 90%, with a significant increase in gastric juice pH both on the 1st and 5th day of administration. A trend suggesting a long duration of inhibitory action was observed 23 h after the 4th dose of omeprazole since 58% of gastric acid output was inhibited. Thus omeprazole shows potential as a once a day antisecretory drug in horses.

Plasma omeprazole concentration versus time profiles were best described using a two‐compartment model. There was no statistical difference between the pharmacokinetic disposition of omeprazole on Days 1 and 5. The elimination half‐life of intravenous omeprazole was about 30 mins.
Pathophysiology, cellular and molecular mechanisms of foetal growth retardation
Authors: HAN V. K. M.
Published: June 2010

In mammals, size at birth is the outcome of length of gestation and rate of foetal growth. In the absence of premature delivery, foetal size within species is determined principally by foetal growth rate which is dependent on both genetic and epigenetic factors. Failure of either of these mechanisms leads to foetal growth retardation. In mammals, including human infants, foetal growth retardation can occur naturally or pathologically. One major cause for natural foetal growth retardation or runting is the increase in litter size. In many cases, however, the cause of runting is unknown. Parental genotype or antigenic differences between the mother and the developing conceptus may be potential causes. Pathological foetal growth retardation or intrauterine growth retardation (IUGR) is due to genetic causes (chromosomal abnormalities or inherited syndromes) or epigenetic causes (intrauterine infections, toxins and chemicals, maternal diseases of pregnancy affecting the placenta). The underlying pathophysiological processes that occur at the cellular and molecular level in IUGR are still unknown. Reduction in the supply of substrates that are necessary for normal cellular function, and alteration in mediator molecules that regulate cellular growth and differentiation, are important mechanisms. A decrease in growth promoting factors or an increase in growth inhibitory factors may lead to growth failure. Growth factors and their receptors are expressed in the developing embryo (as early as the 1–2‐cell stage), placenta and maternal uterine tissues, suggesting that these molecules may play a role in regulating normal growth and differentiation of the conceptus as well as maternal reproductive tissues. The local expression within developing tissues indicates that these factors act in either autocrine or paracrine mechanism. Recent studies using gene targeting to knock out one allele of insulin‐like growth factor II (IGF II) gene in mice which resulted in growth retarded pups at birth, strongly support the importance of local IGF II in regulating tissue growth. Foetal growth retardation has also been induced experimentally in several species using one of the following methods: (i) maternal undernutrition, (ii) chronic hypoxia, (iii) prolonged reduction in uterine blood flow, (iv) reduction in placental size, and (v) endocrine alterations. These models provide useful information on the physiological mechanisms underlying a specific type of growth retardation. These in‐vivo models and in‐vivo tissue culture models can now be analysed by biochemical and molecular biological techniques to unravel the basic mechanisms that underlie foetal growth retardation.
Some aspects of perinatal maturation and adaptation
Authors: MELLOR D. J.
Published: June 2010

Physiological challenges facing the perinatal individual are huge. This is partly because of the marked and abrupt change from the intrauterine to the extrauterine environment, but also because the physiological responses to that change depend upon systems whose maturation is affected markedly by birth. Perinatal maturation appears, therefore, both to precede and accompany the physiological adaptations required for neonatal survival. This review does not provide a comprehensive coverage of perinatal physiology but directs attention towards evaluating constraints on foetal and neonatal thermogenesis, especially those imposed by postnatal availability of metabolic fuels in body reserves deposited before birth and acquired in colostrum and milk after birth. The relative importance of the supply of carbohydrate from body reserves and colostrum is examined. Carbohydrate is the major rate‐limiting substrate with respect to heat production. It is shown that in the normal birth environments of several species, including the horse, colostral supply of lactose is not adequate to meet the entire carbohydrate needs of the neonate. It must, therefore, draw on its body glycogen reserves to sustain the required rates of heat production during the first day after birth. Gastrointestinal maturation and growth play a major part in the initial and continued provision of substrates for general metabolism and growth. Pre‐natal and post‐natal development of the stomach and intestines in a number of species are considered, including their disproportionately large growth compared with the body as a whole during the first 1–3 days after birth. Possible contributions to gastro intestinal growth and body growth of milk‐borne growth factors such as epidermal growth factors and the insulin‐like growth factors are considered. The role, as a possible significant stimulus to gastrointestinal growth and maturation immediately after birth, of the high levels of these growth factors in colostrum is evaluated.
Use of sperm binding to homologous hemizona pellucida to predict stallion fertility
Authors: FAZELI A. R. , STEENWEG W. , BEVERS M. M. , BRACHER V. , PARLEVLIET J. , COLENBRANDER B.
Published: June 2010

Equine oocytes were obtainedpost mortemfrom slaughterhouse ovaries and by transvaginal ultrasound‐guided follicle aspiration. The oocytes were denuded and stored in salt solution at 4°C. On the day of the experiment the oocytes were bisected by micromanipulation surgery, thus providing two equal matching hemizonae from each oocyte. Three pairs of stallions were formed, each consisting of a fertile and subfertile Dutch Warmblood stallion. Matching hemizonae from 5 oocytes were used for each pair of fertile and subfertile stallions and the number of spermatozoa bound to the outer‐side of each hemizona during incubationin vitrowas assessed. The numbers of bound spermatozoa from fertile stallions were significantly higher than those from subfertile stallions (P<0.05). The results of this investigation encourage further use of the hemizona assay for evaluation of stallion fertility.
Atlas of chromatin configurations of germinal vesicle‐stage and maturing horse oocytes
Authors: HINRICHS K. , SCHMIDT A. L. , SELGRATH J. P.
Published: June 2010

The fluorescent, DNA‐specific label, Hoechst 33258, was used to determine the chromatin configuration of immature and maturing horse oocytes. The stain was simple to use and effective in revealing the chromatin of horse oocytes without need for clearing of lipid. The chromatin configuration of oocytes known to have a germinal vesicle fell into two major categories: fluorescent nucleus, in which the entire nucleus fluoresced with or without clumps of chromatin within; and compact chromatin, in which only one compact mass of chromatin was visible. These classifications were further broken up into diffuse, spotty or crinkled fluorescing nucleus, and compact, faded or loosely compact condensed chromatin. The physiological relevance of the different chromatin configurations of germinal vesicle stage oocytes is presently unknown. The chromatin configurations of maturing oocytes were similar to those seen in other species.
Repeated transvaginal ultrasound‐guided follicle aspiration in the mare
Authors: BRACHER VERENA , PARLEVLIET JOYCE , FAZELI A. R. , PIETERSE M. C. , VOS P. L. A. M. , DIELEMAN S. J. , TAVERNE M. A. M. , COLENBRANDER B.
Published: June 2010

Transvaginal ultrasound‐guided follicle aspiration was performed repeatedly in 5 Dutch Warmblood mares during a time span of 3 months (mid‐June‐mid‐September 1992). During 24 aspiration sessions (4–7/mare), 200 follicles were aspirated and 34 oocytes retrieved, giving oocyte recovery rates of 12.3% and 24.4% when using single channel needles or double barrel needles respectively. There was no significant effect of cycle stage on oocyte recovery rates. Follicle aspiration performed without any hormonal pretreatment gave significantly higher oocyte recovery rates of 26.9%, compared with 8.2 and 15.3% for pretreatments with prostaglandin F2α and human chorionic gonadotrophin respectively. Measurements of daily plasma progesterone concentrations in the mares revealed that follicle aspiration induced luteinisation of the follicles within 1–6 days after aspiration, resulting in a progesterone pattern similar to that of a normal oestrous cycle with ovulation when follicles were aspirated during oestrus, or in prolonged dioestrus in the mares in which follicle aspiration was performed during the luteal phase. The procedure was well tolerated by the animals and no clinical side effects were noted. This technique provides a non‐invasive, relatively simple method for the repeated puncture of multiple immature and preovulatory follicles in the mare and the possibility of obtaining up to 6 oocytes per mare in a single follicle aspiration session.
The hatching process of equine embryos in vitro
Authors: HOCHI S. , BRAUN J. , OGURI N.
Published: June 2010

Blastocysts (5 unexpanded, 5 expanding, 2 hatched) were recovered non‐surgically between 144 and 192 h after detection of ovulation. Unexpanded and expanding embryos were cultured (TCM199 + 10% foetal bovine serum) for 10 days. Mean diameter was 168.0 μm for unexpanded and 251.0 μm for expanding blastocysts, respectively. Unexpanded embryos started to hatch from the zona pellucida (ZP) when their diameter reached 405.4 μm (embryonic age 240.0 h). Four embryos squeezed through a small opening in the ZP whereas 1 embryo gradually tore open the ZP. Three embryos completed the hatching process within 96–120 h. In contrast, expanding embryos started to hatch at a mean diameter of 499.8 μm (embryonic age 192.0 h). Four embryos escaped from the ZP within 12 h. One embryo squeezed through the ZP but did not shed the ZP entirely during culture. In‐vitro hatched embryos continued to expand spherically until reaching a maximum mean diameter of 1141.7 μm (unexpanded embryos) and 2765.0 μm (expanding embryos), except for 1 embryo which attached to the bottom of the culture dish. In completely hatched embryos, no capsule could be detected at x200 magnification after staining. Three embryos which did not entirely hatch from the ZP until the end of culture had a capsule remaining inside the ZP. In 1 case, a thin acellular layer was detected in the shed ZP after 0.3% trypsin treatment. Both freshly recovered hatched blastocysts (diameter 640 μm, 697 μm) had a clearly visible capsule around the trophectoderm cells. Equine blastocysts not only lost their zona pellucida but also their capsule during the hatching process in vitro.
Purified pig FSH increases the rate of double ovulation in mares
Authors: FORTUNE JOANNE E. , KIMMICH T. L.
Published: June 2010

A commercial preparation of porcine FSH (Folltropin) was used to determine whether injections of FSH early in the oestrous cycle, before a large dominant follicle is present, can stimulate multiple ovulations in cycling mares. In the 1990 and 1991 breeding seasons, after injection of 8, 16 or 32 mg FSH twice daily beginning on Day 6 and PGF2α on Days 5 and 6, the rate of multiple ovulation was increased significantly to 1.83, 1.54, and 1.50, respectively, compared with 1.19 for saline‐injected controls. All multiple ovulations were double ovulations. In 1992, mares were injected with 8 mg FSH twice daily beginning on Day 3, with injection of PGF2α once daily on Days 3–6 (‘early’ group) and the response compared with that of the same mares to the protocol used in 1990‐91 (‘late’ group). PGF2α injection caused a rapid decline in plasma progesterone in both groups. FSH did not increase ovulation rate in either group but the rate of double ovulations was increased in the ‘early’ group, for saline‐ and FSH‐treated mares, in comparison with untreated control cycles for the same mares.

Ultrasonographic analysis of growth and regression of individual follicles ≥15 mm and ≥25 mm in mares treated during the 1990‐92 breeding seasons revealed no consistent effect of FSH treatment on those follicular populations. These results suggest that treatment with high doses of a commercial preparation of porcine FSH can produce a modest increase in ovulation rate. Although the increase in ovulation rate was small, the response was consistent; no mare ovulated more than 2 follicles and double ovulations were synchronous, occurring on the same or succeeding days in almost all mares.
Effect on ovulation rate of passive immunisation of mares against inhibin
Authors: McCUE P. M. , HUGHES J. P. , LASLEY B. L.
Published: June 2010

Fifteen light‐horse mares were monitored daily by palpation and ultrasonography for one oestrous cycle and then randomly divided into two treatment groups. Five mares were treated with 2 litres of normal ovariectomised mare plasma (OVX) on Day 10 after ovulation and 10 mares received 2 litres anti‐inhibin plasma (a‐INH) beginning on Day 10 after ovulation. Mares receiving OVX plasma all had single ovulations after treatment, while 5 of the 10 mares receiving a‐INH plasma had multiple ovulations (mean 1.6 ± 0.2, range 1–3). No significant effect of a‐INH plasma treatment was detected in plasma concentrations of FSH, oestradiol or progesterone. These results demonstrate that passive immunisation of mares with a‐INH plasma can induce multiple ovulations, and thus eliminate the need for daily gonadotrophin treatment or a prolonged series of active inoculations against inhibin.
Habituation of horses to treadmill locomotion
Authors: BUCHNER H. H. F. , SAVELBERG H. H. C. M. , SCHAMHARDT H. C. , MERKENS H. W. , BARNEVELD A.
Published: June 2010

Habituation to treadmill locomotion was investigated in ten Dutch Warmblood horses during a one‐week training programme. Kinematics of the horses were recorded using a CODA‐3 system and unidirectional accelerometers attached to all hooves. Horses were exercised for five days, twice a day at the walk and trot for five minutes at both gaits. Temporal and spatial stride variables and vertical trunk movement were analysed.

The results indicate differences in habituation between different variables and gaits. At the walk, changes in stride duration and limb movement angle were found up to the last measurement. At the trot, all variables including constancy of stride approached constant values by the third session. At the beginning of each training session rapid adaptation occurred, disregarding the first minute of a session for locomotion studies. In conclusion, locomotion analysis at the trot requires training for a minimum of two sessions. For measurements at the walk, longer periods are recommended.
Treadmill training induced changes to some kinematic variables measured at the canter in Thoroughbred fillies
Authors: CORLEY J. M. , GOODSHIP A. E.
Published: June 2010

Six Thoroughbred fillies undertook a high intensity treadmill exercise programme over an 8 week period. Kinematic parameters of the left front limb were measured using the MacReflex system as the horses were cantered on a left lead. Measurements were made as the horses performed a standardised stepwise exercise test on the treadmill (speeds 7‐11m/s, 0% slope.) The aim was to study objectively the effects of training on the equine locomotor apparatus and to test the hypothesis that horses would display mechanical adaptation to aspects of their gait, as a result of treadmill training. The variables measured were stride length; stride frequency; stance time, as a percentage of stride time; relative movements of limb joints in the X (horizontal) and Y (vertical) directions; angles about the carpus and fetlock joints; and total ranges of motion of the carpus and fetlock joint. Statistical significance was chosen at the level p<0.05. Training induced significant changes to several aspects of the stride cycle. Percentage stance times were reduced across all speeds and significant changes were observed in the movements of the limb joints resulting in increased vertical hoof lift. Significant increases were also seen in the carpal and fetlock joint ranges of motion and also in carpal joint angles. The results suggest that the training regime employed produced significant alteration in stride kinematics at the canter.