Experimental Mares Research Articles

APPLICATION OF OVASCAN AND PROGESTERONE CONCENTRATION FOR PREDICTION OF OVULATION DURING ESTRUS IN THE MARE

The estrous cycle of 8 Arabian mares was followed for one year, by visual observation of the estrous behaviour and by teasing with a stallion. Serum progesterone concentration was determined by RIA, Vaginal electric resistence was studied with aid of Ovascan, comapared with the changes in the reproductive tract as determined by rectal examination for prediction of ovulation. The changes in the reproductive tract and the behavioural manifestations expressed during the cycle indicated that the experimental mares were exhibiting estrous year arround, however, 75% of the cycles were observed during the months from March to August and 25% during the. rest of the year. The total number of cycles exhibited by the mares averaged 68 cycles, of these 22 cycles were observed during Summer, 20 during Spring, decreased to 13 cycles during Fall and 13 during Winter. the length of the estrous cycle ranged between 24-26. 31 days, the average estrus length ranged between 5.5-8.6 days andthe luteal phase ranged from 19.04-24.87 days. The ovascan readings showed decline by 50 degrees, constantly, a day preceeding ovulation, compared to the readings during the rest of estrus days and this finding was confirmed by rectal palpation of the reproductive tract in succeeding day which disclosed the disappearance of the mature follicle and the: presence of the ovulation site on the ovary, consequently, the estrous signs faded away gradually within 24-48 hours of the ovuletion. Serum progesterone concentration, during’ the estrus and one day before ovulation ranged between 0.58 -1.05 ng/ml, while mean luteal phase concentration was 10.2820.89 ng/ml. The results of the present study disclosed that the mares in Iraq could be bred any time of the year and it is most probable that measurement of progesterone concentration will have more practical application for monitring ovarian activity and estrus prediction, if. a rapid system of measurment made avilable (as progesterone strip). The application of Ovascan proved effecient tool for prediction of ovulation in the mare, providing information for synchroniztion of service with ovulation, a mean augmenting fertility and avoiding rectal palpation which hinder service.

Automatic early detection of induced colic in horses using accelerometer devices.

To seek appropriate veterinary attention for horses with colic, owners must recognise early signs. Direct observation of horse behaviour has several drawbacks: it is time-consuming, hard to see subtle and common behavioural signs, and is based on intuition and subjective decisions. Due to recent advances in wearables and artificial intelligence, it may be possible to develop diagnostic software that can automatically detect colic signs. To develop a software algorithm to aid in the detection of colic signs and levels of pain. In vivo experiments. Transient colic was induced in eight experimental mares with luteolytic doses of prostaglandin. Veterinarians observed the horses before and throughout the interventions and assigned pain scores which were used to separate colic episodes into none (pain score ≤5), level 1 (pain score 6-10) or level 2 (pain score ≥11). Accelerometric data and videos were collected throughout the experiments and using accelerometric data, the horse's behaviour was classified into normal and 10 pain-related behaviours and an activity index was calculated. Models were designed that utilised behaviour and activity index characteristics both detecting the presence of colic and assessing its severity. To determine the accuracy of the model, the ground truth, that is the veterinarians' observation of colic signs and assessment of pain level, was compared with the automatic detection system. The cross-validation analysis demonstrated an accuracy of 91.2% for detecting colic and an accuracy of 93.8% in differentiating between level 1 colic and level 2 colic. The model was able to accurately classify 10 pain-related behaviours and distinguish them from normal behaviour with a high accuracy. We included a limited number of horses with severe pain related behaviours in the dataset. This constraint affects the accuracy of categorising colic severity rather than limiting the algorithms' capacity to identify early colic signs. Our system for early detection of colic in horses is unique and innovative, and it can distinguish between colic of varying severity.

Increasing the milk productivity of Kazakh jabe horses.

The purpose of the study was to determine the milk productivity and chemical composition of the milk of mares of the Kazakh breed of the jabe type (KJ) and the Novoaltay-Kazakh crossbreeds of the 1st generation (NA x KJ) in the conditions of herd keeping. To determine the milk productivity of mares, 2 experimental groups were formed with a total of 30 mares, 15 individuals were selected in each group. The studied animals were formed according to the principle of pairs of analogues in the context of full-age groups from 5 to 11 years. Kazakh horses of the jabe type in the group of experimental mares in milk have an average live weight of 433.5 kg, and are significantly inferior to the Novoaltay-Kazakh crosses (515.3 kg). The body measurements were 142.0-149.0-174.9-18.2 cm in Kazakh horses of the jabe type, and 150.1-157.1-186.7-20.02 cm, respectively, in Novoaltay-Kazakh crossbreeds. According to the results of studies, the milkiness of mares of the Novoaltay-Kazakh crosses for 105 days of lactation averaged 1932 liters or higher by 25.2% (487.2 liters) than the milkiness of mares of the Kazakh breed of the jabe type. As a result of studies on the composition of milk of mares of different genotypes, it was found that in mares of Kazakh jabe, on average, protein and fat indicators compared to Novoaltay-Kazakh crossbreeds were higher by 0.07% and 0.05%. In the course of determining the live weight of mares among the experimental groups, it was found that the Novoaltay-Kazakh crossbreeds, on average, had a higher live weight of 515.3 kg or higher compared to the Kazakh jabe by 81.8 kg (15.8%). Thus, the studies have proved the prospects of using stallions of the Novoaltay breed to increase the milkiness of local Kazakh horses of the jabe type in herd and pasture conditions.

A Wide Range of Endocrine and Hematochemical Changes in the Reproductive Process of Early Pregnant Mares

The aim was to compare temporarily together the changes occurred along the early pregnant and nonpregnant mares on the ovarian, adrenocortical, thyroid, and hematochemical profiles (total protein, glucose, albumin, complete blood count). Sixteen mares were randomly divided into two groups: the experimental group of 10 mares submitted to artificial insemination, and the control group of six mares no submitted to insemination. The experimental group was analyzed after the human chorionic gonadotropin treatment (baseline = day 0), after the artificial insemination (T1), 24 hours after (T2), 15 days after (T3), and 30 days after (T4) the insemination; the control group was analyzed after placebo treatment (day 0), considering T1 the day after the placebo treatment and T2-T4 the time points after. An interaction between treatments and sampling time on estrogen (E2) (P < .0001) and progesterone (P4) (P < .0001) was observed. Compared with control group, at T4, experimental group showed higher E2 (P < .001), whereas P4 were lower (P < .001). A significant effect of experimental treatment over time for cortisol (P = .005) and glucose (P = .054), with the highest cortisol and glucose in the experimental mares, was observed. A significant effect of time for cortisol (P < .001), total protein (P < .01), glucose (P = .054), and white blood cell (P < .01) was observed in the experimental group. The trend of cortisol and glucose may probably reflect the shift of energy metabolism in anabolic and/or catabolic directions along the onset of pregnancy.

Effects of dexamethasone treatment on insulin sensitivity, insulin, thyroxine, and triiodothyronine concentrations, and the MSH and ACTH responses to sulpiride in geldings

Two studies were conducted to determine efficacy of cabergoline for suppressing prolactin (PRL) and the possible effects on vernal transition in mares. In experiment 1, six mares each received either vehicle or cabergoline (5 mg, intramuscularly) every 10 days for 12 treatments beginning February 4, 2013. Blood samples were drawn regularly, and mares were challenged with sulpiride periodically to assess PRL suppression. Weekly hair samples were obtained to determine shedding. Prolactin was suppressed (P < .05) by cabergoline, but suppression waned in spring. There was no effect (P > .05) of treatment on day of first ovulation, luteinizing hormone, or follicle stimulating hormone. Hair shedding was generally suppressed (P = .05). In 2014 (experiment 2), eight of the same 12 mares were used in a similar experiment to determine if the rise in PRL observed in experiment 1 was due to refractoriness to cabergoline or perhaps another factor. Treatment began on April 6, 2014, corresponding to the increase in PRL in treated mares in experiment 1. Mares were treated with cabergoline or vehicle until June 5. Prolactin was suppressed (P < .05) by cabergoline, and the pattern of apparent escape from suppression was similar to year 1. We conclude that (1) cabergoline at this dose alters hair shedding but does not alter the time of first ovulation in mares and (2) relative to our previous reports of cabergoline treatment in the fall, there is a seasonal effect on the ability of this dose of cabergoline to suppress unstimulated PRL secretion.

Effect of Repeated Cabergoline Treatment on the Vernal Transition and Hair Shedding of Mares (Year 1) and a Subsequent Comparison of the Effect of Starting Date on Prolactin Suppression (Year 2)

Two studies were conducted to determine efficacy of cabergoline for suppressing prolactin (PRL) and the possible effects on vernal transition in mares. In experiment 1, six mares each received either vehicle or cabergoline (5 mg, intramuscularly) every 10 days for 12 treatments beginning February 4, 2013. Blood samples were drawn regularly, and mares were challenged with sulpiride periodically to assess PRL suppression. Weekly hair samples were obtained to determine shedding. Prolactin was suppressed (P < .05) by cabergoline, but suppression waned in spring. There was no effect (P > .05) of treatment on day of first ovulation, luteinizing hormone, or follicle stimulating hormone. Hair shedding was generally suppressed (P = .05). In 2014 (experiment 2), eight of the same 12 mares were used in a similar experiment to determine if the rise in PRL observed in experiment 1 was due to refractoriness to cabergoline or perhaps another factor. Treatment began on April 6, 2014, corresponding to the increase in PRL in treated mares in experiment 1. Mares were treated with cabergoline or vehicle until June 5. Prolactin was suppressed (P < .05) by cabergoline, and the pattern of apparent escape from suppression was similar to year 1. We conclude that (1) cabergoline at this dose alters hair shedding but does not alter the time of first ovulation in mares and (2) relative to our previous reports of cabergoline treatment in the fall, there is a seasonal effect on the ability of this dose of cabergoline to suppress unstimulated PRL secretion.

249 AN EFFICIENT AND REPEATABLE IN VITRO FERTILIZATION TECHNIQUE IN THE EQUINE FOR PRESERVATION OF ENDANGERED SPECIES

Most wild equids are currently endangered or threatened, as mentioned in the International Union for the Conservation of Nature Red List, and several domestic horse breeds are at risk of extinction. Genome resource banking requires cryoconservation of semen, oocytes, and/or embryos. Embryo production in equids is limited in vivo because routine induction of multiple ovulation is still ineffective. Embryo production in vitro allows the production of several embryos per cycle that could easily be frozen because of their small size. Intracytoplasmic sperm injection has been widely adopted to generate horse embryos in vitro; however, intracytoplasmic sperm injection is time-consuming and requires expensive equipment and expertise in micromanipulation. Several attempts to establish an efficient IVF technique in the equine were performed, but reported IVF rates remain quite low and no repeatable equine IVF technique was available. Our objective was to develop an efficient and repeatable IVF technique in the equine. Immature cumulus-oocyte complexes (COC) were collected either from slaughtered mares in a local slaughterhouse or from our experimental mares by ovum pick up (OPU). The COC were cultured for 26 h in an in vitro maturation (IVM) medium or in preovulatory follicular fluid (FF) collected by OPU, pre-incubated for 30 min in oviducal fluid collected from slaughtered females, co-incubated for 18 h with fresh spermatozoa treated with procain, and cultured in SOF for 30 h. They were fixed and analysed either after 18 h IVF (experiment 1) or after 30 h in vitro development (experiment 2). In experiment 1, COC were collected from slaughtered mares and analysed after 18 h IVF. Zygotes with 2 pronuclei were observed. The IVF rate was similar for oocytes matured in IVM medium (22/33, 67%) or FF (24/42, 57%; chi-square test, P &gt; 0.05). In experiment 2, COC were collected from slaughtered mares and from experimental mares and analysed after 30 h of in vitro development. We observed zygotes with 2 highly decondensed pronuclei, pronuclei decondensation being the first step of embryo development. For oocytes collected from slaughtered mares, the percentage of zygotes was similar for oocytes matured in IVM medium (8/11, 73%) or FF (10/15, 67%). For oocytes collected by ovum pickup, the percentage was similar for IVM medium (3/5, 60%) or FF (6/8, 75%). We also observed some embryonic structures with several nuclei, but the quality of these embryos was poor. In conclusion, we have established an efficient IVM-IVF technique that allows the first step of embryo development. Because we obtained similar results for 4 years, we consider that this efficient technique is repeatable. Further experiments are in progress to improve the quality of the embryos.

Processionary Caterpillar Setae and Equine Fetal Loss

Six pregnant Standardbred mares aged between 6 and 14 years were gavaged with 50 g or 100 g of suspended emulsified whole Processionary caterpillars (Ochrogaster lunifer) for 5 days during 2 experiments undertaken to study the etiology of equine amnionitis and fetal loss (EAFL). The 6 treated mares and 1 untreated mare were between 128 and 252 days gestation. Mare 1 (untreated) was euthanized on day 5 of the treatment period, while the treated mares were euthanized on days 2, 4, 8, 10, 12, and 24 days from their first treatment. Caterpillar setae were not found in the untreated mare. Setal fragments were present in all regions of the gastrointestinal tracts in all treated mares, the uteri and mesenteric lymph nodes of 5 mares, and the liver of 4 mares. Acute gastroenteritis of varying severity was present in all treated mares, and 5 of 6 mares had acute colitis and endometritis. Focal hyperplastic serositis was found in the duodenum, cecum, dorsal colon, and uteri of various mares occasionally with embedded setal fragments. Setal invasion of the mucosa evoked a range of lesions including superficial erosion to deep ulceration. Inflammation in deeper tissues ranged from unapparent to neutrophilic (microabscesses), eosinophilic, or mononuclear (microgranulomas). The finding of setal fragments within the uterus of experimental mares suggests that direct migration of setal fragments acting as a bacterial vector is a likely mechanism for the bacterial abortions that characterize equine amnionitis and fetal loss.

Effects of a commercial canine gonadotropin releasing hormone vaccine on estrus suppression and estrous behavior in mares

We investigated the effect of immunization against gonadotropin releasing hormone (GnRH) using a commercial canine GnRH vaccine on estrus suppression and unwanted estrous behavior in mares. In experiment 1, mares were immunized (n=6) twice with vaccine (5mL) given intramuscularly 4 weeks apart or received a control diluent (n=5). Transrectal ultrasonographic examination of the reproductive tracts was performed three days a week for 40 weeks after initial vaccination. Blood samples were collected weekly for GnRH antibody titer and progesterone concentration determination. In experiment 2, privately-owned mares (n=12) were immunized twice with vaccine (1mL) given intramuscularly 4 weeks apart. Blood samples were collected prior to each vaccination as well as 12 and 20 weeks after initial treatment, and transrectal ultrasonographic examinations of the reproductive tracts were performed 12 weeks after the first vaccination. Vaccinated mares in experiment 1 responded with a GnRH antibody titer, progesterone concentrations significantly lower than controls, and cessation of ovarian activity. Vaccinated mares in experiment 2 also responded with a GnRH antibody titer, progesterone concentrations that remained basal for the duration of the study, and cessation of ovarian activity. Owners of vaccinated mares in experiment 2 reported that the number of unwanted estrous behaviors present before vaccination significantly decreased following vaccination. In conclusion, GnRH immunization using a canine GnRH vaccine is an effective method for suppressing estrus and unwanted estrous behavior.

Relationship between infection, inflammation and premature parturition in mares with experimentally induced placentitis

Ascending placentitis results in premature birth and high foal mortality. By understanding how placentitis induces premature delivery, it may be possible to develop diagnostic markers and to delay premature delivery pharmacologically, thereby decreasing perinatal foal mortality. To identify relationships between bacterial infection, inflammation and premature parturition in mares with experimentally induced placentitis. Experiment 1: Concentrations of allantoic fluid prostaglandins (PGs) F2alpha and E2 were measured in 8 mares after intracervical inoculation with Streptococcus equi ssp. zooepidemicus (at Days 285-291 of gestation) until parturition and compared with controls (n = 4). Experiment 2: mRNA expression of interleukin (IL)-1beta, IL-6, tumour necrosis factor (TNF)-alpha and IL-8 in the chorioallantois from inoculated mares in Experiment 1 were compared with 7 mares that foaled normally. Bacterial inoculation resulted in 7 aborted fetuses and birth of one premature, viable foal. Infection was associated with inflammation of the chorioallantois in the region of the cervical star, isolation of bacteria and high concentrations of PGE2 and PGF2alpha in allantoic fluid obtained within 48 h of delivery (P = 0.04). Chorioallantois from all mares expressed mRNA for IL-8, TNF-alpha, IL-6 and IL-1beta. Experimentally infected mares expressed more mRNA for IL-6 (P = 0.003) and IL-8 (P = 0.009) in the cervical star region and more mRNA for IL-6 (P = 0.004) in tissues from placental horns than control mares. Bacterial placentitis may result in liberation of cytokines from the chorioallantois and prostaglandin formation leading to abortion or birth of a precociously mature foal.

Stimulation of prolactin after estradiol pretreatment: Comparison of polymer formulations for domperidone and sulpiride and oral administration of sulpiride in horses

Stimulation of prolactin after estradiol pretreatment: Comparison of polymer formulations for domperidone and sulpiride and oral administration of sulpiride in horses

Foraging opportunity: a crucial criterion for horse welfare?

This study aimed at determining the effect of the increase of foraging opportunities on the behaviour and welfare of breeding mares housed in individual boxes but allowed outside 6 h a day in a bare paddock. One hundred Arab breeding mares were divided into two groups of 50 according to the treatment and allowed outside in two bare paddocks at the same density (115 mare/ha) where water and shelter were provided. The treatment consisted in providing the opportunity to forage on hay. Twenty-minute animal focal samplings and scan samplings were used to determine the time budget of the mares during the period from 0900 to 1500 h and study their social behaviour. A total of 300 focal sampling (6000 min), 3300 individual scan sampling (6000 min) and 62 group observations (1240 min) corresponding to the 100 mares were recorded. Non-parametric tests were used to analyse data. Results showed that experimental mares spent more time feeding (65.12% ± 2.40% v. 29.75% ± 2.45%, P < 0.01) and less time in locomotion (11.70% ± 1.31% v. 23.56% ± 1.34%, P < 0.01), stand resting (11.76% ± 2.57% v. 27.52% ± 2.62%, P < 0.01) and alert standing (5.23% ± 1.2% v. 14.71% ± 1.23%, P < 0.01). There was more bonding among experimental mares than control ones (26 v. 14, P < 0.05). Experimental mares showed more positive social interactions (P < 0.01) and less aggression (P < 0.01). These results suggest that giving densely housed mares foraging opportunities improves their welfare.

The use of a GnRH vaccine to suppress mare ovarian activity in a large group of mares under field conditions

The aim of this study was to evaluate the effect of active immunisation against GnRH on ovarian activity and serum progesterone concentrations in a large group of mares (10 control and 55 experimental) under field conditions as a model for wildlife species such as zebra and African elephants. Within the experimental group, mares were subdivided into three age categories: Category 1 (4 years and younger, n = 26), Category 2 (4–10 years old, n = 18), and Category 3 (≥11 years old, n = 11). Experimental mares were vaccinated intramuscularly with 2 mL (400 μg) of the GnRH vaccine Improvac (Pfizer Animal Health, Sandton, South Africa). Control mares received the same amount of saline solution. The vaccinations were repeated 35 days later. The ovaries and reproductive tracts of each mare were examined by means of rectal palpation and ultrasonography on Days 0, 35 and 70. Blood was collected weekly for determination of serum progesterone concentration until Day 175. On Day 35 after primary vaccination all of the control mares and 14.5% of the experimental mares showed evidence of ovarian activity on the basis of clinical examination and serum progesterone concentration. On Day 70, all control mares and none of the experimental mares showed evidence of cyclic activity. No age-related effect within treatment groups was found. The serum progesterone concentration indicated that all experimental mares remained in anoestrus until Day 175. Five of the control mares fell pregnant between Days 35 and 70. The five non-pregnant control mares continued to cycle until the end of the observation period. Having achieved such promising results in this trial we now plan to test the GnRH vaccine in Burchell’s zebra mares and African elephant cows.

Alteration in uterine contractility in mares with experimentally induced placentitis.

An experimental model of ascending placentitis was developed in the mare to characterize the uterine myoelectrical pattern in late gestation and determine how ascending placentitis altered this pattern. In experiment 1, myometrial electrical activity was analyzed during the early morning, late morning and evening hours in four mares in the last 15 days of gestation to identify patterns of activity. In experiment 2, nine mares received intra-cervical inoculations of Streptococcus equi subspecies zooepidemicus. Myoelectrical activity in the early morning and evening hours in these mares was compared with four control mares. In experiment 1, the number of spike burst clusters >30 s was greater in the evening than in the late morning hours (P < 0.04). Spike burst activity (number x duration) of mares in experiment 1 was similar during day and night recordings until the last 6 days of gestation when it gradually increased each evening until parturition (P < 0.05). In experiment 2, control mares experienced a gradual increase in the number of small spike burst clusters in the last 6 days (P = 0.008) and an increase in large and small spike burst clusters in the evening hours in the last 4 days of gestation (P = 0.03). Mares with experimentally induced placentitis never exhibited a rise in spike burst clusters but had an increase in the mean duration and activity index of large spike burst clusters in the 4 days before parturition (P < 0.04). In conclusion, control mares had a progressive, reversible rise in myoelectrical activity at night in the week preceding parturition. This was not observed in mares with experimentally induced placentitis. They exhibited an increase in the intensity and duration of large spike burst clusters possibly in response to local inflammation.

Ovarian function and morphology in the mare after multiple follicular punctures.

In the mare, ultrasound-guided transvaginal oocyte recovery and transfer might offer a way to circumvent the demanding procedures of in vitro embryo production. Before clinical application, the possible consequences for subsequent fertility have to be considered. To examine ovarian function and morphology in mares after repeated follicular punctures. A total of 14-26 follicular puncture sessions were conducted on each of 4 Norwegian pony mares over a period of 8 years. The ovaries of these mares were recovered by bilateral ovariectomy or at post mortem and subjected to macroscopic inspection and histology. For comparison, ovaries were collected from 7 nonaspirated control mares and processed for histology. In all experimental mares, ovarian function, defined as the ability regularly to ovulate preovulatory follicles and develop corpora lutea, remained normal during their last breeding season. Gross examination and histology showed that normal follicular and corpus luteum development was accompanied by the formation of condensed reparative fibrosis and normal local haemosiderosis of the ovarian stroma in all experimental mares. In one mare, an ovary contained several foci of chronic apostematous oophoritis, while a cystic structure lined with a single layer of epithelial-like cells and surrounded by a cartilaginous capsule was present in the other ovary. Repeated follicular aspirations do not hamper future folliculogenesis, ovulation and corpus luteum formation. However, ovarian puncture induces reparative fibrosis in the ovarian stroma and involves a risk of inducing abscess formation within the ovarian tissue which may impair fertility.

Immunization against GnRH in Mature Mares: Antibody Titres, Ovarian Function, Hormonal Levels and Oestrous Behaviour

The aim of the present study was to investigate the effect of active immunization against GnRH in mature Standardbred mares (three experimental and one control mare) on antibody titres, ovarian function, hormonal levels and oestrous behaviour. The mares were individually teased with a stallion once each day. During the first part of the experiment (period I: late April until November), blood was sampled every third day during the first 3 months, thereafter once per week. In the second part of the experiment (period II: December until August), sampling was carried out every second week. Progesterone, oestradiol-17beta and LH were analysed. Rectal gynaecological examination was made with the same intervals as the blood samplings and included palpation of the genital organs and ultrasonography. The experimental mares were immunized against GnRH with a GnRH-BSA conjugate. Equimune (Vetrepharm, Bracetown, Business Park, Clonee, Co. Meath, Republic of Ireland) was used as adjuvant. The mares were immunized on four occasions (20-30 day intervals) and GnRH antibody titre was determined. All immunized mares produced antibodies against GnRH but the maximum titres as well as the duration of a greater than 10% binding capacity varied between the mares (1 : 1600 to 1 : 50 000; 5 to 12 months, respectively). After the first injection, all mares showed one oestrus and ovulated at the regular time. In two of the mares, the immunization resulted in ovarian atrophy. Their hormone levels of progesterone, oestradiol- 17beta and progesterone decreased to basal levels and the cyclical hormone pattern was interrupted from approximately 30 days onwards. They continued to show oestrous signs but with irregular durations and intervals. The third mare showed ovarian suppression only for short periods and not in both ovaries at the same time; the hormone levels were basal for only about 20 days (days 50-70) and the mare ovulated on day 75 after start of immunization. The other mares ovulated after 13.5 and 15 months, respectively. It is concluded that the effect of immunization against GnRH in mature mares was individual concerning antibody titre response and the suppression of ovarian activity and hormone levels. Mares with totally inactive ovaries continued to show oestrous signs but with irregular intervals and durations.

Studies on the effect of manual massage of the ovaries on the reproductive activity of the mare

The aim of this study was to determine the influence of hand massage of mares' ovaries on breeding activity and hormonal changes in the winter anestrous period and during the luteal phase of the oestrus cycle. The experiment was conducted on 5 experimental and 5 control mares. In winter, (January) the experimental mares underwent 30-sec daily massage of both ovaries, for 30 d, and in summer (August) from the 6th day of the cycle to the occurrence of estrus. The sexual behavior of all mares was determined each day by individual teasing by a vigorous stallion, and the ovaries were checked by palpation per rectum and with an USG. Every second day blood samples were drawn from each mare to determine progesterone and estradiol in the plasma. Ovarian massage during deep winter anestrus had no significant effect on acceleration of the mares' active breeding season. Nevertheless, a higher concentration of estradiol was observed in the experimental group. These differences occurring on the 11th, 17th and 20th days were found to be significant (P ≤ 0.05). It was shown that during the summer period, in the luteal phase of the cycle, ovarian massage shortened the length of the estrous cycle, and ovulation was brought on somewhat earlier.

Work in progress: A simple technique that may improve the rate of embryo recovery on uterine flushing in mares

Embryo recovery rates from uterine flushings of normal mares on Day 7 or later after ovulation currently range from 55% to 80%. In contrast, pregnancy rates at 14 d in experimental mares are often higher. There appears to be a discrepancy between pregnancy rates and recovery rates of embryos on uterine flushing, indicating that some embryos are not recovered from the uterus on flushing. Per rectum ultrasound examination of the uterus of mares during flushing suggested that in some mares, the infused fluid may accumulate in the uterine body and not extend to contact the entire uterus, even after massage of the filled uterus per rectum. To increase embryo recovery rates, the flusing technique was altered to allow 3 min contact time of the flush fluid with the uterus during each of three flushes. It was thought that during this time, if the embryo was not directly contacted by the infused fluid, mobility of the embryo might cause it to move into the fluid, and thus be collected. This technique was used in 20 flushes on 14 mares, from 7 to 11 d after ovulation. Embryos were recovered on 18 of the 20 flushes. A total of 21 embryos was recovered, for an embryo recovery rate of 105%. The recovery rate from mares with single ovulations was 13/15 (87%); the recovery rate from mares with multiple ovulations was 8/5 (160%). These rates appear to be higher than those obtained previously in our laboratory and those reported by other workers in the field. These results indicate that further investigation into the efficacy of this procedure is warranted.

Postpartum LH profile characterisitics, estrus and ovulation: The influence of short-term foal removal

Summary This study was conducted to determine if equine luteinizing hormone (LH) is secreted in an episodic fashion early postpartum and if short-term foal removal affects the secretion pattern of LH and the interval to foal heat and ovulation. Pony mares foaling in May, June, and July were assigned to either a control group or a group whose foals were removed for 24 hours on Day 3 to 4 postpartum. Blood samples were collected via jugular venipuncture for alternate 6 hour periods for 48 hours beginning on Day 3. Samples were assayed for plasma LH concentrations via a radioimmunoassay. 16 . During the experimental period mares were bled and exposed daily to a stallion to determine estrus and ovulation. Samples were assayed for progesterone concentrations via a validated radioimmunoassay. 16 LH profile characteristics were identified by Merriam and Wachter's pulsar program 12 modified for personal computer use. 8 Episodic bursts of LH were detected in all early postpartum mares. In some 6-hour time blocks, episodic bursts occurred frequently. In other 6-hour blocks, episodic bursts occurred but were followed or proceeded by a lapse with no bursts. In still other 6-hour blocks, no episodic bursts were detected. Mean number, frequency and amplitude of LH bursts, mean LH concentration, maximum LH concentration, and duration of LH bursts for control and foal removal groups were similar (P>.10). The intervals from parturition to first day of estrus and to day of ovulation were similar (P>.10) for both groups, as was the duration of first postpartum estrus. The interval from 1st estrus to 2nd estrus postpartum was also similar (P>.0) for both groups. These data suggest that short-term foal removal had little effect on the episodic secretion of LH.

Development of a model to study endometritis in mares

Summary Endometritis is a significant reproductive disease resulting in reduced fertility. Ovarian hormones are known to affect certain aspects of uterine defense mechanisms and this premise was used to develop a model of endometritis. Ovariectomized or reproductively intact mares were treated with dexamethasone (40mg), progesterone (150mg) or a combination of progesterone and dexamethasone to suppress uterine defense mechanisms. Mares were then inoculated intrauterinely with Streptococcus zooepidemicus. Mares were monitored for endometritis by complete reproductive evaluation on Days 3, 7, 14, 21, 35 and 49 following inoculation. All mares had significant infectious and inflammatory changes during the reproductive evaluation immediately after inoculation. These changes resolved within 14 days in mares treated with dexamethasone only. Mares treated with progesterone or a combination maintained uterine infection as long as progesterone was continued. Use of systemic progesterone throughout the experimental protocol allowed consistent development of endometritis in intact experimental mares. This established a uniform population of experimental mares for further research on the pathogenesis of and treatment for endometritis.