Untreated Mares Research Articles

Progesterone Device Use Improves Ovum Pick-Up Efficiency in Acyclic Donors

The aim of this study was to evaluate follicular dynamics and ovum pick-up (OPU) efficacy in untreated mares or mares treated with an intravaginal progesterone (P4) device during seasonal anestrus (acyclic) and during the breeding season (cyclic). Six mares (mean age = 5 years), were recruited into an ovum pick-up scheme that was performed every 14 days with and without the P4 device, during the acyclic and cyclic phases. Aspirations amounted to seven procedures with or without the P4 device during each phase. Five ultrasound assessments were performed at each interval between the OPUs. Data on follicular number and diameter as well as the numbers of recovered and the percentage of recovered oocytes were also collected. The number of follicles from mares in the acyclic phase was higher (P < .005) regardless of the treatment. However, the follicular diameter was smaller for the P4 group (P < .005) from the 2nd to the 5th evaluation post-OPU procedure. The percentage of oocytes recovered during the acyclic phase was higher for mares treated with the P4 device (P < .005). The P4 device resulted in follicles with smaller diameters and facilitated OPU efficacy.

Parasite dynamics in untreated horses through one calendar year

BackgroundHorses are host to a plethora of parasites. Knowledge of the seasonality of parasite egg shedding and transmission is important for constructing parasite control programs. However, studies describing these patterns are sparse, and have largely been conducted only in the United Kingdom. This study evaluated strongylid egg shedding patterns and transmission dynamics of Strongylus vulgaris in naturally infected and untreated mares and foals through one calendar year in Kentucky, USA. The study also investigated the existence of a peri-parturient rise (PPR) in strongylid egg counts in foaling mares and collected information about Strongyloides westeri and Parascaris spp. in the foals.MethodsThis study was conducted from January to December 2018. A herd of 18 mares, one stallion, and 14 foals born in 2018 were followed throughout the year. Sera and feces were collected biweekly from all horses, and worm burdens enumerated in 13 foals at necropsy. An S. vulgaris ELISA antibody test was run on all serum samples. Fecal egg counts were determined for all horses, and coproculture and qPCR assay were employed to test for the presence of S. vulgaris in the mature horses. Data were analyzed using the proc glimmix procedure in the SAS 9.4 software program.ResultsWe found a general lack of seasonality in strongylid egg shedding throughout the year among the mature horses, and no PPR was demonstrated. Shedding of S. vulgaris eggs displayed a higher abundance during the spring, but findings were variable and not statistically significant. Anti-S. vulgaris antibody concentrations did not display significant fluctuations in the mature horses, but evidence of passive transfer of antibodies to the foals was demonstrated, and foals assumed their own production of antibodies starting at approximately 20 weeks of age. Overall, colts shed higher numbers of strongylid, ascarid, and S. westeri eggs than fillies.ConclusionsThis study demonstrated a lack of seasonality in strongylid egg shedding for the study population, which is in stark contrast to previous studies conducted elsewhere. This strongly suggests that more studies should be done investigating these patterns under different climatic conditions.Graphical

Oral misoprostol does not hasten oviductal transport of day-5 horse embryos

In horses, prostaglandin E2 (PGE2) is produced by embryos around Day 5 post-ovulation; PGE2 functions directly at the oviduct promoting embryo transport into the uterus. Non-surgical collection of horse embryos for cryopreservation is recommended at Day 6.5–7 post-ovulation. It was proposed that misoprostol administered orally will hasten oviductal transport of horse embryos. In Experiment 1 (n = 15) there was comparison of time of embryo recovery (Day 6 and 6.5 post-ovulation) from mares administered misoprostol (Day 5 and 5.5) orally to that of untreated mares. On Day 6, embryo collections were attempted; if no embryo was collected, there was a second attempt on Day 6.5. In Experiment 2, (n = 16) misoprostol treatment was initiated on Day 4.5; there was the first embryo collection attempt on Day 5.5, followed by Day 6 and 6.5 if no embryo was collected. Blood samples were collected at 12 h intervals on Day 4.5 or 5, to Day 6.5. In Experiment 1, on days 6 and 6.5, respectively, there was collection of seven and one of a total of eight embryos detected at the time of collection per group (P = 1). In Experiment 2, 12 embryos were collected during 15 cycles with there being a total of three, two, and one collected from mares of both groups on Day 5.5, 6, and 6.5 post-ovulation, respectively (P = 1). Serum progesterone concentrations were not different (P ≥ 0.05). In conclusion, misoprostol, when administered orally, does not hasten oviductal transport of horse embryos.

Fluoroquinolone exposure in utero did not affect articular cartilage of resulting foals.

Recent studies have shown that fluoroquinolones, specifically, enrofloxacin and its active metabolite (ciprofloxacin), cross the equine placenta without causing gross or histological lesions in the first and third trimester fetuses or resulting foal. However, it is possible that in utero exposure to fluoroquinolones may cause subtle lesions not detectable by standard means; thus, a more in-depth assessment of potential toxicity is warranted. To use quantitative magnetic resonance imaging (qMRI), biomechanical testing, and chondrocyte gene expression to evaluate the limbs of foals exposed to enrofloxacin during the third trimester of pregnancy. In vivo and control terminal experiment. Healthy mares at 280days gestation were assigned into three groups: untreated (n=5), recommended therapeutic (7.5mg/kg enrofloxacin, PO, SID, n=6) or supratherapeutic (15mg/kg, PO, SID, n=6) doses for 14days. Mares carried and delivered to term and nursed their foals for ~30days. Two additional healthy foals born from untreated mares were treated post-natally with enrofloxacin (10mg/kg PO, SID, for 5days). By 30days, foal stifles, hocks, elbows, and shoulders were radiographed, foals were subjected to euthanasia, and foal limbs were analysed by quantitative MRI, structural MRI, biomechanical testing and chondrocyte gene expression. Osteochondral lesions were detected with both radiography and structural MRI in foals from both enrofloxacin-treated and untreated mares. Severe cartilage erosions, synovitis and joint capsular thickening were identified in foals treated with enrofloxacin post-natally. Median cartilage T2 relaxation times differed between joints but did not differ between treatment groups. A small sample size was assessed and there was no long-term follow-up. While further research is needed to address long-term foal outcomes, no differences were seen in advanced imaging, biomechanical testing or gene expression by 30days of age, suggesting that enrofloxacin may be a safe and useful antibiotic for select bacterial infections in pregnant mares.

Rising up to the challenge of their rivals: Mare infidelity intensifies stallion response to playback of aggressive conspecific vocalizations

Management tools like immunocontraception can alter the behavior of target animals, but the extent to which they affect non-target individuals has received less attention. The feral horse (Equus caballus) population on Shackleford Banks, North Carolina is an ideal system with which these questions may be explored, as management of the population with the immunocontraceptive agent porcine zona pellucida (PZP) has resulted in an increased propensity for females to change social groups and thus, decreased social stability. During the study, on average, females made 1.4 group changes per day (range = 0–18.5 group changes per day): females previously treated with PZP made 1.8 group changes per day, while females that had never been treated made 1.2 group changes per day. Between May and August 2017, we used playbacks of aggressive male vocalizations (squeals) and human voices (reciting “hello horse”) to assess changes in stallion responses to male rivals versus socially irrelevant stimuli in the context of female turnover. Over the course of the study, males were observed for 9.4 h on average (range = 2.4–20.5 h). Males spent more time vigilant (estimate = 12.431, P = 0.016, x¯squeal = 30 s, x¯control = 19 s) and were more likely to approach the speaker following squeal playbacks than controls (estimate = 2.325, P = 0.039). Males’ latency to return to normal behaviors varied depending on whether the playback was conducted in the weeks before, during, or after group changes occurred (P = 0.025, x¯before = 26 s, x¯during = 39 s, x¯after = 53 s). Male responses were not affected by the total number of female group changes a male experienced during the observation period (P > 0.4), suggesting the effects are more context-dependent and not long-lasting. These findings suggest mare turnover can impact stallion responsiveness to potential rivals. As previously contracepted mares change groups more often than untreated mares and stallions exhibit prolonged responses to aggressive vocalizations after experiencing a female group change, contraception-induced changes to mare behavior may lead to increased male aggression in response to intruding rivals, which could be associated with greater energy expenditure. Finally, our work demonstrates that playback experiments are a useful tool for studying feral horse behavior in the wild. As the need for population control of different species continues to expand, rigorous investigations of immunocontraception’s effects on non-target animals are critical if agencies are to manage populations most effectively.

Diffusion of fluoroquinolones into equine fetal fluids did not induce fetal lesions after enrofloxacin treatment in early gestation

While recent work demonstrated that enrofloxacin and ciprofloxacin reach the fetoplacental unit without causing obvious lesions in the 9-month-old equine fetus or resulting foal, many practitioners still hesitate to prescribe a fluoroquinolone during pregnancy. Since early gestation is a critical time for fetal skeletal development, if fluoroquinolones are chondrotoxic to the fetus at any point during gestation, this period would be important. The aim of this study was to assess the effects of 2 weeks’ exposure to enrofloxacin on the equine fetus between 46 and 60 days gestation. Twelve pregnancies from nine healthy mares were allocated into two groups: untreated (n=7), or treatment (7.5mg/kg enrofloxacin, PO×14days, n=6). Abortion was induced with prostaglandin 24h after the last enrofloxacin dose, or on the equivalent day of gestation for untreated mares. Four of nine mares were rebred for a second cycle and were assigned to the opposite treatment to serve as their own controls. Fetal fluids from treated mares were analysed for enrofloxacin and ciprofloxacin concentrations. Fetal organs (heart, lungs, spleen, kidney, and liver) and limbs were examined histopathologically.Enrofloxacin and ciprofloxacin diffused to the fetal fluids during early gestation and did not result in detectable abnormalities in the fetus after 14 days of treatment. While current research does not determine long-term foal outcomes, enrofloxacin may be useful for select bacterial infections in pregnant mares.

Efficacy of dart-delivered PZP-22 immunocontraceptive vaccine in wild horses (Equus caballus) in baited traps in New Mexico, USA

Abstract Context Federally protected wild horses on public lands are undergoing population growth that overwhelms the historical management strategy of removal and adoption. Porcine zona pellucida (PZP) has been used as an injectable immunocontraceptive vaccine to induce reversible infertility in free-roaming horses. PZP vaccination during February and March, which is the optimal time for administering current vaccines, is not possible for the herd on Jarita Mesa Wild Horse Territory (JM WHT), New Mexico, due to severe weather, terrain and subject wariness. AimsThe first goal was to assess bait trapping and remote darting as a minimally disruptive alternative to helicopter gathers for treatment. The second goal was to quantify the efficacy over 2 years following spring treatment with a single injection of PZP-22 (a combination of PZP-adjuvant emulsion and controlled-release pellets) by remote dart delivery. Methods Bait trapping and dart delivery of PZP-22 was carried out on JM WHT from 4 April to 16 June 2012. The herd was observed in the summers of 2011, 2013 and 2014 to determine the foaling status of the study mares. Outcome (foal or no foal) as a function of treatment was analysed using Fisher’s exact test. Key resultsThere were 157 individuals, including 66 females &amp;gt;1 year old, documented in 2011. In 2012, 26 females (including three yearlings) identified by colour and markings were bait trapped and darted with PZP-22. The proportion of treated females foaling was lower than that of untreated females in 2013 and 2014, but the difference was only significant in 2013. Of the treated mares observed in 2013, the two that foaled were the last two treated in 2012. Untreated mares &amp;gt;4 years old were significantly more likely to foal than younger mares. Conclusions Bait trapping at JM WHT permitted successful delivery of PZP-22 in a previously inaccessible herd. Dart administration of PZP-22 in April–June induced at least 1 year of measurable infertility. Implications This is the first demonstration of the efficacy of an initial treatment of PZP-22 delivered by dart instead of hand injection. Considerations for PZP-22 treatment include seasonal timing of treatments and age of treated mares. Treatments need to take place early enough to allow antibody titers to build to contraceptive levels before the breeding season.

Lingering effects of contraception management on feral mare (Equus caballus) fertility and social behavior.

Due to the extirpation of their natural predators, feral horse populations have expanded across the United States, necessitating their management. Contraception of females (mares) with porcine zona pellucida (PZP) is a popular option; however, effects to physiology and behavior can be substantial. On Shackleford Banks, North Carolina, USA, treated mares have exhibited cycling during the non-breeding season and demonstrated decreased fidelity to the band stallion, but PZP's long-term effects on mare physiology and behavior remain largely unexplored. After the contraception program was suspended in this population, we examined how prior exposure to varying levels of PZP treatment impacted (1) foaling probability and foaling dates (a proxy for ovulatory cycling) from 2009 to 2014 and (2) mare fidelity to the band stallion and reproductive behavior during 2013 and 2015. Additionally, we evaluated the effects of time since the mares' last treatment on these factors. Mares receiving any level of prior PZP treatment were less likely to foal than were untreated mares. Among mares that received 1-3 PZP applications, foaling probability increased with time since last treatment before declining, at ~6 years post-treatment. Mares that received 4+ applications did not exhibit a significant increase in foaling probability with time since last treatment. Moreover, previously treated mares continued to conceive later than did untreated mares. Finally, mares previously receiving 4+ treatments changed groups more often than did untreated mares, though reproductive behavior did not differ with contraception history. Our results suggest that although PZP-induced subfertility and its associated behavioral effects can persist after the cessation of treatment, these effects can be ameliorated for some factors with less intense treatment. Careful consideration to the frequency of PZP treatment is important to maintaining more naturally functioning populations; the ability to manage populations adaptively may be compromised if females are kept subfertile for extended periods of time.

Influence of acidity on the mechanical stability of retouched Japanese tissue papers during the course of artificial ageing

This study investigates the relationship between acidity and the mechanical properties of two Japanese tissue papers (Yukyu-shi and Sekishu Mare), which were treated with a range of plant dyes, watercolours and acrylic paints and then exposed to artificial ageing. Mechanical strength was correlated with the concentration of hydrogen ion (pH) which is an index of the acidic hydrolysis of cellulose in paper structure. In general, the papers treated with plant dyes were more acidic than those treated with watercolours and acrylic paints. Plant-dyed Japanese papers also displayed less folding and tear resistance after ageing and there was a difference in these properties in both of these papers. The untreated Sekishu Mare papers, as well as those treated with watercolours and acrylic paints, exhibited greater tear resistance than the Yukyu-shi papers treated in the same conditions. The Sekishu Mare and Yukyu-shi papers, both untreated and treated with acrylic paints, as well as the Yukyu-shi papers treated with plant dyes, suffered no loss of folding endurance after ageing, which was unexpected considering that the papers were aged for 12 days at 70°C and 65% relative humidity (RH). This study provides paper conservators with a better understanding of toning materials and their impact on the mechanical and chemical stability of papers often chosen for conservation treatments.

Progesterone levels and days to luteolysis in mares treated with intrauterine fractionated coconut oil

Intrauterine plant oil infusion, including fractionated coconut oil, has been previously found to be a safe, inexpensive, and reversible method of prolonging the luteal phase in mares when administered on Day 10 of the estrous cycle. Our objective was to understand the uteroovarian response to the administration of fractionated coconut oil infusion in the uterus of diestrous mares. We hypothesized that intrauterine coconut oil administration on Day 10 would prolong luteal life span in a dose-dependent fashion and would result in higher serum progesterone levels than untreated mares at the expected time of luteolysis. Light-horse mares (n = 18) were examined using transrectal palpation and ultrasonography to determine if they had a normal interovulatory interval and were then examined daily in estrus until the day of ovulation (Day 0) and then every other day during an estrous cycle. Jugular blood was drawn on Day 11, Day 13, Day 15, and Day 17, centrifuged, and serum stored until assayed for progesterone (P4; Siemens Coat-a-Count Progesterone RIA, Los Angeles, CA, USA). Mares were randomly assigned to treatment and studied over one to two estrous cycles with a rest cycle after each treatment cycle. Groups were: control (n = 5), fractionated coconut oil 1.0 mL (Miglyol 810; Sasol Oil, Witten, Germany) infused in the uterus with an artificial insemination pipette on Day 10 (Group 1; n = 5) and fractionated coconut oil 0.5 mL infused in the uterus with an embryo transfer gun, on Day 10 (Group 2; n = 5). All statistical analyses were performed using analytical software (Stata SE, version 13.1, College Station, TX, USA) at P < 0.05. Data were first evaluated using the Shapiro–Wilk test for normality. Differences between groups in days to luteolysis (DTL) were examined using analysis of variance and Bonferroni, and the effect of day and treatment on P4 levels were examined using the Kruskal–Wallis and Dunn's all pairwise test. There was a significant difference in DTL between the groups (P = 0.0083), with fewer DTL in Group 1 compared to control (P = 0.011) and to Group 2 (P = 0.034). There was a significant effect of day (P < 0.0001) on P4 levels with Day 11 P4 levels higher than Day 15 and Day 17 and Day 13 P4 levels higher than Day 15 or Day 17 (P < 0.03). There was a significant effect of treatment group (P = 0.0098) on P4 levels with control and Group 2 levels higher than Group 1 mares (P = 0.0012, P = 0.0495, respectively). We concluded that intrauterine administration of 1 mL of fractionated coconut oil lowered P4 levels in diestrus in a dose-dependent fashion and did not prolonged the luteal phase of the mares.

Proteomics of endometrial fluid after dexamethasone treatment in mares susceptible to endometritis

Corticotherapy is a common treatment in mares susceptible to endometritis. Isoflupredone improves pregnancy rates and affects the protein profile of endometrial fluid in comparison to untreated mares. Dexamethasone decreases postbreeding fluid accumulation and uterine edema; however, its effects on the protein profile of the endometrial fluid have not yet been studied. The aim of the present study was to verify the effect of dexamethasone on the protein profile of endometrial fluid, in the presence or absence of infection, from mares susceptible to persistent postbreeding endometritis. Nine susceptible mares aged between 7 and 18 years were used. After checking for signs of estrus, mares were subjected to four treatments: C: mares received no treatment and served as control; D: mares received 40-mg dexamethasone at breeding, with collection of samples after 6 hours; I-6 and I-24: intrauterine infusion of 1 × 109Streptococcus zooepidemicus/mL and samples collected after 6 and 24 hours; I/D-6 and I/D-24: intrauterine infusion of 1 × 109S zooepidemicus/mL and 40-mg dexamethasone, collecting the sample after 6 and 24 hours. All mares were subjected to all treatments. Samples were collected and subjected to two-dimensional electrophoresis and mass spectrometry for the identification of relevant protein spots. Corticotherapy altered the protein profile of the endometrial fluid of susceptible mares, characterized by an increase and/or decrease in the optical density of inflammatory acute-phase proteins. We conclude that the use of dexamethasone in mares with and without infection alters the protein profile of endometrial fluid of susceptible mares.

Treatment with human chorionic gonadotrophin before ovulation increases progestin concentration in early equine pregnancies

For prevention of early conceptus loss in the horse, treatment with progestins has become common practice. In cattle, treatment with human chorionic gonadotrophin (hCG) during the early postovulatory phase stimulates endogenous progesterone synthesis, which is an important factor for maintenance of early pregnancy via stimulation of endometrial function and conceptus development. In the present study we have therefore investigated the influence of treatment with hCG either for induction of ovulation or during the early luteal phase on plasma progestin concentrations, size of the corpus luteum and size of the conceptus in early pregnant mares. We hypothesized that hCG treatment stimulates progestin secretion and conceptus development. In Experiment 1, induction of ovulation with hCG (1500IU i.v.; n=14) significantly increased progestin concentration between days 5 and 15 after ovulation compared to untreated controls (n=28; p<0.05; e.g. day 5 hCG i.v.: 17.2±1.9, control: 13.9±0.8ng/ml). A significant interaction (p<0.05) of hCG treatment with size of the conceptus between days 30 and 40 of pregnancy was detected. In Experiment 2, treatment of mares with hCG (5000IU) on day 5 after ovulation (n=12) did neither affect progestin secretion (e.g. day 8 hCG: 15.4±1.6, control: 17.6±1.2ng/ml) nor luteal tissue area (e.g. day 8 hCG: 9.0±0.7, control: 7.6±1.4cm2) compared to untreated mares (n=9). In conclusion, treatment of mares with hCG for induction of ovulation within 48h before ovulation but not on day 5 of the luteal phase stimulates progestin secretion and may enhance conceptus development via stimulation of endometrial function during early pregnancy.

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.

Linking social environment and stress physiology in feral mares (Equus caballus): Group transfers elevate fecal cortisol levels

Feral horses (Equus caballus) have a complex social structure, the stability of which is important to their overall health. Behavioral and demographic research has shown that decreases in group (or band) stability reduce female fitness, but the potential effects on the physiological stress response have not been demonstrated. To fully understand how band stability affects group-member fitness, we need to understand not only behavioral and demographic, but also physiological consequences of decreases to that stability. We studied group changes in feral mares (an activity that induces instability, including both male and female aggression) on Shackleford Banks, NC. We found that mares in the midst of changing groups exhibit increased fecal cortisol levels. In addition, mares making more group transfers show higher levels of cortisol two weeks post-behavior. These results offer insights into how social instability is integrated into an animal’s physiological phenotype. In addition, our results have important implications for feral horse management. On Shackleford Banks, mares contracepted with porcine zona pellucida (PZP) make approximately 10 times as many group changes as do untreated mares. Such animals may therefore be at higher risk of chronic stress. These results support the growing consensus that links between behavior and physiological stress must be taken into account when managing for healthy, functional populations.

Serum amyloidAconcentration in healthy periparturient mares and mares with ascending placentitis

Placentitis is a prevalent cause of abortion, premature delivery and neonatal death in mares. Early diagnosis is paramount for the survival of the fetus and delivery of a live foal. To determine: 1) Serum amyloid A (SAA) profile in healthy mares during late gestation; 2) if placentitis affects SAA concentrations and 3) the effects of therapy on SAA concentrations and pregnancy outcome in mares with placentitis. In Experiment I, 15 healthy pregnant mares were evaluated from 280 days of gestation to 60 h post partum. In Experiment II, pregnant mares were inoculated intra-cervically with Streptococcus zooepidemicus (Day 280-295) and assigned to control (n = 5) and treatment (n = 9) groups. Treatment was initiated at the onset of clinical signs. Serum amyloid A concentrations were determined prior to inoculation and then weekly until abortion or delivery. Serum amyloid A remained at low concentrations (95% confidence interval [CI]: 3.2-8.1 mg/l) during late gestation followed by a significant increase within 36 h post partum; SAA returned to basal concentrations by 60 h post partum. In Experiment II, SAA significantly increased within 96 ± 56 h of inoculation in control mares followed by abortion. Therapy was effective (P<0.05) in preventing the rise in SAA in 66% (6/9) of mares and only one out of 3 mares with increased SAA aborted. Overall, the incidence of abortion was higher in mares with increased SAA concentrations (75%; 6/8) compared with mares in which SAA remained at baseline concentrations (0/6). Mares with placentitis had significant increased SAA within 96 h post inoculation and concentrations remained increased until abortion in untreated mares. Successful treatment either prevented the rise of SAA concentration or decreased its concentration to baseline concentrations, followed by delivery of a live foal. Serum amyloid A may be used as a prognostic indicator in cases of ascending placentitis in the mare.

12 PROGESTERONE SUPPLEMENTATION DAY 3 TO 5 POST-OVULATION IN AI-BRED MARES

The purpose of this study was to determine the effectiveness of increasing progesterone (P4) concentrations during early pregnancy, by supplementing a low dose of Regu-Mate® (Intervet, Millsboro, DE, USA) on Days 3, 4, and 5, post-ovulation to AI mares. Sixty-three AI-bred mares were randomly allocated to 1 of 2 treatment groups. All mares underwent ovulation induction using 1.5 mg mL–1 of deslorelin acetate (IM) following observation of ≥30-mm follicles and were inseminated with either fresh (n = 57) or cooled (n = 6) semen from fertile stallions approximately 24 h later. Ovulation was verified via ultrasonography in all mares. Mares allocated to the treatment group (n = 29) received altrenogest (Regu-Mate®) orally at a rate of 15 mg per day on Days 3, 4, and 5 following ovulation (d = 0), whereas control mares (n = 34) received no treatment. Blood samples were collected from all mares from Day 0 (ovulation) through Day 6 post-ovulation via jugular venipuncture. Pregnancies were determined via ultrasonography at 18 days post-ovulation. The pregnancy rate for untreated mares (18/34, 53%) was not different (P &gt; 0.05) from altrenogest-treated mares (13/29, 45%). There was no difference (P &gt; 0.50) in pregnancy rates when mares were AI bred 1 (19/39, 49%) or 2 (10/20, 50%) days from ovulation. The mean plasma P4 concentration on Day 5 was higher (P &lt; 0.06) for pregnant control mares (4.75 ± 0.59 ng mL–1) compared with open control mares (3.50 ± 0.25 ng mL–1). There was a greater increase (P &lt; 0.02) in plasma P4 concentrations (Day 5 – Day 1 concentration) in untreated pregnant mares (3.87 ± 0.56 ng mL–1) compared with untreated open mares (2.38 ± 0.22 ng mL–1). In conclusion, it was determined that altrenogest supplementation from Day 3 to 5 post-ovulation was ineffective in improving pregnancy rates. However, it is unknown if this was the result of the dose used or the length of supplementation. Additionally, the timing of altrenogest coincided with a significant increase in P4 in pregnant mares compared with open mares, indicating that the timing may be correct or there was action of an unknown embryonic luteotropin(s), which would describe the differences between P4 concentrations in pregnant versus open mares.

The effect of platelet-rich plasma on endometrial pro-inflammatory cytokines in susceptible mares following semen deposition

Mares susceptible to persistent mating-induced endometritis (PMIE) are a source of substantial economic inefficiency. Recent studies report a significant post insemination up-regulation of endometrial anti-inflammatory cytokines IL-10 and IL-Ra in normal versus susceptible mares, as well as significantly increased and prolonged expression of IL-1b, IL-6, IL-8, and IL1Ra in susceptible mares following intrauterine inoculation with E.coli [1]. Furthermore, nitric oxide is suspected to play a significant role in uterine clearance, because increased endometrial expression of inducible nitric oxide synthetase (iNOS) has been reported in susceptible mares following insemination [2]. This project was developed to investigate the expression of inflammatory biomarkers of uterine biopsies obtained from susceptible mares following intrauterine PRP (platelet-rich plasma) infusion. Platelets contain alpha-granules that, upon activation, secrete bioactive molecules with regenerative capacity in the form of growth factors, cytokines, and chemokines. Barrenmares with a history of PMIE (n 1⁄4 9) underwent daily ultrasonographic examination of the reproductive tract per rectum while in estrus. All mares underwent an untreated (no PRP) cycle followed by a treated (PRP) cycle. When a dominant follicle >35 mm in diameter and evidence of endometrial edema were detected, 1.0 mg deslorelin acetate (SucromateR Bioniche Animal Health Pullman, WA) was administered intramuscularly. On the treatment cycle, 180 ml of citrated whole blood was obtained for PRP processing in a specialized blood fraction separating centrifuge system (Angel Cytomedix, Inc. Gaithersburg, MD). The resultant PRP was brought to a final volume of 10 ml with plateletpoor plasma and infused into the uterus. Mares were inseminated with >200 million motile sperm 24-36 hours following deslorelin administration. An endometrial biopsy obtained the following day was preserved in RNAlaterR (Sigma Inc., St Louis, MO) for reverse transcription polymerase chain reaction (RT–PCR) analysis [1] for mRNA expression of inflammatory biomarkers IL-1b, IL1-Ra, TNFa, IL-6, IL-8, IL-10, and iNOS. Data were analyzed using SAS (SAS Institute, Cory NC) with Wilcoxon signed-rank test (non-parametric). Comparisons were made between pretreatment and post-treatment groups. Significance was set to P < 0.05. In susceptible mares treated with an intrauterine infusion of PRP, the mRNA expression of IL-1b, IL-6, IL-8 and iNOS was significantly down-regulated (P < 0.05) when compared with untreated mares. All other cytokines were similar in treated and untreated mares. Therefore, following semen deposition, PRP influences the mRNA expression of endometrial pro-inflammatory cytokines and iNOS in mares susceptible to PMIE. References

Growth of the dominant follicle and endometrial folding after administration of hCG in mares during oestrus

The purpose of the trial was evaluation of follicular growth and endometrial folding in mares after human chorionic gonadotropin (hCG) treatment in comparison with untreated mares during oestrus. In addition, the influence of follicle size at the time of hCG treatment on these parameters was evaluated. HCG (3000 IU) was administered intravenously in 17 mares bearing dominant follicles 35&amp;ndash;40 mm in diameter (Group A) and in 13 mares with larger follicles (Group B). Ten mares with follicles &amp;ge; 35 mm were untreated (Group C). Ultrasonographical examination of the mares continued in 6 h intervals until ovulation. Growth of the dominant follicle was faster in Group A than in Groups B and C (1.3 vs. 0.3 and 0.7 mm/6h, P &amp;lt; 0.05) but diameters of the preovulatory follicles were similar &amp;ndash; 44, 48 and 44 mm in Groups A, B and C, respectively. Similarly, reduction of endometrial folding (on a three point scale) during observation was higher in Group A than in B and C (2.1 vs. 1.2 and 1.8, A : B P &amp;lt; 0.05) but endometrial folding values in the term before ovulation were not different (0.6, 0.9 and 0.6 in Groups A, B and C). A positive correlation between the speed of follicular growth and reduction of endometrial folding was found (r&lt;sub&gt;s&lt;/sub&gt; &amp;ndash; 0.479, P = 0.003). Irregularity in follicle shape (the difference between the longest axis and its perpendicular axis) at the beginning of observation (3.3, 4.0 and 3.2 mm) was lower than before ovulation (7.4, 10.4 and 9.2 mm) in all groups (P &amp;lt; 0.01). The interval from the beginning of observation until ovulation was significantly shorter in Groups A and B versus C (37 and 31 vs. 103 h, P &amp;lt; 0.01). The results show that growth of dominant follicles after hCG is influenced by the size of the follicles at the time of treatment and correlates with reduction in endometrial folding as well as irregularity of follicle shape. Nevertheless, hCG treatment does not influence the size and shape of preovulatory follicles or endometrial folding immediately before ovulation. &amp;nbsp;

Foaling rates in feral horses treated with the immunocontraceptive porcine zona pellucida

AbstractLocally abundant feral horses (Equus caballus) can rapidly deplete available resources. Fertility control agents present promising nonlethal tools for reducing their population growth rates. We tested the effect of 2 forms of the immunocontraceptive porcine zona pellucida (PZP) on foaling rates in 3 populations of feral horses in the western United States. A liquid form requiring annual boosters was administered at Little Book Cliffs Wild Horse Range, Mesa County (CO), and Pryor Mountain Wild Horse Range, Bighorn County (WY) and Carbon County (MT), and a time‐release pellet form designed to produce 2 yr of infertility was administered at McCullough Peaks Herd Management Area, Park County (WY). Average foaling rates (foals born/mare‐yr) from direct observation of untreated and treated female horses (mares), 2004–2008, were 60.1% (n = 153 mare‐yr) versus 6.6% (n = 91 mare‐yr) at Little Book Cliffs, and 62.8% (n = 129 mare‐yr) versus 17.7% (n = 79 mare‐yr) at Pryor Mountain, respectively. At McCullough Peaks, mean annual foaling rates from 2006 to 2008 were 75.0% (n = 48 mare‐yr) for untreated mares and 31.7% (n = 101 mare‐yr) for treated mares. Controlling for age of mares and pretreatment differences in fertility, PZP reduced foaling rates in all 3 herds. The pellets used at McCullough Peaks (produced by cold evaporation) were less effective than pellets used in a previous trial and produced by heat extrusion. Immunocontraception with PZP may be a useful tool in reducing fertility rates in some western United States feral horse herds, but population growth reduction will depend on timely access to mares for inoculation and the proportion of mares that can be successfully treated. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.

Systemic treatment with high dose of flunixin-meglumine is able to block ovulation in mares by inducing hemorrhage and luteinisation of follicles

Prostaglandins play an obligatory role during the process of ovulation in mammals. Ovulation can be blocked by intrafollicular administration of non-steroidal anti-inflammatory drugs (NSAIDs) in several domestic species including the mare as well as by systemic administration of these drugs in women. In the mare, the effect of systemic NSAIDs treatment on ovulation has not been critically studied. The objectives of this study were: a) to determine whether high dose of flunixin-meglumine (FM) administered systemically to mares during the periovulatory period was able to block ovulation; and b) to study the follicular ultrasound characteristics of FM treated mares. Six mares were used in the study during two consecutive estrous cycles. Each mare received 2 mg FM/kg i.v. twice a day starting at the time of treatment with hCG when the follicle reached a diameter of ≥ 32 mm and continuing until ovulation. During the consecutive control cycle (CON) the mares received the same dose of hCG but were not administered FM. During the FM cycles five of six mares failed to ovulate and collapse the preovulatory follicle; but echoic specks were observed within the follicles, which continued to grow until a mean diameter of 55 mm. Eventually, the follicular contents were organised and luteinised. All CON mares ovulated normally. In conclusion, when mares were treated with FM, they had a higher incidence of ovulatory failure and development of luteinised unruptured follicles (83%, P = 0.015) compared with untreated mares.