Tex S. Taylor

Mares with Delayed Uterine Clearance Have an Intrinsic Defect in Myometrial Function

Abstract Persistent, postmating endometritis affects approximately 15% of mares and results in reduced fertility and sizable economic losses to the horse-breeding industry. Mares that are susceptible to postmating endometritis have delayed uterine clearance associated with reduced uterine contractility. Unfortunately, the mechanism for reduced uterine contractility remains an enigma. The present study examined the hypothesis that mares with delayed uterine clearance have an intrinsic contractile defect of the myometrium. Myometrial contractility was evaluated in vitro by measuring isometric tension generated by longitudinal and circular uterine muscle strips in response to KCl, oxytocin, and prostaglandin F2α (PGF2α) for young nulliparous mares, older reproductively normal mares, and older mares with delayed uterine clearance. In addition, intracellular Ca2+ regulation was evaluated using laser cytometry to measure oxytocin-stimulated intracellular Ca2+ transients of myometrial cells loaded with a Ca2+-sensitive fluorescent dye, fluo-4. For all contractile agonists, myometrium from mares with delayed uterine clearance failed to generate as much tension as myometrium from older normal mares. Oxytocin-stimulated intracellular Ca2+ transients were similar for myometrial cells from mares with delayed uterine clearance and from older normal mares, suggesting that the contractile defect did not result from altered regulation of intracellular Ca2+ concentration. Furthermore, no apparent age-dependent decline was observed in myometrial contractility; KCl-depolarized and oxytocin-stimulated longitudinal myometrium from young normal mares and older normal mares generated similar responses. However, circular myometrium from young normal mares failed to generate as much tension as myometrium from older normal mares when stimulated with oxytocin or PGF2α, suggesting possible age-related alterations in receptor-second messenger signaling mechanisms downstream of intracellular Ca2+ release. In summary, for mares with delayed uterine clearance, an intrinsic contractile defect of the myometrium may contribute to reduced uterine contractility following breeding.

Techniques for evaluating selected reproductive disorders of stallions

Numerous techniques may be used for evaluation of the different reproductive disorders of the stallion. Approaches may vary from real-time ultrasonography and biopsy for evaluating testicular tumors to use of special assays for evaluating sperm or plasma for presence of antisperm antibodies. This communication addresses techniques used to evaluate five relatively uncommon, but perplexing, disorders of breeding stallions: (1) seminal vesiculitis, (2) hemospermia associated with idiopathic urethral defects, (3) acrosomal dysfunction, (4) abnormal spermatozoal chromatin, and (5) azoospermia.

Estrous cycle characteristics and response to estrus synchronization in mammoth asses (equus asinus americanus)

Breeding records from a herd of mammoth asses (Equus asinus americanus) maintained on pasture in southeast Texas from 1990 to 1998 were reviewed. Jennies were pasture or hand mated, and estrus was either observed while the jennies were on pasture or when exposed to a jack after being penned. Eighty-one estrus periods and 43 diestrus intervals were recorded in 33 jennies over 4 seasons of the year (January-March, April-June, July-September, and October-December). Estrous cycle length and the duration of estrus were similar among seasons. Over all seasons, estrous cycle length was 23.3 +/- 2.6 d, duration of estrus was 5.9 +/- 2.1 d, and diestrus length was 17.4 +/- 2.6 d (mean +/- SD). During these same 9 yr, 58 injections of PGF2 alpha (5 mg, i.m.) were administered to 38 jennies without regard to stage of estrous cycle. Seventy-six percent (44/58) of the jennies showed signs of estrus after PGF2 alpha treatment, with an interval to estrus of 4.4 +/- 1.6 d and a duration of estrus of 5.6 +/- 1.7 d. Two estrus synchronization schemes were also assessed. Trial 1 was performed in October to November 1996, and Trial 2 was performed in February to March 1998. In Trial 1 (Group PE + PGF, n = 10), each jenny was injected intramuscularly once daily for 10 d with 150 mg progesterone and 10 mg estradiol-17 beta in sesame oil, and PGF2 alpha (10 mg) was injected intramuscularly on the last day of treatment. In Trial 2 (Group PGF-2X, n = 11), each jenny was injected intramuscularly twice, 16 d apart, with 10 mg PGF2 alpha. All Group PE + PGF jennies responded to treatment. One jenny in Group PGF-2X did not respond to either injection of PGF2 alpha, while 2 jennies responded to the first but not the second PGF2 alpha injection (8 of 11 jennies returned to estrus and ovulated after the second PGF2 alpha injection). Duration of estrus was 6.8 +/- 1.9 d for Group PE + PGF and 7.1 +/- 1.8 d for Group PGF-2X jennies. Interval to estrus and interval to ovulation following the last treatment were 9.0 +/- 0.9 d and 14.5 +/- 1.7 d, respectively, in Group PE + PGF jennies, and 4.5 +/- 0.9 d and 10.4 +/- 1.8 d, respectively, for Group PGF-2X jennies. In summary, estrous cycle characteristics of mammoth asses are similar to those reported for standard jennies, and estrus synchronization schemes used in horses are effective in mammoth asses.

A comparison of three combinations of injectable anesthetics in miniature donkeys

OBJECTIVE To compare three combinations of injectable anesthetics in miniature donkeys for quality of induction, recovery, muscle relaxation, cardiopulmonary changes during anesthesia and duration of recumbency. Design  Prospective, randomized experimental study. ANIMALS Six miniature donkeys (< 90 cm in height at the withers) weighing 92-127 kg were used. MATERIALS AND METHODS The drug combinations were: xylazine-butorphanol-ketamine (XBK), xylazine-butorphanol-tiletamine-zolazepam (XBT) and xylazine-propofol (XP). Each miniature donkey was anesthetized with each combination at 1-week intervals in random order. Heart and respiratory rates, indirect blood pressure and temperature were measured before and at 5-minute intervals during recumbency. Arterial blood samples were drawn for blood-gas analysis before and at 5, 15 and 30 minutes of anesthesia when samples could be collected. Recumbency time to sternal and time to standing were recorded and a subjective evaluation of induction, muscle relaxation and recovery were made. RESULTS Mean recumbency time ± SD was 14.7 ± 9.4, 33.8 ± 6.3 and 14.6 ± 1.9 minutes with XBK, XBT and XP, respectively. Mean time to standing ± SD was 28.4 ± 11.3, 43.7 ± 7.2 and 26.3 ± 2.9 minutes with XBK, XBT and XP, respectively. Heart and respiratory rates and blood pressures varied from baseline but were always within normal ranges. Hemoglobin saturation, pH and PaO2 tended to be lower with these doses of XBT and XP. CONCLUSIONS AND CLINICAL RELEVANCE Overall quality of anesthesia was poor with XBK. At the doses used this combination did not provide sufficient anesthesia compared with the combinations of XBT and XP, which appeared to provide acceptable anesthesia of short duration in miniature donkeys.

Mammoth asses—selected behavioural considerations for the veterinarian

Abstract Observations of the behaviour of domestic mammoth and standard asses (donkeys) receiving routine herd health and therapeutic procedures are described. These procedures include capture, physical examination, restraint, medicating, adapting to hospitalization and training for interspecies breeding.

Physiologic responses during an exhaustive driving test in donkeys: effect of conditioning

Abstract Improvement in performance following a 1-month conditioning period was tested in five donkeys. The two females and three geldings weighed 235 kg (SD, 54) and were 4 to 8 years old. The donkeys had previously been trained to pull a cart and were accustomed to wearing heart rate monitors. Following resting readings of heart rate (HR), respiratory rate (RR), rectal temperature ( T ), and venous lactate samples, the donkeys were driven to the cart with a draft load equal to 21% body weight, at a trot, until exhausted (defined as when they would not continue trotting). Time to exhaustion, distance and speed were measured. HR was recorded at 5-min intervals during the test and at 1, 5, 10, 20, 30 and 60 min after the test ended. T , RR and lactate were measured at 30-min intervals during the test and at 1, 5, 10, 20, 30 and 60 min post-test. The donkeys were then conditioned for 1 month by being driven 3×/week for 90 min, with a draft load equal to 15% body weight, and weekly increases in trotting time. Donkeys were then re-tested as before conditioning. Resting HR decreased significantly post-conditioning. Working HR values were lower and post-exercise HR decreased to resting rate post-conditioning. Lactate increased 3-fold pre-conditioning, but only by 50% post-conditioning. Average distance covered post-conditioning was increased by 67% (from 12.7 to 21.2 km), while time to exhaustion increased by 86% (from 84 to 155 min). Donkeys worked under conditions of high ambient temperate and humidity: temperatures ranged from 29 to 34°C while humidity ranged from 43 to 65%. Conditioning significantly increased the donkeys apparent productivity (as measured by distance covered).

Nephrectomy via ventral median celiotomy in equids.

OBJECTIVE To report technique for, and outcome after, nephrectomy through a ventral median celiotomy in equids. STUDY DESIGN Case series. ANIMALS Equids with unilateral renal disease (n = 6), aged 2 months to 18 years, weighing 90-434 kg. METHODS A ventral median celiotomy was used to access the left or right kidney. To facilitate surgical exposure, the small intestine was reflected towards the diaphragm using laparotomy sponges and the ascending colon was exteriorized and in some cases evacuated. The peritoneum over the affected kidney was incised and blunt dissection used to free the kidney from the retroperitoneal fat, then the renal artery, vein, and ureter were isolated and ligated. Abdominal lavage with sterile saline solution was performed before abdominal closure. RESULTS Four horses, 1 donkey, and 1 mule had unilateral nephrectomy to treat verminous nephritis (1), idiopathic hematuria (1), and ectopic ureter (4). A ventral median approach provided adequate access to the kidney in all 6 cases. Two horses had postoperative complications (peritonitis, chylous abdominal effusion) that resolved with medical therapy. No complications attributable to nephrectomy were reported by the owners upon follow-up 1-8 years after surgery. CONCLUSIONS A ventral median approach for nephrectomy can be used for unilateral nephrectomy in equids weighing up to 434 kg.

Lungworms in donkeys: Evaluation of Anthelmintics Under Field Conditions

Summary In a herd of large donkeys, 30 (86%) were lungworm positive by the Baermann fecal technique. Eleven donkeys treated with fenbendazole (50 mg/kg) and 11 donkeys treated with thiabendazole were still lungworm positive 2-weeks posttreatment (PT). Subsequent treatment of 21 donkeys with ivermectin resulted in negative lungworm evaluations 2-weeks PT. At 20 weeks PT, all 8 donkeys evaluated were negative, while 7 of 12 donkeys evaluated were lungworm negative at 35-40 weeks PT. Five donkeys, given oral ivermectin paste at 6-8 month intervals after the 20-week evaluation were lungworm negative 4-5 years later.