Effect of surgical technique for unilateral orchiectomy on subsequent testicular function in Miniature Horse stallions.

REASONS FOR PERFORMING STUDY: Management decisions on unilateral orchiectomy are often influenced by the potential for post operative return to successful breeding. The effects of 2 surgical methods (first intention [FI] vs. second intention [SI] incision healing) for unilateral orchiectomy on resulting semen quality and scrotal temperature were evaluated. OBJECTIVE: To evaluate the effects of 2 surgical unilateral orchiectomy techniques on scrotal healing, size of the remaining testis and post operative sperm quality. MATERIALS AND METHODS: Unilateral orchiectomy was performed on mature Miniature Horse stallions. Semen was collected prior to and up to 60 days after, unilateral orchiectomy. Semen parameters, scrotal and body temperatures, testis volume and days to incision healing were evaluated. RESULTS: There was no effect of treatment or time on percent total sperm motility. Total sperm numbers were higher (P < 0.05) 60 days after unilateral orchiectomy compared with 14 and 30 days. Percent viable sperm were higher (P < 0.05) 30 and 60 days compared with pre- and 14 day post unilateral orchiectomy. Scrotal temperatures were lower after unilateral orchiectomy compared with preoperative values ( < or = 0.003). Higher scrotal temperatures were recorded in Group IF, as compared with Group IS, during recoveryfrom anaesthesia and at 1 and 2 h after surgery (P = 0.02). Mean time to incision healing was less in Group II (10.0 days) than in Group II (21.5 days; P = 0.05). CONCLUSION: In this study, total sperm motility was maintained and size of the remaining testis, total sperm numbers and percent viable sperm increased after unilateral orchiectomy. Incision healing time was shorter in Group II; however, surgical technique did not have an effect on semen quality at 30 and 60 days post unilateral orchiectomy. POTENTIAL RELEVANCE: These data suggest that surgical technique for unilateral orchiectomy may not dramatically influence function of the remaining testis.

Comparison of primary closure of incisional hernias in horses with and without the use of prosthetic mesh support.

REASONS FOR PERFORMING STUDY: Repair of incisional hernias in horses has been described previously; however, this report describes the outcome of primary closure of incisional hernias in a large number of horses and compares these results with those of mesh implantation. OBJECTIVE: To report the perioperative care, complications and long-term outcome of primary closure of incisional hernias in horses and to compare these results with a second population of horses in which prosthetic mesh was used. METHODS: Medical records of horses undergoing an incisional herniorrhaphy between 1998 and 2009 were reviewed. Information obtained included case details, factors from the initial surgery that contributed to the hernia formation, method of hernia repair and outcome. Comparisons between horses with and without mesh were made using logistic regression. RESULTS: Thirty-eight horses with primary closure and 9 horses with mesh implantation met inclusion criteria. Long-term follow-up for cases in which a mesh was not used was available for 25 cases; of these, 21 horses (84%) had a normal cosmetic appearance and 4 (16%) had a visible defect. There was no significant difference between the 2 repair methods in terms of age, sex, breed, weight, size of the hernia, number of defects, timing of the repair or cosmetic outcome. Horses in which a mesh was used had significantly longer duration of surgery and hospitalisation, and were significantly more likely to develop post operative complications while having a longer duration of convalescence prior to return to use. CONCLUSIONS: Primary apposition of incisional hernias in horses without the use of mesh support appears to result in a good cosmetic outcome while avoiding the complications associated with mesh implantation in this population of horses. POTENTIAL RELEVANCE: Surgical time, duration of hospitalisation, and post operative complications may be reduced by using this technique of primary repair and avoiding mesh implantation.

Risk factors associated with development of postoperative ileus in horses.

OBJECTIVE: To determine risk factors associated with development of postoperative ileus in horses undergoing surgery for colic. DESIGN: Case-control study. ANIMALS: 69 horses that developed ileus after surgery for colic and 307 horses that did not develop postoperative ileus. PROCEDURE: Signalment, history, clinicopathologic data, treatment, lesions, and outcome were obtained from medical records. RESULTS: Variables associated with increased risk of postoperative ileus included age > 10 years, Arabian breed, PCV > or = 45%, high serum concentrations of protein and albumin, anesthesia > 2.5 hours' duration, surgery > 2 hours' duration, resection and anastomosis, and lesions in the small intestine. Enterotomy reduced the risk of postoperative ileus. After multivariate logistic regression, the final model included the variables Arabian breed, PCV > or = 45%, lesion type, duration of surgery (> 2 hours vs < or = 2 hours), and pelvic flexure enterotomy. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that by evaluating certain factors, horses at increased risk of postoperative ileus may be recognized before the condition develops. Preventative treatment and early intervention may be instituted in these horses. Shortening surgery time and performing an enterotomy may decrease the probability of horses developing postoperative ileus.

Risk factors for enterolithiasis among horses in Texas.

OBJECTIVE: To identify risk factors for enterolithiasis in horses. DESIGN: Matched case-control study. ANIMALS: 26 horses with enteroliths, 104 horses with other causes of colic that underwent surgery (52 horses, surgical control group) or were treated medically (52 horses, nonsurgical control group). PROCEDURE: Medical records were reviewed for horses with enteroliths and control horses. Information collected included signalment, anamnesis, and findings on physical examination and clinicopathologic testing at admission. Horses with enteroliths and control horses were compared by means of conditional logistic regression to identify factors associated with enterolithiasis. RESULTS: Horses that were fed alfalfa hay, spent < or = 50% of time outdoors, or were Arabian or miniature breeds had an increased risk of developing enteroliths. Horses with enteroliths were more likely to have been hyperbilirubinemic and to have had clinical signs > 12 hours prior to admission. CONCLUSIONS AND CLINICAL RELEVANCE: Breed and diet appear to influence the risk of enterolithiasis; other management factors also may influence development of enteroliths. Duration of clinical signs may be longer and signs may be less severe among horses with enteroliths, compared with horses with other causes of colic.

Intracellular microelectrode recording to characterize inhibitory neuromuscular transmission in jejunum of horses.

OBJECTIVE: To evaluate electrical activity of jejunal circular muscle in horses and characterize electrical responses to stimulation by intrinsic inhibitory neurons. SAMPLE POPULATION: Portions of jejunum obtained from horses euthanatized for reasons other than gastrointestinal tract disease. PROCEDURE: Isolated circular muscle preparations were perfused with oxygenated modified Krebs solution. Glass microelectrodes were used for intracellular recording of membrane potentials from single smooth muscle cells. Electrical activity and responses to electrical field stimulation (EFS) of intrinsic neurons in the presence of guanethidine and atropine were recorded. Mediators of responses to nerve stimulation were also evaluated, using N-nitro-L-arginine methyl ester (L-NAME) and apamin. RESULTS: Mean resting membrane potential (RMP) was 41.5+/-1.8 mV. Small membrane potential oscillations were observed in muscle cells. Single or multiple action potentials were often superimposed on the peaks of these oscillations. Spontaneous oscillations and action potentials were blocked by nifedipine. Transient hyperpolarizations of smooth muscle cell membrane potentials (inhibitory junction potentials [IJP]) were observed in response to electrical field stimulation. The IJP evoked by stimulus trains consisted of an initial fast component followed by a slow component. The L-NAME did not have a significant effect on RMP and did not significantly affect the fast component of IJP at any stimulus frequency tested. In contrast, L-NAME abolished the slow component of IJP observed after trains of pulses. In the continued presence of L-NAME, apamin had no significant effect on RMP but effectively reduced the fast component of IJP. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggest that inhibitory neurotransmitters supplying equine jejunum act through different ionic mechanisms. Understanding these mechanisms may suggest new therapeutic targets for treatment of motility disorders.

In vitro effects of erythromycin, lidocaine, and metoclopramide on smooth muscle from the pyloric antrum, proximal portion of the duodenum, and middle portion of the jejunum of horses.

OBJECTIVE: To evaluate effects of erythromycin, lidocaine, and metoclopramide on smooth muscle of the pyloric antrum (PA), proximal portion of the duodenum (PD), and middle portion of the jejunum (MJ) of horses. Sample Population-Strips of smooth muscle from 7 horses. PROCEDURE: Isolated muscle strips were suspended in a bath and attached to isometric force transducers. Once stable spontaneous contractions were observed, agents were added. Isometric stress responses were compared with the amplitude of spontaneous contractions. RESULTS: A single dose of erythromycin to the PA increased contractile amplitude (CA) for the longitudinal smooth muscle (mean +/- SEM, 76+/-16 g/cm2) but decreased CA for circular smooth muscle (-79+/-23 g/cm2). The inhibitory effect was decreased by tetrodotoxin, N(G)-nitro-L-arginine methyl ester, and a vasoactive intestinal peptide antagonist. Erythromycin increased CA for the MJ, which was maximal at 10(-4)M (171+/-36 g/cm2). Lidocaine increased CA for the PD, which was maximal at 10(-4) M (60+/-5 g/cm2). Metoclopramide increased the CA, which was maximal at 10(-4) M for the PA (75+/-26 g/cm2), PD (279+/-33 g/cm2), and MJ (456+/-59 g/cm2). CONCLUSIONS: Regional differences in responses to erythromycin, lidocaine, and metoclopramide were evident in the gastrointestinal tract of horses. Metoclopramide increased CA in all tissues used, whereas erythromycin inhibited CA in circular smooth muscle but stimulated CA in longitudinal smooth muscle from the PA. Inhibition is caused by stimulation of inhibitory nerves and is mediated, in part, by nitric oxide and vasoactive intestinal peptide.

Comparison of nuclear scintigraphy and acetaminophen absorption as a means of studying gastric emptying in horses.

OBJECTIVE: To evaluate the correlation between halftime of liquid-phase gastric emptying (T50), determined with nuclear scintigraphy using technetium Tc 99m pentetate, and absorption variables of orally administered acetaminophen. ANIMALS: 6 mature horses. PROCEDURE: Technetium Tc 99m pentetate (10 mCi) and acetaminophen (20 mg/kg of body weight) were administered simultaneously in 200 ml of water. Serial left and right lateral images of the stomach region were obtained with a gamma camera, and T50 determined separately for counts obtained from the left side, the right side and the geometric mean. Power exponential curves were used for estimation of T50 and modified R2 values for estimation of goodness of fit of the data. Serial serum samples were taken, and acetaminophen concentration was determined, using fluorescence polarization immunoassay. Maximum serum concentration (Cmax), time to reach maximum serum concentration (Tmax), area under the curve for 240 minutes and the absorption constant (Ka) were determined, using a parameter estimation program. Correlations were calculated, using the Spearman rank correlation coefficient. RESULTS: Correlations between T50 and Tmax and between T50 and Ka were significant. CONCLUSIONS AND CLINICAL RELEVANCE: Tmax and Ka are valuable variables in the assessment of liquid-phase gastric emptying using acetaminophen absorption. Acetaminophen absorption may be a valuable alternative to nuclear scintigraphy in the determination of gastric emptying rates in equine patients with normally functioning small intestine.

Evaluation of nitric oxide as an inhibitory neurotransmitter in the equine ventral colon.

OBJECTIVE: To determine the role of nitric oxide and an apamin-sensitive nonadrenergic noncholingeric inhibitory transmitter on contractility of the ventral colon of horses. SAMPLE POPULATION: Strips of the circular and longitudinal muscle layers and taenia of the ventral colon from 14 horses. PROCEDURE: Muscle strips were suspended in tissue baths and attached to force transducers. Contractile activity of circular, longitudinal, and taenia muscle strips in response to electrical field stimulation was measured after addition of apamin and a nitric oxide inhibitor, N-nitro-L-arginine methyl ester (L-NAME). RESULTS: Electrical field stimulation reduced contractile activity in the circular muscle layer and taenia but not the longitudinal muscle layer. Addition of L-NAME significantly reduced inhibitory contractile activity at all frequencies for the circular muscle layer, whereas a significant effect was evident for the taenia only at the highest frequency. The combination of L-NAME and apamin resulted in a significant reduction in inhibition of the taenia at all frequencies but for circular muscle only at lower frequencies. CONCLUSIONS AND CLINICAL RELEVANCE: Nitric oxide and an apamin-sensitive neurotransmitter appear to mediate a component of inhibitory transmission in the circular muscle and taenia, but not the longitudinal muscle layer, of the equine ventral colon. Nitric oxide has a role in regulating contractile activity of the equine ventral colon, and nitric oxide synthase inhibitors may be useful in horses with ileus of the large colon.

In vitro effects of nonsteroidal anti-inflammatory agents and prostaglandins I2, E2, and F2alpha on contractility of taenia of the large colon of horses.

OBJECTIVES: To determine the in vitro effect of various prostaglandins (PG) and nonsteroidal anti-inflammatory drugs (NSAID) on contractile activity of the large-colon taenia of horses. ANIMALS: 14 healthy horses. PROCEDURE: The taenia was collected from the ventral colon, cut into strips (2 X 10 mm), and mounted in a tissue bath system (20-ml capacity) that contained oxygenated Krebs buffer solution warmed to 37.5+/-0.5 C. After equilibration, incremental doses of PGE2, PGF2alpha, PGl2, flunixin meglumine, carprofen, ketoprofen, and phenylbutazone were added to the baths, and contractile activity was recorded. Magnitude of the response was calculated by comparing contractile activity before and after administration of the PG or NSAID to the tissue baths. RESULTS: PGE2 and PGF2alpha, caused a significant increase in contractile activity, whereas PGI2 induced an inhibitory response. Activity of NSAID on contraction was predominantly inhibitory. At low concentrations, ketoprofen induced an excitatory effect, which then became inhibitory at high concentrations. Compared with the other NSAID, carprofen significantly reduced contractile activity at lower concentrations. CONCLUSIONS: PGE2 and PGF2alpha appear to enhance contractility of large-colon taenia of horses, whereas PGI2 was inhibitory in the in vitro model. Administration of NSAID also inhibited contractility, with carprofen having the most potent effect. CLINICAL RELEVANCE: Administration of NSAID in combination with liberation of endogenous PG may predispose horses to development of intestinal stasis and subsequent impaction.

Role of nitric oxide in in vitro contractile activity of the third compartment of the stomach in llamas.

OBJECTIVE: To determine the role of nitric oxide and an apamin-sensitive nonadrenergic-noncholinergic inhibitory transmitter in in vitro contractile activity of the third compartment in llamas. SAMPLE POPULATION: Isolated strips of third compartment of the stomach from 5 llamas. PROCEDURE: Strips were mounted in tissue baths containing oxygenated Kreb's buffer solution and connected to a polygraph chart recorder to measure contractile activity. Atropine, guanethidine, and indomethacin were added to tissue baths to inhibit muscarinic receptors, adrenoreceptors, and prostaglandin synthesis. Responses to electrical field stimulation following addition of the nitric oxide antagonist Nwo-nitro-L-arginine methyl ester (L-NAME) and apamin were evaluated. RESULTS: Electrical field stimulation (EFS) resulted in a reduction in the amplitude and frequency of contractile activity, followed by rebound contraction when EFS was stopped. Addition of L-NAME resulted in a significant reduction in inhibition of contractile activity. Addition of apamin also resulted in a significant reduction in inhibitory contractile activity at most stimulation frequencies. The combination of L-NAME and apamin resulted in a significant reduction in inhibition at all frequencies. CONCLUSION: Nitric oxide and a transmitter acting via an apamin-sensitive mechanism appear to be involved in inhibition of contractile activity of the third compartment in llamas. CLINICAL RELEVANCE: Results suggest that nitric oxide plays an important role in mediating contractile activity of the third compartment in llamas. Use of nitric oxide synthase inhibitors may have a role in the therapeutic management of llamas with lesions of the third compartment.

Intra-abdominal testicular torsion in a horse without signs of colic.

A 5-year-old Quarter Horse stallion was admitted for cryptorchidectomy. Abnormalities were not found on physical examination, except for an undescended left testis. Cryptorchidectomy was performed, using an inguinal approach. The tail of the epididymis was in the inguinal canal, and the testis was adjacent to the internal inguinal ring. The testis was dark reddish purple to black, resulting from torsion at the level of the body of the epididymis. On histologic examination, the left testis was necrotic, except for the tunica albuginea and tunica vaginalis visceralis covering the testis. Intra-abdominal testicular torsion developed without signs of abdominal pain and resulted in necrosis of the affected testis. If cryptorchidectomy had not been performed, it is likely that the horse would have been found to be monorchid. Unrecognized intra-abdominal testicular torsion may be the cause of monorchidism in some horses.

Involvement of nitric oxide in inhibitory neuromuscular transmission in equine jejunum.

OBJECTIVES: To evaluate the role of nitric oxide (NO), vasoactive intestinal peptide (VIP), and a transmitter acting through an apamin-sensitive mechanism in mediating inhibitory transmission in the equine jejunal circular muscle, and to determine the distribution of VIP-and NO-producing nerve fibers in the myenteric plexus and circular muscle. PROCEDURE: Circular muscle strips were suspended in tissue baths containing an oxygenated modified Krebs solution and attached to isometric force transducers. Responses to electrical field stimulation (EFS), tetrodotoxin, the NO antagonists L-N-nitro-arginine-methyl-ester (L-NAME) and N-nitro-L-arginine, apamin, VIP, authentic NO, and the NO donar sodium nitroprusside were tested. Immunostaining for VIP-like and NADPH diaphorase histochemical staining were performed on paraformaldehyde fixed tissue. RESULTS: Subpopulations of myenteric neurons and nerve fibers in the circular muscle were positive for NADPH diaphorase and VIP-like staining. EFS caused a frequency-dependent inhibition of contratile activity. Tetrodotoxin prevented the EFS-induced inhibition of contractions. L-NAME (200 microM) and apamin (0.3 microM) significantly (P < 0.01) reduced EFS-stimulated inhibition of contractile activity at most frequencies tested. The effects of L-NAME and apamin were additive. In their combined presence, EFS induced excitation instead of inhibition (196.7% increase at 5 Hz, n = 28, P < 0.01). Inhibition of contractile activity by EFS was mimicked by sodium nitroprusside. Authentic NO (3-6 microM) abolished contractile activity. VIP induced a dose-dependent inhibition of contractile activity (89.1 +/- 6.3% reduction at approximately 0.3 microM, n = 16). Antagonism of NO synthesis did not alter the response to VIP. CONCLUSION: NO, VIP, and a substance acting through an apamin-sensitive mechanism appear to comediate inhibitory transmission in the equine jejunal circular muscle. CLINICAL RELEVANCE: These findings may suggest new therapeutic targets for motility disorders, such as agents that inhibit the synthesis or actions of NO.

Fractures of the humerus.

The treatment of humeral fractures in ruminants remains a challenge to the large animal surgeon. Often the recommendation is to euthanize the animal. This article reviews four different treatment techniques: stall confinement, intramedullary pinning, interlocking nails, and plate fixation. Clinical cases are drawn from both the literature and personal experience to demonstrate the potential application of each treatment modality.

Tube cystostomy for treatment of obstructive urolithiasis in small ruminants.

Tube cystostomy was used to treat 13 goats and two sheep with obstructive urolithiasis. The cystostomy tube was intermittently occluded 3 to 4 days after placement to determine if urine could be voided through the urethra. If the animal showed no discomfort during urination after the cystostomy tube had been occluded for several days, the tube was removed. This procedure was successful in relieving urethral obstruction in 12 animals. The mean time until the animal could urinate freely and until the cystostomy tube was removed was 11.5 and 14.4 days respectively. Follow-up was available for 10 animals; seven were alive with no recurrence of urinary obstruction. One goat died from unrelated to urinary obstruction 1 year postoperatively. One goat died from unknown causes, and one goat died after urinary obstruction recurred.

Surgical repair of atresia jejuni in two calves.

Two Holstein calves with similar histories of not defecating since birth were determined to have atresia jejuni. Resection of the distended blind end of the jejunum and the remaining jejunum and ileum followed by a jejunocecostomy was performed. One calf died 7 months after surgery of unknown causes. The second calf has survived for greater than 1 year, and has maintained a growth rate similar to other calves its age. Atresia jejuni has been reported to be a universally fatal disorder of unknown pathogenesis. It has been postulated that intestinal atresia is caused by palpation of the amniotic vesicle at the time of pregnancy diagnosis, between days 36 and 42 of gestation.

Arytenoid cartilage movement in resting and exercising horses.

Endoscopic examinations of the larynx were recorded on 49 horses at rest and while exercising on a 5% inclined high-speed treadmill for 8 minutes at a maximum speed of 8.5 m/sec. Subjective laryngeal function scores at rest and while exercising were based on the degree and synchrony of arytenoid abduction. Arytenoid abduction was expressed as a left:right ratio of rima glottidis measurements. Horses with arytenoid cartilage asynchrony at rest (grade 2) could not be distinguished from normal horses (grade 1) when exercising because full abduction was maintained throughout the exercise period. Five horses with incomplete left arytenoid abduction at rest (grade 3) maintained full abduction during exercise; one grade 3 horse had dynamic collapse of the left side of the larynx. All horses with laryngeal hemiplegia at rest (grade 4) had dynamic collapse of the left side of the larynx during exercise. Forty-two horses with a resting left:right arytenoid abduction ratio greater than or equal to .71 consistently had complete arytenoid abduction at exercise. Seven horses with a left:right ratio less than .71 consistently showed dynamic collapse at exercise. There was no significant difference in the exercising left:right ratio between normal horses (grade 1) and grade 2 or grade 3 horses. These results suggest that horses with arytenoid asynchrony at rest do not suffer progressive collapse of the rima glottidis during exercise, and that incomplete arytenoid abduction at rest is an unreliable predictor of such collapse. Surgical treatment of all grade 2 horses and some grade 3 horses may be inappropriate.

Cranial approach to the humerus for repair of fractures in horses and cattle.

A cranial approach to the humerus was developed for application of a compression plate for repair of comminuted humeral fractures in a weanling foal, a calf, a heifer, and a mature cow. An incision was made from the cranial portion of the greater tubercle of the humerus to the radius. The cranial aspect of the humerus was exposed by retraction of the brachiocephalicus muscle and blunt dissection between the biceps brachii and brachialis muscles. A second plate was applied laterally in the heifer and cow by retraction of the brachialis muscle and elevation of the extensor carpi radialis muscle. Successful fracture reduction, alignment, and stabilization were achieved in all four animals.

Clinical evaluation of laryngeal sensation in horses.

Sensory innervation of the larynx was examined by tactile stimulation with a blunt biopsy forceps passed through a flexible videoendoscope. Twenty horses with no evidence of laryngeal motor deficit were stimulated on 10 sites by touch with the forceps. Unilateral neurectomies of the internal branch of the left cranial laryngeal nerve were performed on 5 other horses. These horses were stimulated by touch on the same sites preoperatively and up to 1 week postoperatively. In all 25 horses the motor response of the larynx was recorded on videotape and evaluated by 2 observers blind as to treatment and time of evaluation. Normal horses responded to touch by adduction of both arytenoid cartilages, swallowing or both. This response was not altered by sedation with xylazine hydrochloride. Left cranial laryngeal neurectomized horses failed to respond to tactile stimulation of the left side, while adduction of both cartilages, swallowing or both was observed following stimulation on the right side. Laryngeal stimulation by touch with a biopsy forceps was accurate in identifying horses with complete deficits of the internal branch of the cranial laryngeal nerve.