Back problems. Neuroanatomy and neurological examination.

Components of the equine nervous system are described including classical anatomy and newer sensory innervation maps that are useful for localizing lesions to and within the nervous system. The key components in a neurological examination that help differentiate primary neurologic disease from musculoskeletal disorders are explained. Gait deficits associated with neurologic dysfunction are listed as well as diagnostic aids and an overview of differential diagnoses.

Analysis of subfertility associated with homozygosity of the rose comb allele in the male domestic fowl.

Sperm metabolism and duration of fertility were compared between roosters homozygous (RR) and heterozygous (Rr) for the rose comb allele. In the absence or presence of Ca+2, a motility agonist, the metabolic rate of spermatozoa from RR males was 76 to 77% of that of spermatozoa from Rr males. In the presence of caffeine, the metabolic rate of spermatozoa from RR males was increased significantly (P < .05) to 86% of that of spermatozoa from Rr males. Although intramagnal insemination of ejaculated spermatozoa reduced the disparity in duration of fertility between RR and Rr males, the duration of fertility of RR males was still less than that of Rr males. No difference in duration of fertility was observed following intramagnal insemination of testicular spermatozoa. Subfertility associated with RR males seems to stem from an aberrant activation or regulation of spermatozoal metabolism and not a reduction in absolute metabolic capacity per se.

Orotracheal and nasotracheal intubation in llamas.

Orotracheal or nasotracheal intubation was performed in 304 llamas and 6 alpacas during general anesthesia for surgical and diagnostic procedures. The mouth not opening wide and the presence of a prominent torus linguae make orotracheal intubation difficult, but it can be accomplished with the aid of a laryngoscope, using a technique similar to that used in small domestic ruminants. The presence of a pharyngeal diverticulum necessitates modification of nasotracheal intubation techniques to make them applicable for use in llamas and alpacas. When nasotracheal intubation, with phenylephrine lubricant-coated tubes, is not successful, oral laryngoscopy and use of a stylet in the endotracheal tube will improve chances for success. Because llamas are obligate nasal breathers, airway obstruction can develop following removal of endotracheal tubes during recovery from anesthesia. This complication can be prevented by maintaining orotracheal tubes until the animal is able to protect its airway or by using nasotracheal tubes, which allow the llama to stand before the tube has to be removed.

Modulation of the fertilizing ability of spermatozoa from roosters carrying the Sd (sperm degeneration) allele.

Roosters carrying the Sd (sperm degeneration) allele produce spermatozoa that die prematurely in vivo. Consequently, these mutants are subfertile. The objective of the present study was to determine whether or not subfertility could be modulated. A previous study found that the proximal efferent ducts of mutants were characterized by a reduced surface-to-volume ratio. We hypothesized that if subfertility was exacerbated by hemicastration of chicks, which increases daily sperm production in adults, then a relationship between efferent duct function and sperm longevity would be likely. In experiment 1, hemicastration of chicks exacerbated the subfertility of adults (p < 0.001). As inferred from SDS-PAGE in previous research, mutants lack at least one non-albumin seminal plasma protein. Therefore, it was hypothesized that protein supplementation would ameliorate subfertility. In experiment 2, fertility increased (p < 0.001) when spermatozoa from mutants were mixed with albumin-depleted seminal plasma protein from fertile roosters before insemination. In contrast, supplementation with BSA had no effect (p > 0.05). In summary, the subfertile status of Sd roosters was dynamic and appeared to depend upon the interaction of testicular output, efferent duct structure, and seminal plasma protein. Thus the study of this dysfunction may help to identify factors responsible for sperm maturation in the domestic fowl.

Analysis of seminal plasma from roosters carrying the Sd (sperm degeneration) allele.

In previous research, subfertile roosters carrying the Sd (sperm degeneration) allele were characterized by malformed proximal efferent ducts. An abnormal biochemical milieu within the excurrent ducts of the testis was inferred. The objective of the present study was to compare seminal plasma composition between mutant (Sd) and normal (sd+) roosters. Phenotypic mutants were selected--on the basis of sperm viability--from a flock of Delaware roosters. After weekly ejaculations, sperm viability was < 60% for mutant roosters as compared to 100% for normal roosters. As reported previously, sperm viability in mutants increased to normal levels after frequent ejaculation. When comparisons were based on semen containing 100% viable spermatozoa, mutants were comparable to normal roosters with respect to sperm concentration and seminal plasma osmolality. Neither genotype was characterized by seminal plasma proteolytic activity at neutral pH. In contrast, seminal plasma from mutants was characterized by an imbalance of electrolytes, amino acids, and protein. Because the rooster lacks accessory sex glands, seminal plasma composition reflects excurrent duct function. Consequently, the abnormal seminal plasma composition of Sd roosters is attributed to excurrent duct dysfunction.

The fate of Pasteurella multocida after intratracheal inoculation into turkeys.

Young adult turkeys were intratracheally inoculated with the P-1059 strain of Pasteurella multocida, and the fate of the organism was studied by quantifying the organism in various respiratory and systemic tissues at various times after the inoculation. The results showed that, in the first 2 h, on the order of 10(8) to 10(9) organisms deposited at the upper trachea multiplied in situ to gradually spread downwards to the lower respiratory tract. In the majority of turkeys, by 6 h postinoculation the organism invaded the circulatory system and multiplied vigorously in the liver and spleen. In some birds, however, the organism appeared to have reached the liver from the trachea instantaneously by an unidentified mechanism. Vaccination with inactivated vaccines protected turkeys from intratracheal challenge exposure, as well as from intramuscular inoculation.

An improved procedure for intramagnal insemination of the chicken.

Intramagnal insemination is a useful technique in the analysis of spermatozoal function. Precise deposition of spermatozoa requires the use of laparotomy. However, hen-day egg production can be adversely affected by such a procedure. The present work demonstrates that postoperative hen-day egg production is affected by choice of anesthetic. Hens anesthetized with a mixture of ketamine and xylazine prior to laparotomy laid 14% fewer eggs (P less than .05) when compared with intact controls. In contrast, the postoperative hen-day egg production of hens anesthetized with xylazine alone was comparable with that of intact controls (P greater than .05). Furthermore, the use of xylazine alone increased the ease of handling sedated hens and decreased recovery time. Therefore, xylazine is recommended for anesthetizing hens prior to laparotomy.

Analysis of deferent duct morphology in turkeys characterized as low or high semen volume producers.

The objective of the present research was to clarify the basis for the difference in performance of turkey toms characterized as low or high semen volume producers. Variables measured included testicular weight, deferent duct semen volume, and deferent duct morphology based upon plastic casts. Three organizational patterns emerged after viewing plastic casts of deferent ducts: helical, serpentine, and randomly folded coil. THe randomly folded coil was the principal pattern in deferent ducts from low and high semen volume producers alike. No difference in patterns was observed between low and high semen volume producers. Differential semen yield was attributed to a greater testicular mass along with a greater storage capacity of the deferent duct in high semen volume producers. However, deferent duct storage capacity appeared to be the predominant factor affecting semen yield.

Decreased spermatozoal survivability associated with aberrant morphology of the ductuli efferentes proximales of the chicken (Gallus domesticus).

The objective of this research were twofold: 1) to determine if decreased spermatozoal longevity, a previously reported heritable trait in chickens, was attributable to spermatozoal passage through the excurrent ducts, and 2) to document the morphology of the testicular excurrent ducts from affected roosters. Though spermatozoa were viable at ejaculation, as evidenced by their exclusion of ethidium bromide, fertility after intravaginal insemination of spermatozoa from affected roosters was less (p less than 0.001) than that observed with spermatozoa from nonaffected controls, 37 +/- 2.3 versus 58 +/- 1.5%, respectively, over a 21-day egg-collection interval. In contrast, fertility after intramagnal insemination of testicular spermatozoa from affected roosters was equivalent (p greater than 0.05) to that of nonaffected controls, 47 +/- 2.2 versus 41 +/- 3.6%, respectively. After intravaginal insemination, neither type of testicular spermatozoa fertilized oocytes. The ductuli efferentes proximales from affected roosters were characterized by a greater luminal cross-sectional area as well as a diminished height and number of longitudinal epithelial folds (p less than 0.005). It was concluded that heritable decreased spermatozoal longevity in the chicken is not attributable to an inherent spermatozoal defect. Rather, the defect is acquired during passage of spermatozoa through the extragonadal ducts of the rooster.

Dorsal subluxation of the proximal interphalangeal joint in the pelvic limb of three horses.

In horses, dorsal subluxation of the proximal interphalangeal joint in the pelvic limb, which realigned when weight was applied to the limb, improved following surgery. Improvement was observed, if not immediately, at least within two weeks after treatment. The severity and duration of the condition appear to be important considerations in predicting the time necessary for resolution of the condition following surgery. Treatment consisted of surgical resection of a small segment of the medial head of the deep digital flexor tendon in the pelvic limb. The section removed was positioned distal to the tarsus, at the level prior to the tendon joining the main portion of the deep digital flexor tendon. Previously, a surgical treatment was described in which a portion of the accessory ligament (distal check ligament) of the deep digital flexor muscle was resected. Because the medial head is much stronger than the accessory ligament, resection of the tendon of the medial head provides more release of tension to allow stretching of the deep digital flexor muscle tendon.

Decreased sperm survivability in subfertile Delaware roosters as indicated by comparative and competitive fertilization.

Duration of fertility following intravaginal and intramagnal insemination of hens with viable spermatozoa from subfertile Delaware roosters was compared with that obtained with spermatozoa from fertile Leghorns and subfertile Wyandotte roosters. In contrast to results with Leghorn and Wyandotte birds, duration of fertility was not increased following intramagnal insemination of spermatozoa from Delaware birds. Competitive fertilization also demonstrated that duration of fertility was less than expected in the spermatozoa from Delaware birds. Heritable subfertility in Wyandotte and Delaware roosters therefore appears to be attributable to distinct sperm defects.

Alteration of the spermatozoal glycocalyx and its effect on duration of fertility in the fowl (Gallus domesticus).

The hypothesis that sialic acid has a role in spermatozoal sequestration within the hen's oviduct was tested by treating spermatozoa with Clostridium perfringens neuraminidase. Spermatozoal content of sialic acid ranged from 94 to 135 micrograms per 10(9) spermatozoa (n = 12 roosters). Spermatozoa contained 80% of total seminal sialic acid (coefficient of variation = 4.6%). Spermatozoal sialic acid content was reduced by 18% when 10(9) spermatozoa were incubated at pH 6.5 with 10 IU neuraminidase activity (Type V, Sigma Chemical Co.). Such treatment had no effect on spermatozoal viability as evidenced by ethidium bromide uptake. However, treatment of spermatozoa with neuraminidase prior to intravaginal insemination reduced fertility by 24 percentage units (p less than 0.001). In contrast, when similarly treated spermatozoa were deposited in the magnum via laparatomy, fertility was not affected (p greater than 0.05). The preceding work was done with neuraminidase prepared by salt fractionation (Type V, Sigma Chemical Co.). Type V neuraminidase was absorbed to diethylaminoethyl-Sephacel and then eluted with a stepwise KCl gradient. Treatment of spermatozoa with this preparation of neuraminidase (10 IU/10(9) spermatozoa) prior to intravaginal insemination reduced fertility by 19 percentage units (p less than 0.001). Decreased fertility could not be attributed to contamination of neuraminidase preparation with proteolytic activity. We conclude that spermatozoal sialic acid has a role in spermatozoal sequestration within the hen's utero-vaginal glands.

Comparison of sensory nerve conduction velocities in horses versus ponies.

Normal sensory nerve conduction velocity (SNCV) values in 8 ponies and 8 horses were compared by use of a percutaneous signal-averaging technique. Nerve fibers evaluated included those in the medial and lateral palmar and plantar digital nerves. Mean SNCV values were significantly slower (P less than 0.0002) for horses, compared with those values for ponies. Animal height and nerve segment length were inversely related to SNCV consistently. The SNCV values were affected by surface skin temperature by a factor of approximately 1.2 m/s change for 1 degree C change in temperatures from 35 C. The ability to calculate warning limits to define those SNCV values in normal and abnormal ranges were developed from these data for both ponies and horses.

Comparative prenatal development of the spinal cord in normal and dysraphic dogs: embryonic stage.

The prenatal development of the canine spinal cord was examined by light microscopy in 8 normal embryos and compared with the development of the spinal cord in 10 embryos obtained by mating severely dysraphic Weimaraner dogs. Dysraphic lesions were found in 80% of the embryos examined from dysraphic matings. The primary lesion was aberrantly positioned mantle cells ventrad to the central canal in the floor plate area. In 30% of the embryos of this group, there was a division of the terminal neural tube. The dysraphic embryos had significantly shorter gray matter and spinal cord transverse diameters. This confirmed the observation that the mantle cells in the dysraphic specimens were less differentiated, being more compact and appearing more basophilic when hematoxylin and eosin stains were used.

Clinical approach to determine the contribution of the palmar and palmar metacarpal nerves to the innervation of the equine fetlock joint.

To determine the sensory nerve supply of the metacarpophalangeal joint, lameness was induced in eight horses by injecting the joint with a glycerin suspension of glass micropheres. When the medial and lateral palmar nerves were anesthetized in 4 horses, there was noticeable improvement in the gait, but each horse remained lame. When the medial and lateral palmar metacarpal nerves were also anesthetized, 3 of the 4 horses became sound. To confirm the results of local anesthesia, neurectomies were performed on a second group of four horses. The lameness was alleviated only upon resection of both the palmar nerves and the palmar metacarpal nerves.