Abstract: Objective The goal of this work is to study the dark adaptation curve of the normal horse electroretinogram (ERG). Procedures The electroretinographic responses were recorded from six healthy female ponies using a contact lens electrode and a mini-Ganzfeld electroretinographic unit. The horses were sedated intravenously with detomidine, an auriculopalpebral nerve block was then performed, and the pupil was fully dilated. The ERG was recorded in response to a low intensity light stimulus (30 mcd.s/m2) that was given at times (T) T = 5, 10, 15, 20, 25, 30, 40, 50, and 60 min of dark adaptation. Off-line analysis of the ERG was then performed. Results Mean b-wave amplitude of the full-field ERG increased continuously from 5 to 25 min of dark adaptation. The b-wave amplitude peaked at T = 25, however, there was no statistical significance between T = 20 and T = 25. The b-wave amplitude then remained elevated with no significant changes until the end of the study at T = 60 (P > 0.49). The b-wave implicit time increased continuously between T = 5 and T = 20, then gradually decreased until T = 60. No distinct a-wave was observed during the testing time. Conclusions Evaluation of horse rod function or combined rod/cone function by means of full-field ERG should be performed after a minimum 20 min of dark adaptation.

Abstract: A female American saddlebred horse was presented for surgical correction of a possible pseudohermaphrodite condition. The horse had abnormal external genitalia and exhibited stallion-like behaviour. No evidence of uterine or ovarian tissue was identified on laparoscopic examination, but hypoplastic testicular-like tissue was removed, although this was found to contain no spermatogonia upon histopathological examination. A karyotype was performed and showed the normal chromosomal complement for a female horse (64,XX). Polymerase chain reaction to detect the SRY gene was negative in peripheral blood as well as the testicular-like tissue. This case represents the first report of an SRY negative XX-male sex reversal intersex phenotype, which is a potentially inherited condition, in an American saddlebred horse.

Abstract: Abstract Only few quantitative reports exist about the concentrations and induction of immunoglobulin A (IgA) in mucosal secretions of horses. Despite this, it is widely assumed that IgA is the predominant immunoglobulin on mucosal surfaces in the horse. Here, two new monoclonal antibodies (mAbs) against equine IgA, clones 84-1 and 161-1, were developed and characterized in detail. Both IgA mAbs specifically bound monomeric and dimeric equine IgA in different applications, such as Western blots and fluorescent bead-based assays. Cross-reactivity with other equine immunoglobulin isotypes was not observed. The new IgA mAb 84-1 was used in combination with the previously characterized anti-equine IgA mAb BVS2 for the development and validation of a fluorescent bead-based assay to quantify total IgA in equine serum and various secretions. The IgA assay's linear detection ranged from 64 pg/ml to 1000 ng/ml. For the quantification of IgA in serum or in secretions an IgA standard was purified from serum or nasal wash fluid (secretory IgA), respectively. The different standards were needed for accurate IgA quantification in the respective samples taking the different signal intensities of monomeric and dimeric IgA on the florescent bead-based assay into account. IgA was quantified by the bead-based assay established here in different equine samples of healthy adult individuals. In serum the median total IgA was 0.45 mg/ml for Thoroughbred horses (TB, n = 10) and 1.16 mg/ml in Icelandic horses (ICH, n = 12). In nasopharyngeal secretions of TB (n = 7) 0.13 mg/ml median total IgA was measured, and 0.25 mg/ml for ICH (n = 12). Saliva of ICH (n = 6) contained a median of 0.15 mg/ml, colostrum of Warmbloods (n = 8) a median of 1.89 mg/ml IgA. Compared to IgG1 and IgG4/7 quantified in the same samples, IgA appeared as the major immunoglobulin isotype in nasopharyngeal secretions and saliva while it is a minor isotype in serum and colostrum. The newly developed monoclonal antibodies against equine IgA and the resulting bead-based assay for quantification of total IgA can notably improve the evaluation of mucosal immunity in horses.

Abstract: OBJECTIVE: To assess the effects of a single intravenous dose of butorphanol (0.1 mg kg(-1)) on the nociceptive withdrawal reflex (NWR) using threshold, suprathreshold and repeated subthreshold electrical stimuli in conscious horses. STUDY DESIGN: 'Unblinded', prospective experimental study. ANIMALS: Ten adult horses, five geldings and five mares, mean body mass 517 kg (range 487-569 kg). METHODS: The NWR was elicited using single transcutaneous electrical stimulation of the palmar digital nerve. Repeated stimulations were applied to evoke temporal summation. Surface electromyography was performed to record and quantify the responses of the common digital extensor muscle to stimulation and behavioural reactions were scored. Before butorphanol administration and at fixed time points up to 2 hours after injection, baseline threshold intensities for NWR and temporal summation were defined and single suprathreshold stimulations applied. Friedman repeated-measures analysis of variance on ranks and Wilcoxon signed-rank test were used with the Student-Newman-Keul's method applied post-hoc. The level of significance (alpha) was set at 0.05. RESULTS: Butorphanol did not modify either the thresholds for NWR and temporal summation or the reaction scores, but the difference between suprathreshold and threshold reflex amplitudes was reduced when single stimulation was applied. Upon repeated stimulation after butorphanol administration, a significant decrease in the relative amplitude was calculated for both the 30-80 and the 80-200 millisecond intervals after each stimulus, and for the whole post-stimulation interval in the right thoracic limb. In the left thoracic limb a decrease in the relative amplitude was found only in the 30-80 millisecond epoch. CONCLUSION: Butorphanol at 0.1 mg kg(-1) has no direct action on spinal Adelta nociceptive activity but may have some supraspinal effects that reduce the gain of the nociceptive system. CLINICAL RELEVANCE: Butorphanol has minimal effect on sharp immediate Adelta-mediated pain but may alter spinal processing and decrease the delayed sensations of pain.

Abstract: Recent studies suggest that populations and species often exhibit behavioral syndromes; that is, suites of correlated behaviors across situations. An example is an aggression syndrome where some individuals are more aggressive, whereas others are less aggressive across a range of situations and contexts. The existence of behavioral syndromes focuses the attention of behavioral ecologists on limited (less than optimal) behavioral plasticity and behavioral carryovers across situations, rather than on optimal plasticity in each isolated situation. Behavioral syndromes can explain behaviors that appear strikingly non-adaptive in an isolated context (e.g. inappropriately high activity when predators are present, or excessive sexual cannibalism). Behavioral syndromes can also help to explain the maintenance of individual variation in behavioral types, a phenomenon that is ubiquitous, but often ignored. Recent studies suggest that the behavioral type of an individual, population or species can have important ecological and evolutionary implications, including major effects on species distributions, on the relative tendencies of species to be invasive or to respond well to environmental change, and on speciation rates. Although most studies of behavioral syndromes to date have focused on a few organisms, mainly in the laboratory, further work on other species, particularly in the field, should yield numerous new insights.