Effect of Follicle Size and Follicle-Stimulating Hormone on Ovulation Induction and Embryo Recovery in the Mare

The timing of ovulation is an important component to many equine breeding strategies. The action of luteinizing hormone on ovulation induction has been recognized; however, potential effects of follicle-stimulating hormone (FSH) have been less defined. Objectives of this study were to determine whether (1) mares could be induced to ovulate follicles ≤30 mm; (2) equine FSH (eFSH) has a positive effect on ovulation induction, and (3) ovulation of small follicles would affect embryo recovery. Light-horse mares (n = 12) between 4 and 10 years of age were assigned to treatments when they had a dominant growing follicle with a mean diameter of 24, 28, or 35 ± 2 mm and endometrial edema. Treatments were (1) H35, human chorionic gonadotropin (hCG) at 35 ± 2 mm; (2) F35, eFSH at 35 ± 2 mm; (3) H28, hCG at 28 ± 2 mm; (4) FH28, eFSH and hCG at 28 ± 2 mm; (5) D28, deslorelin (gonadotropin-releasing hormone [GnRH] analog) at 28 ± 2 mm; (6) FH24/H24, hCG or eFSH and hCG at 24 ± 2 mm. Mares’ reproductive tracts were scanned at 24 ± 2-hour intervals after treatment to detect ovulation. Mares were inseminated, and embryos were collected. Numbers of mares that ovulated within 48 ± 2 hours after treatment were: H35, 8/8 (100%); F35, 8/14 (57%); H28, 7/12 (58%); FH28, 9/12 (75%); D28, 3/7 (43%) and FH/H24, 4/14 (29%). The number of mares that ovulated in 48 ± 2 hours for H35 was not different from that for FH28 but was higher (P < .05) than all other groups. Embryo recovery rates, diameters, developmental stages, and morphology scores were not different for mares ovulating 48 hours or less versus more than 48 hours after treatment or among treatment groups. Results of this study demonstrate that follicles ≤30 mm can be induced to ovulate with no effect on embryo recovery or quality, as assessed by stereomicroscopy.     

How Do Horses Appraise Humans' Actions? A Brief Note over a Practical Way to Assess Stimulus Perception

Heart rate (HR) is considered to be an effective tool for assessing animals' emotional response to a stimulus. We investigated changes in HR during a series of handling procedures (grooming test) in horses that had different experiences of human interaction. We used four groups of horses: grazing horses (group A), school horses (group B), six ponies, traditionally trained (group C), and six ponies, trained with modulated stimulus intensity (group D). An HR monitor was applied to each horse. The operator began the grooming test, standardized at the following points: (1) trainer's entry into the enclosure/paddock, (2) halter fastened, (3) start of grooming, (4) end of grooming, (5) saddling, and (6) inserting the bit. Group A repeated the grooming test twice: group A1 with a known operator and group A2 with an unknown operator. The data were compared by using analysis of variance (ANOVA) tests. The results showed a significant increase in HR (P ≤ .05) at point 2 compared with baseline in all groups except group D. Other significant differences were found at all points between groups A1 and A2, groups A2 and B, groups A1 and C, groups B and C, and at points 5 and 6 between groups A2 and C, as well as between groups C and D. Even when a scientific assessment of the increase in the HR is of primary importance, the use of this physiologic parameter may be helpful in assessing the horse's perceptions of stimuli presented by people during handling. Our results show that it is not the action “per se” that is important, but the manner in which horses perceive and appraise such actions in relation to the environment and their subject's experiences.     

Status of Lipid Peroxidation, Antioxidants, and Oxidation Products of Nitric Oxide in Equine Babesiosis: Status of Antioxidant and Oxidant in Equine Babesiosis

Equine babesiosis is a tick-borne protozoal disease of horses caused by Theileria equi and Babesia caballi. The disease is endemic in most tropical and subtropical areas. The aim of this paper is to assess the antioxidant status, lipid peroxidation, and oxidation products of nitric oxide (NO) in horses and mules naturally infected with T. equi and B. caballi. East and Southeast Anatolian horses and mules living in rural region of the Eastern border of Turkey were used as the material for this study. These animals are used as pack animal (3–7 years of age). Infected animals were in acute or subacute infection period. In the current study, malondialdehyde (MDA), oxidation products of NO (nitrate and nitrite), serum glutathione (GSH), vitamin E, and retinol levels were analyzed in 58 equids (horse and mule) infected with T. equi and B. caballi as well as in 44 healthy equids. Compared with controls, the level of MDA and nitrate increased significantly (P < .01, P < .05, respectively), whereas GSH concentration and levels of vitamin E decreased significantly (P < .01). There was no significant change in the level of nitrite and retinol between two groups. The results of the current study suggest that in equids infected with T. equi and B. caballi, this alteration in the lipid peroxidation, oxidants, and antioxidants may be related to the host's defenses against parasitic infection and may play a central role in the pathologic conditions associated with babesiosis.     

Systemic Proteoglycan Deposition Is Not a Characteristic of Equine Degenerative Suspensory Ligament Desmitis (DSLD)

Recently Degenerative Suspensory Ligament Desmitis (DSLD) has been proposed to be a disease characterized by systemic deposition of proteoglycan (PG) in connective tissues. To investigate this hypothesis, 6 clinically affected Peruvian Paso horses were compared to 2 unaffected quarterhorses and one unaffected standardbred. Histological sections of limb ligaments and tendons, nuchal ligaments, aortas, hearts, eyes, visceral organs and brains from both groups were stained with H&E as well as special stains for PG. Safranin-O stained sections were found to be optimal for elucidating the presence of PG. Although lesions characteristic of DSLD were present in suspensory ligaments of each clinically affected horse, including foci of chondroid metaplasia with abundant PG, a similar but less pronounced pattern of PG deposition was present in control horses. In contrast to findings of the previous study, PG deposition was not unique to DSLD horses, and PG deposition in aortas and nuchal ligaments of some control horses exceeded levels of PG present in similar tissue of DSLD horses. Furthermore, the “vascular lesion” described in the media of arteries as cellular separation and intercellular amorphous matrix deposition was within the spectrum of changes recognized in both affected and unaffected horses. We found no evidence that DSLD is a systemic PG deposition disease.     

A Comparison of Daily Rhythm of Creatinine and Creatine Kinase in the Sedentary and Athlete Horse

The goal of this study was to investigate the existence of a daily rhythm of creatinine or creatine kinase (CK) and the influence of physical exercise on these rhythms. Blood samples from 20 Sella Italiana horses were collected every 4 hours for 48 consecutive hours via an intravenous cannula inserted into the jugular vein. The horses were divided into two equal groups (Sedentary [S] and Athlete [A]). After 2 weeks of rest, athletes (AR) were subjected again to sample collection every 4 hours for 48 consecutive hours, and sera creatinine and CK were assessed. Statistical analysis of the data was performed by one-way repeated analysis of variance (ANOVA), paired Student's t-test, unpaired Student's t-test, and analysis of single cosinor method. Cosinor analysis identified the periodic parameters and their acrophases (expressed in hours) during the 2 days of monitoring. In all horses, we found a highly significant effect of time of the day on the studied parameters (P < .01). Statistically significant differences were observed for mean serum CK values between sedentary and athlete horses. The application of the periodic model showed a daily rhythm of the parameters studied in all experimental conditions. The results obtained during the experimental period indicated a daily rhythm of creatinine and CK in sedentary and athlete horses and also indicated that physical exercise was able to influence amplitude, acrophase, and robustness of the creatinine and CK circadian rhythm.     

Effects of Density and Rest Stops on Movement Rates of Unrestrained Horses during Transport

The goal of this study was to provide estimates of how much loose (unrestrained) horses move during transport. Data were collected from six shipments of slaughter horses that were transported in a 16.2-m, single-deck semi-trailer in June and July of 2004 for 18 to 20 hours as part of an earlier project. Usable video was obtained from five groups of mature horses transported at “low” density (five to seven horses per group averaging 216.5 kg/m²) and three groups of horses transported at “moderate” density (10–11 horses per group averaging 345.5 kg/m²). Three low-density and two moderate-density groups had access to six water bowls inserted through the sides of the compartments during 1-hour rest stops occurring after 8 hours and at the end of transport. Twelve cameras, one mounted in each corner of the three compartments, were used to record behavior. Distance and rate of movement by individual horses during transport and during two 1-hour rest periods were determined by analysis of 206 hours of usable video footage of individual horses. Mean movement rate tended to be higher during travel (4.23 m/hour) than during the 1-hour periods when the truck was stopped (2.75 m/hour), but it did not seem to be influenced by group density. Movement was stimulated by the availability of water during the rest stops. In general, movement was strongly influenced by one or two horses causing disruption of the group, and not by independent actions of members of the group.     

Determination of the minimum alveolar concentration of isoflurane in Shetland ponies using constant current or constant voltage electrical stimulation

Objective To determine the minimum alveolar concentration (MAC) of isoflurane in Shetland ponies using a sequence of three different supramaximal noxious stimulations at each tested concentration of isoflurane rather than a single stimulation. Study design Prospective, experimental trial. Animals Seven 4‐year‐old, gelding Shetland ponies. Methods The MAC of isoflurane was determined for each pony. Three different modes of electrical stimulation were applied consecutively (2 minute intervals): two using constant voltage (90 V) on the gingiva via needle‐ (CVneedle) or surface‐electrodes (CVsurface) and one using constant current (CC; 40 mA) via surface electrodes applied to the skin over the digital nerve. The ability to clearly interpret the responses as positive, the latency of the evoked responses and the inter‐electrode resistance were recorded for each stimulus. Results Individual isoflurane MAC (%) values ranged from 0.60 to 1.17 with a mean (±SD) of 0.97 (±0.17). The responses were more clearly interpreted with CC, but did not reach statistical significance. The CVsurface mode produced responses with a longer delay. The CVneedle mode was accompanied by variable inter‐electrode resistances resulting in uncontrolled stimulus intensity. At 0.9 MAC, the third stimulation induced more positive responses than the first stimulation, independent of the mode of stimulation used. Conclusions The MAC of isoflurane in the Shetland ponies was lower than expected with considerable variability among individuals. Constant current surface electrode stimulations were the most repeatable. A summation over the sequence of three supramaximal stimulations was observed around 0.9 MAC. Clinical relevance The possibility that Shetland ponies require less isoflurane than horses needs further investigation. Constant current surface‐electrode stimulations were the most repeatable. Repetitive supramaximal stimuli may have evoked movements at isoflurane concentrations that provide immobility when single supramaximal stimulation was applied.