K.L. Waite

Computed tomography as a method of estimating bone mineral content in horses

Summary With the advancement of technology, more tools and methods are being made available for the assessment of bone density in the live animal. Computed tomography (CT) is one such tool. In a CT scan, x-rays are passed through a subject and detectors record transmitted energy. The CT computer then constructs cross-sectional images from this data to represent the internal anatomy. The first objective of this study was to investigate CT as a means of estimating bone mineral content of the equine third metacarpal bone. Our hypothesis was that the cross-sectional area of the third metacarpal bone, as measured on CT images, would correlate significantly with ash weight of that section. Our second objective was to use CT to measure and compare bone density in the dorsal, palmar, lateral and medial cortices of the equine third metacarpus. We hypothesized that CT would detect differences in density by cortex. Twelve cadaver thoracic limb specimens, from horses of varying age, breed and prior use, were scanned on a CT 9800 (GE Medical Systems). Scanned sections of the limb were then skinned, dried, ether-extracted and ashed in a muffle furnace. Bone mineral content was expressed as grams of ash/cm section of bone. The image recorded by the CT was developed and assessed using an imaging photodensitometer and a corresponding software package to estimate the area of each bone section. Correlation was determined using SAS (6.12). Differences in bone density by cortex were calculated using a simple t-test. The maximum, minimum and mean estimates of third metacarpal bone cross-sectional area as determined by CT were 519, 351 and 423 mm 2 , respectively, while the maximum, minimum and mean ash weights were 8.9, 4.8 and 6.4 g/cm, respectively. Estimates of bone mineral content by ash and cross-sectional area as determined by CT were significantly correlated (r=.91, P=.0001). There was no difference in CT density numbers between lateral and medial cortices, however the dorsal cortex was lower in density than the lateral (P

Increased plasma silicon concentrations and altered bone resorption in response to sodium zeolite a supplementation in yearling horses

Abstract This study examined the effect of supplementation of a bioavailable source of silicon (sodium zeolite A) on altering systemic markers of bone metabolism in horses. Twenty yearlings (ten Quarter Horses and ten Arabians) were randomly grouped as silicon (Si) supplemented (S; n=10), in which yearlings consumed 2% of the total diet as a Si-containing supplement, and a second non-supplemented control group (C; n=10). Blood samples were taken on days 0, 15, 30 and 45. Both plasma and serum were collected; the plasma was analyzed for Si concentrations and serum was analyzed for osteocalcin (OC), carboxy-terminal pyridinoline cross-linked telopeptide region of type I collagen (ICTP), and pyridinoline and deoxypyridinoline crosslinks (PYD). Supplemented yearlings had higher plasma Si concentrations than C yearlings by day 15, and remained higher than C yearlings on days 30 and 45 (P .05); however, ICTP concentrations were lower in S yearlings on day 45 when compared to C yearlings (P = .04). Results indicate that sodium zeolite A supplementation (consumed at 2% of the total diet) increases plasma Si concentrations. Furthermore, results indicate that Si-supplemented yearlings may have decreased bone resorption, which may provide for greater net bone formations, as OC concentrations were not different between groups. Unfortunately, systemic markers give no indication as to the quality of the bone that may be formed, and further research in the area of Si supplementation, bone metabolism and bone strength is required to establish conclusive evidence as to the benefits of supplemental Si to the skeletal system.

Quantifying aggressive riding behavior of youth barrel racers and conflict behaviors of their horses

ABSTRACT Research shows that thoroughbred race horses reach top velocity when no whip is used and that increased whip use is not related to variation in velocity or improved finish position. The cloverleaf barrel race is a popular timed event among American youth riders, who are often encouraged to aggressively use both the whip and leg to increase the velocity of the horse. Hence, the purpose of this study was to quantify aggressive riding behaviors among youth riders in a timed cloverleaf barrel race, as well as specific horse behaviors. The first hypothesis stated there is a positive correlation between aggressive rider behaviors and performance time, such that increased aggressive riding would result in increased, and hence slower, run times. The second hypothesis asserted a positive correlation exists between aggressive rider behaviors and horse behaviors. Study participants included 64 horse‐and‐rider teams competing in a state‐level cloverleaf barrel race. This class was chosen because it allows for recording of individual runs of horse‐and‐rider pairs. Patterns were of the same measured distance, in the same arena, with the same footing conditions. Each horse‐and‐rider combination was videotaped from the time they approached the gate to the time they dismounted after their run. Three trained observers separately assessed horse and rider behaviors, and frequency of behaviors was recorded using a predetermined ethogram. Interobserver reliability of trained personnel ranged from 0.69 to 0.97. Aggressive riding did not enhance competition time (mean equaled 19.33 ± 1.77 seconds). There was a small but significant positive relationship between mean gate and whip scores (r = 0.25; P < 0.05): horses whipped more during the run were more likely to react poorly to entering the arena. Similarly, there was a small but significant correlation between mean kick and pop‐up scores (r = 0.30; P < 0.05): horses kicked more frequently by the rider were more likely to perform small rears. Finally, mean tail lashing and pop‐up score were significantly correlated (r = 0.36; P < 0.005). These data suggest that rider behavior does influence horse behavior in cloverleaf barrel racing and provide supporting evidence for future youth education programs.