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in Journal of the American Veterinary Medical Association

The Jockey Club of North America requires that all breeding of Thoroughbred racehorses be limited to live matings. Given this restriction, the traditional number of mares bred by a Thoroughbred stallion during a single 5-month breeding season (referred to as a stallion's book) that will enable a stallion to achieve a target pregnancy rate of 75% with a live foaling rate of 60% has been 40 mares. 1 , a It is unclear how this traditional value for a Thoroughbred stallion's book was established, but it is likely that it was simply a historical industry maximum based on practical

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate behavioral compliance of horses and ponies with simulated intranasal vaccination and assess development of generalized aversion to veterinary manipulations.

Design—Clinical trial.

Animals—28 light horse mares, 3 pony geldings, 2 light horse stallions, and 3 pony stallions that had a history of compliance with veterinary procedures.

Procedure—Behavioral compliance with 2 intranasal vaccine applicators was assessed. Compliance with standard physical examination procedures was assessed before and after a single experience with either of the applicators or a control manipulation to evaluate development of generalized aversion to veterinary manipulation.

Results—In all 30 horses, simulated intranasal vaccination or the control manipulation could be performed without problematic avoidance behavior, and simulated intranasal vaccination did not have any significant effect on duration of or compliance with a standardized physical examination that included manipulation of the ears, nose, and mouth. Results were similar for the 2 intranasal vaccine applicators, and no difference in compliance was seen between horses in which warm versus cold applicators were used. For 3 of the 6 ponies, substantial avoidance behavior was observed in association with simulated intranasal vaccination, and compliance with physical examination procedures decreased after simulated intranasal vaccination.

Conclusions and Clinical Relevance—Although some compliance problems were seen with ponies, neither problems with compliance with simulated intranasal vaccination nor adverse effects on subsequent physical examination were identified in any of the horses. Further study is needed to understand factors involved in practitioner reports of aversion developing in association with intranasal vaccination. (J Am Vet Med Assoc 2005;226:1689–1693)

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in Journal of the American Veterinary Medical Association

Abstract

Case Description—2 Standardbred racehorses that had been winning races while competing as mares underwent postrace drug testing and had serum testosterone concentrations above the acceptable limit for female racehorses.

Clinical Findings—Initial physical examinations by the referring veterinarian revealed ambiguous external genitalia and suspected intra-abdominally located testes leading to a preliminary diagnosis of male pseudohermaphroditism. Horses were referred for further evaluation of sex. Physical examination of the external genitalia confirmed the findings of the referring veterinarian. Transrectal palpation and ultrasonography revealed gonads with an ultrasonographic appearance of testes. On cytogenetic analysis, both horses were determined to have a 64,XY karyotype and 8 intact Y chromosome markers and 5 SRY gene markers, which were indicative of a genetic male and confirmed an intersex condition. Additionally, both horses had some male-type behavior and endocrinologic findings consistent with those of sexually intact males.

Treatment and Outcome—Taken together, these findings confirmed that both horses were male pseudohermaphrodites. Both horses returned to racing competition as males.

Clinical Relevance—As of October 1, 2008, the Pennsylvania Horse and Harness Racing Commissions implemented a postrace drug testing policy that included analysis of blood samples for anabolic and androgenic steroids and set maximum allowable concentrations of testosterone for racing geldings and females. Within 8 months of initiation of this drug testing policy, the 2 horses of this report were identified as having an intersex condition. This raises the possibility that intersex conditions may be more common in racing Standardbreds than was previously suspected.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To investigate effects of sample handling, storage, and collection time and season on plasma α-melanocyte-stimulating hormone (α-MSH) concentration in healthy equids.

Animals—11 healthy Standardbreds and 13 healthy semiferal ponies.

Procedure—Plasma α-MSH concentration was measured by use of radioimmunoassay. Effects of delayed processing were accessed by comparing α-MSH concentrations in plasma immediately separated with that of plasma obtained from blood samples that were stored at 4oC for 8 or 48 hours before plasma was separated. Effects of suboptimal handling were accessed by comparing α-MSH concentrations in plasma immediately stored at -80°C with plasma that was stored at 25°C for 24 hours, 4oC for 48 hours or 7 days, and –20°C for 30 days prior to freezing at –80°C. Plasma α-MSH concentrations were compared among blood samples collected at 8:00 AM, 12 noon, and 4:00 PM. Plasma α-MSH concentrations were compared among blood samples collected in January, March, April, June, September, and November from horses and in September and May from ponies.

Results—Storage of blood samples at 4°C for 48 hours before plasma was separated and storage of plasma samples at 4°C for 7 days prior to freezing at –80°C resulted in significant decreases in plasma α-MSH concentrations. A significantly greater plasma α-MSH concentration was found in September in ponies (11-fold) and horses (2-fold), compared with plasma α-MSH concentrations in spring.

Conclusions and Clinical Relevance—Handling and storage conditions minimally affected plasma α-MSH concentrations. Seasonal variation in plasma α-MSH concentrations must be considered when evaluating pituitary pars intermedia dysfunction in equids. (Am J Vet Res 2004;65:1463–1468)

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in American Journal of Veterinary Research
History

A 4-year-old Standardbred stallion was retired from racing because of an injury to a tendon in the right forelimb. The owners intended to sell the stallion for use as a stud. A series of prepurchase semen evaluations conducted by personnel at the breeding farm consistently revealed low spermatozoa motility.

The breeding manager also observed that the horse would intermittently turn its head abruptly and gaze toward its groin. The horse would sometimes bite at its flank, kick out with both hind limbs, and pace in a circle. Since early race training when the stallion was 2 years old, it

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in Journal of the American Veterinary Medical Association