Proceedings of a Workshop on - The Havemeyer Foundation

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Havemeyer Foundation Monograph Series No. 11 LONG-TERM LONGITUDINAL STUDY OF LARYNGEAL FUNCTION IN 187 FOALS J. G. Lane Department <strong>of</strong> Clinical Veterinary Science, University <strong>of</strong> Bristol, Langford House, Langford, Bristol, BS40 5DU, UK The sale <strong>of</strong> foals to be retained to go into training or to be resold as yearlings – ‘pin-hooking’ – forms a major component in the marketplace for Thoroughbred horses. Prospective purchasers seek to take precautions to ensure that the animals concerned will be suitable for resale, or can be trained effectively for racing. It has become fashionable for foals to be subjected to endoscopic examinations on behalf <strong>of</strong> prospective purchasers prior to sale. Some breeders also seek endoscopic examinations <strong>of</strong> foals ahead <strong>of</strong> sales if only for peace <strong>of</strong> mind. However, is endoscopy <strong>of</strong> foals a worthwhile procedure and are the results dependable? A number <strong>of</strong> congenital structural abnormalities <strong>of</strong> the upper respiratory tract (URT) can be diagnosed accurately by a combination <strong>of</strong> palpation and endoscopy (Embertson 1997). These conditions include midline clefts and other defects <strong>of</strong> the palate, pharyngeal and subepiglottal cysts and fourth branchial arch defects. These abnormalities are collectively relatively unusual and arise in no more than 0.5% <strong>of</strong> Thoroughbreds born (see page 49). A major interest for foal purchasers <strong>of</strong>ten centres on laryngeal function and the identification <strong>of</strong> recurrent laryngeal neuropathy (RLN). To assess the reliability <strong>of</strong> the interpretation <strong>of</strong> laryngeal function, a group <strong>of</strong> 197 foals were examined by endoscopy and 187 were available for reexamination one year later. The video-endoscopic records were reviewed ‘blindly’ – the findings are shown in the Table 1 and the obvious conclusion is that there are inconsistencies in the 2 series <strong>of</strong> results. The laryngeal function <strong>of</strong> some foals appeared to be within normal limits, but then to TABLE 1: Comparison <strong>of</strong> laryngeal function <strong>of</strong> 197 foals with the same horses one year later Yearling grades (187) 1 (32) 2 (112) 3 (37) 4 (6) 5 (0) NA 1 (36) 12 14 4 0 0 6 2 (123) 17 86 16 1 0 3 Foal grades (197) 3 (29) 3 11 12 2 0 1 4 (9) 0 1 5 3 0 0 5 (0) 0 0 0 0 0 0 10 horses (NA) were not available to be examined as yearlings TABLE 2: Comparison <strong>of</strong> the laryngeal function grading <strong>of</strong> 187 yearlings with their median winnings between 2 and 4 years <strong>of</strong> age Laryngeal grade 1 2 3 4 5 (32) (112) (37) (6) (0) Median Winnings (£) 1933 5358 5367 724 0 31
Equine Recurrent Laryngeal Neuropathy have ‘deteriorated’ over the following 12 months, while others, which would have been considered unsuitable had they been examined prior to sale as foals turned out to be totally normal. There was no foal or yearling in the group studied which was afflicted with any <strong>of</strong> the congenital abnormalities mentioned above. In summary, endoscopy <strong>of</strong> foals is not an absolutely dependable technique and decisions on whether to buy or to reject should not be based upon this technique. A review <strong>of</strong> subsequent racing performances at 2, 3 and 4 years <strong>of</strong> age showed that the median stakes winnings <strong>of</strong> the yearlings in this study were greatest in the Grade 3 group (Table 2). REFERENCES Embertson, R.M. (1997) Weanling and yearling upper airway evaluation. In: Current Techniques in Equine Surgery and Lameness Eds: N.A. White and J.N. Moore. Philadelphia: W.B. Saunders Co. 122- 127. 32
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