Bit-related injuries were common among a group of trotters examined in a recent study in Finland.
Kati Tuomola and her colleagues, reporting in the journal Frontiers in Veterinary Science, note that oral lesions in the bit area are common in horses, but not comprehensively studied in harness racing horses.
The researchers found that 84% of the 261 horses examined had acute lesions in the bit area after racing. More than half (56%) had more than one acute lesion.
“In fact, many had three to four lesions, and in some cases, as many as five or six,” the researchers reported.
The 84% of the horses found with acute lesions was a similar result to that found in a study of Swedish trotters, with lesions found in 88% of the horses examined.
The data for the study was collected during a welfare program for trotters conducted by the Finnish Trotting and Breeding Association.
The area in and around the mouth likely to be affected by the bit was systematically examined in the 261 horses after racing. The horses comprised 151 Standardbreds, 78 Finnhorses, and 32 ponies, aged between 3 and 15.
The checks were undertaken using a bright light source without sedation or a mouth gag.
Any lesion found was graded on a points scale, with the points then tallied for each horse.
Based on the overall score, the horses were divided into four groups: Group A had no lesions; B had mild lesions; C had moderate lesions; and D and severe lesions.
The 84% found with acute lesions represented 219 of the 261 horses examined.
In total, 21% (55/261) had mild lesions, 43% (113/261) had moderate lesions, and 20% (51/261) had severe lesions.
Despite these numbers, visible bleeding outside the mouth was observed in only six of the horses, representing 2%.
Further, 5% of the horses (13/261) had blood on the bit when it was removed from the mouth, even though no blood could be seen outside the mouth.
“The absence of blood outside the mouth does not rule out serious injuries inside the mouth,” the researchers said.
According to the Finnish racing guidelines, official racetrack veterinarians should only examine horses after a race if they show bleeding from the mouth.
Only 12% (32/261) of all the horses examined had no acute or old mucosal lesions in the bit area.
The authors said the scoring system developed and used for the study could be used for evaluating the severity of oral lesions in different equestrian disciplines and populations to allow for comparable data across studies.
Lesion grading systems used in earlier studies were all unique to each study, and none of them accounted for the number, depth, and size of the lesions, they noted.
The researchers did not evaluate soreness or pain to palpation since it would have been difficult to evaluate horses with a high sympathetic tone after a race performance.
“Interestingly, the two horses with the highest acute lesion scores were extremely difficult to examine.
“Two of the three horses that were too difficult to examine and were excluded from the study, had blood on the bit. We suggest that these difficulties during examination and extraordinary behavior were related to oral pain.”
The full study team comprised Tuomola, Minna Kujala-Wirth, Anna Mykkänen and Anna Valros, all with the University of Helsinki; and Nina Mäki-Kihniä, an independent researcher in Finland.
Tuomola K, Mäki-Kihniä N, Kujala-Wirth M, Mykkänen A and Valros A (2019) Oral Lesions in the Bit Area in Finnish Trotters After a Race: Lesion Evaluation, Scoring, and Occurrence. Front. Vet. Sci. 6:206. doi: 10.3389/fvets.2019.00206