A comment on bit-related lesions in Icelandic horses.
Jens Tolboll Mortensen, as a private person
8 December 2014
In Acta Veterinaria Scandinavica 2014, 56:40 Björnsdottir et al presented an investigation on Icelandic horses, in which they concluded that bit related lesions in the mouth was a general problem in competition horses and that the use of a particular bit, curb bit with a port, was a decisive risk factor for lesions on the bars of the mandible.
The study included repeated examinations of the horses reaching the finals. There were no records on the bit used during the training before the competition and no information on the horses temper (will and spirit). The effect of the rider was not included in the analysis.
The results showed more lesions in the bar region after the second examination and a correlation between the use of a snaffle bit and lesions in the buccal region and between the use of a curb bit with port and lesions in the bar region.
Confounding by indication, the phenomenon in my medical world where treatments tend to look harmful just because they are only given to sick people, may explain these results. Meaning in this respect, that the curb bit with port might be used more often with horses that are difficult to ride and therefore are at a higher risk of developing lesions, maybe irrespective of the bit used. Another way of saying this is that the indication for treatment may be related to the risk of future health outcomes.
Given the conclusions in this study, I think it would have been interesting to include the temper of the horse, the bit used during training and the rider in the analysis before announcing a causal relationship to a specific bit.
Yours sincerely,
Jens Tølbøll Mortensen, MD, PhD,
Kollerup Strandvej 11,
DK-9690 Fjerritslev,
Denmark.
E-mail: kollerupstrandvej11@mail.dk.
Competing interests
None.
Authors’ response to Dr Jens Tøbøll Mortenssen’s comments to our article Bit-related lesions in Icelandic competition horses
Sigridur Bjornsdottir, Icelandic Food and Veterinary Authority
9 December 2014
The comments include three major concerns.
1. Temper (will and spirit) of the horse should be included as a risk factor for bit-related lesions.
The two competitions, where this study took place, represented the highest level of the equestrian sport in Iceland. Horses coming to the finals in those competitions are regarded as the best trained and best talented horses in the country and they were exclusively ridden by professional riders. The temper of the horse is judged and contributes to the score for some of the disciplines included in this study (4 and 5 gaited gæðingakeppni) and therefore horses with an optimal temper have most likely been overrepresented in the finals. As mentioned in the discussion, a curb bit with a port might be of help in controlling the horses (especially those who are extremely willing or excited) and that might be one of the reasons why some riders choose to use it for some horses. However, we didn’t regard this to be the main reason for the use of the bits and therefore, temper or willingness wasn’t likely to be a confounder. It‘s argued that an effect on the head and neck carriage might be the main reason for using curb bits with a port as an extreme high neck carriage with a vertical position of the head is highly awarded. Curb bits with a port were most frequently used for horses that qualified for the finals in the tölt competition, T1 (83%). In our opinion, it would be difficult to argue that horses competing in that discipline should have a more extreme temper compared to the four- and five-gaited tests, but the demand for head and neck carriage is clearly the highest in T1.
The results indicated that horses that were ridden with curb bits with a port in the preliminary rounds were rather successful in qualifying to the finals. At the same time many of those horses developed lesions in the bar region. Horses ridden with other types of bit did not have lesions in that location, with one exception. Biological reasoning for this is explained in the paper.
In our opinion, the strong association between the use of curb bits with a port and the presence of lesions on the bars is very important information, especially from an animal welfare point of view and should not be misinterpreted and compared to the use of medication on sick patients.
The expression “causal relationship“ is not used in the article. We used the term decisive risk factor for the association between the use of curb bits with a port and lesions in the bar region because the association was very strong (OR= 75), highly significant (P=0.009) and no other risk factors were detected. The type of bit definitely influenced both the location and the severity of the lesions.
We strongly disagree with the statement that there is a risk of “confounding by indication, meaning in this respect, that the curb bit with port might be used more often with horses that are difficult to ride and therefore are at a higher risk of developing lesions, maybe irrespective of the bit used“. Our opinion is further supported with data from 2014, clearly demonstrating that banning the use of curb bit with a port in competition was an effective preventive measure.
2. Bit used during training should be included as a risk factor for bit-related lesions.
For most horses, different types of bits have been used during training prior to the competitions. This is shortly mentioned in the discussion section. The initial examination, prior to the competition is in fact reflecting the training period. At that time, only few horses were found with severe lesions in the bar region. That might indicate that curb bits with a port are not used as much or in milder way during training.
Most of the horses with lesions in the bar region developed those during the competitions. It was therefore of most relevance to correlate the lesions with the bit used in the performance prior to the latest mouth control.
3. Rider should be included as a risk factor for bit-related lesions.
Since approximately 62% of riders rode only one or two horses there was an obvious risk of confounding effects between bit and rider. This is explained in the article. Adding the variable rider to the multivariable model was, however, tested and found insignificant.
Below is a summary of a report from the Icelandic Food and Veterinary Authorities regarding the mouth control of competition- and breeding horses at the two major equestrian events in Iceland in 2014 including a comparison to corresponding data from 2012.
Report from mouth control of competition- and breeding horses at the two major equestrian events in Iceland in 2014 and comparison to data from 2012:
Preventive measures for bit-related lesions in the mouth were implemented in 2014 with emphasis on information to the riders and elimination of risk factors. New rules banning the use of curb bits with a port in competition were put in force by the Icelandic Equestrian Association in the spring of 2014. Comparable rules were, however, not ready for use in breeding shows.
This report is based on 1066 records from the examination of 602 horses competing in 5-gaited tests, 4-gaited tests, tölt, young riders, or presented at breeding show in 2014. The results reveal decisive reduction of the frequency of bit-related lesions compared to 2012. This is demonstrated by an increased frequency of horses with no such findings, both in breeding and competition (Tables 1-3). The reduction in the frequency of lesions in the corners of the mouth and the adjacent buccal mucosa, found in both competition and breeding horses, is most likely a result of the increased attention put on the equine oral health and the riders’ attempt to prevent lesions.
Severe lesions located in the bar region had almost disappeared in the competition horses. This change was clearly a result of the ban of the use of curb bits with a port as the same trend was not demonstrated for horses presented in breeding shows, where those bits were still in use. Some thickening of the soft tissue in the bar region, regarded as mild ,was however, a common finding . In some cases it was reflecting the past (scar tissue) but also indicating pressure on this area within the limits of severe tissue damage.
For the first time, lesions in the gingiva adjacent to the first check teeth (P2) in the lower jaw were recorded. Although those were usually rather small, they tended to be sore and in those cases were classified as severe. The lesions were most likely due to pressure from the bit although they were in some cases found in horses having other problems (especially horses chewing on the bit).
A total of 38 breeding horses had severe lesions on the bars of the mandible, most often characterized by prominent thickening or inflammation connected to the underlying bone. Nine of them also had ulcers on the top of the lesion and were consequently withdrawn from further participation. Most of the horses with records of a severe lesion on the bars, prior to the second presentation (61%), had been ridden with double jointed curb bits with a port in their first presentation. One horse had been ridden with an unjointed curb bit with a port. Ordinary Icelandic curb bits had been used for 26% of the horses, in some cases because findings at the first examination resulted in warnings against the use of bits with a port.
Severe lesions on the bars of the mandible were on the other hand only recorded in one competition horse.
The results demonstrated the positive effect of the preventive measures implemented. Enlightening riders in regard to equine oral health helped in reducing the frequency of lesions in the corners of the mouth but the ban of the use of curb bits with a port was found to be necessary in regard to lowering the frequency of severe lesions in the bar region.
Table 1. Records from examination of the rostral part of the mouth of competition horses and breeding horses prior to the preliminary rounds or first presentation at the two major national horse events in Iceland in 2012 and 2014
Table 2. Records from examination of the rostral part of the mouth of competition horses and breeding horses prior to the semi-finals or second presentation at the two major national horse events in Iceland in 2012 and 2014
Table 3. Records from examination of the rostral part of the mouth of competition horses and breeding horses prior to the finals or award presentation at the two major national horse events in Iceland in 2012 and 2014
Acta Veterinaria Scandinavica
A comment on bit-related lesions in Icelandic horses.
8 December 2014
In Acta Veterinaria Scandinavica 2014, 56:40 Björnsdottir et al presented an investigation on Icelandic horses, in which they concluded that bit related lesions in the mouth was a general problem in competition horses and that the use of a particular bit, curb bit with a port, was a decisive risk factor for lesions on the bars of the mandible.
The study included repeated examinations of the horses reaching the finals. There were no records on the bit used during the training before the competition and no information on the horses temper (will and spirit). The effect of the rider was not included in the analysis.
The results showed more lesions in the bar region after the second examination and a correlation between the use of a snaffle bit and lesions in the buccal region and between the use of a curb bit with port and lesions in the bar region.
Confounding by indication, the phenomenon in my medical world where treatments tend to look harmful just because they are only given to sick people, may explain these results. Meaning in this respect, that the curb bit with port might be used more often with horses that are difficult to ride and therefore are at a higher risk of developing lesions, maybe irrespective of the bit used. Another way of saying this is that the indication for treatment may be related to the risk of future health outcomes.
Given the conclusions in this study, I think it would have been interesting to include the temper of the horse, the bit used during training and the rider in the analysis before announcing a causal relationship to a specific bit.
Yours sincerely,
Jens Tølbøll Mortensen, MD, PhD,
Kollerup Strandvej 11,
DK-9690 Fjerritslev,
Denmark.
E-mail: kollerupstrandvej11@mail.dk.
Competing interests
None.Authors’ response to Dr Jens Tøbøll Mortenssen’s comments to our article Bit-related lesions in Icelandic competition horses
9 December 2014
The comments include three major concerns.
1. Temper (will and spirit) of the horse should be included as a risk factor for bit-related lesions.The two competitions, where this study took place, represented the highest level of the equestrian sport in Iceland. Horses coming to the finals in those competitions are regarded as the best trained and best talented horses in the country and they were exclusively ridden by professional riders. The temper of the horse is judged and contributes to the score for some of the disciplines included in this study (4 and 5 gaited gæðingakeppni) and therefore horses with an optimal temper have most likely been overrepresented in the finals. As mentioned in the discussion, a curb bit with a port might be of help in controlling the horses (especially those who are extremely willing or excited) and that might be one of the reasons why some riders choose to use it for some horses. However, we didn’t regard this to be the main reason for the use of the bits and therefore, temper or willingness wasn’t likely to be a confounder. It‘s argued that an effect on the head and neck carriage might be the main reason for using curb bits with a port as an extreme high neck carriage with a vertical position of the head is highly awarded. Curb bits with a port were most frequently used for horses that qualified for the finals in the tölt competition, T1 (83%). In our opinion, it would be difficult to argue that horses competing in that discipline should have a more extreme temper compared to the four- and five-gaited tests, but the demand for head and neck carriage is clearly the highest in T1.
The results indicated that horses that were ridden with curb bits with a port in the preliminary rounds were rather successful in qualifying to the finals. At the same time many of those horses developed lesions in the bar region. Horses ridden with other types of bit did not have lesions in that location, with one exception. Biological reasoning for this is explained in the paper.
In our opinion, the strong association between the use of curb bits with a port and the presence of lesions on the bars is very important information, especially from an animal welfare point of view and should not be misinterpreted and compared to the use of medication on sick patients.
The expression “causal relationship“ is not used in the article. We used the term decisive risk factor for the association between the use of curb bits with a port and lesions in the bar region because the association was very strong (OR= 75), highly significant (P=0.009) and no other risk factors were detected. The type of bit definitely influenced both the location and the severity of the lesions.
We strongly disagree with the statement that there is a risk of “confounding by indication, meaning in this respect, that the curb bit with port might be used more often with horses that are difficult to ride and therefore are at a higher risk of developing lesions, maybe irrespective of the bit used“. Our opinion is further supported with data from 2014, clearly demonstrating that banning the use of curb bit with a port in competition was an effective preventive measure.
2. Bit used during training should be included as a risk factor for bit-related lesions.For most horses, different types of bits have been used during training prior to the competitions. This is shortly mentioned in the discussion section. The initial examination, prior to the competition is in fact reflecting the training period. At that time, only few horses were found with severe lesions in the bar region. That might indicate that curb bits with a port are not used as much or in milder way during training.
Most of the horses with lesions in the bar region developed those during the competitions. It was therefore of most relevance to correlate the lesions with the bit used in the performance prior to the latest mouth control.
3. Rider should be included as a risk factor for bit-related lesions.Since approximately 62% of riders rode only one or two horses there was an obvious risk of confounding effects between bit and rider. This is explained in the article. Adding the variable rider to the multivariable model was, however, tested and found insignificant.
Below is a summary of a report from the Icelandic Food and Veterinary Authorities regarding the mouth control of competition- and breeding horses at the two major equestrian events in Iceland in 2014 including a comparison to corresponding data from 2012.
Report from mouth control of competition- and breeding horses at the two major equestrian events in Iceland in 2014 and comparison to data from 2012:
Preventive measures for bit-related lesions in the mouth were implemented in 2014 with emphasis on information to the riders and elimination of risk factors. New rules banning the use of curb bits with a port in competition were put in force by the Icelandic Equestrian Association in the spring of 2014. Comparable rules were, however, not ready for use in breeding shows.
This report is based on 1066 records from the examination of 602 horses competing in 5-gaited tests, 4-gaited tests, tölt, young riders, or presented at breeding show in 2014. The results reveal decisive reduction of the frequency of bit-related lesions compared to 2012. This is demonstrated by an increased frequency of horses with no such findings, both in breeding and competition (Tables 1-3). The reduction in the frequency of lesions in the corners of the mouth and the adjacent buccal mucosa, found in both competition and breeding horses, is most likely a result of the increased attention put on the equine oral health and the riders’ attempt to prevent lesions.
Severe lesions located in the bar region had almost disappeared in the competition horses. This change was clearly a result of the ban of the use of curb bits with a port as the same trend was not demonstrated for horses presented in breeding shows, where those bits were still in use. Some thickening of the soft tissue in the bar region, regarded as mild ,was however, a common finding . In some cases it was reflecting the past (scar tissue) but also indicating pressure on this area within the limits of severe tissue damage.
For the first time, lesions in the gingiva adjacent to the first check teeth (P2) in the lower jaw were recorded. Although those were usually rather small, they tended to be sore and in those cases were classified as severe. The lesions were most likely due to pressure from the bit although they were in some cases found in horses having other problems (especially horses chewing on the bit).
A total of 38 breeding horses had severe lesions on the bars of the mandible, most often characterized by prominent thickening or inflammation connected to the underlying bone. Nine of them also had ulcers on the top of the lesion and were consequently withdrawn from further participation. Most of the horses with records of a severe lesion on the bars, prior to the second presentation (61%), had been ridden with double jointed curb bits with a port in their first presentation. One horse had been ridden with an unjointed curb bit with a port. Ordinary Icelandic curb bits had been used for 26% of the horses, in some cases because findings at the first examination resulted in warnings against the use of bits with a port.
Severe lesions on the bars of the mandible were on the other hand only recorded in one competition horse.
The results demonstrated the positive effect of the preventive measures implemented. Enlightening riders in regard to equine oral health helped in reducing the frequency of lesions in the corners of the mouth but the ban of the use of curb bits with a port was found to be necessary in regard to lowering the frequency of severe lesions in the bar region.
Table 1. Records from examination of the rostral part of the mouth of competition horses and breeding horses prior to the preliminary rounds or first presentation at the two major national horse events in Iceland in 2012 and 2014
COLUMN 1, TABLE 1
R1. Preliminary rounds
R2.
R3. Competition 2012
R4. Breeding 2012
R5. Competition 2014
R6. Breeding 2014
COLUMN 2, TABLE 1
R1.
R2. n
R3. 350
R4. 208
R5. 362
R6. 240
COLUMN 3, TABLE 1
R1. No findings
R2. 0
R3. 189 54%
R4. 121 58%
R5. 267 74%
R6. 163 68%
COLUMN 4, TABLE 1
R1. Lesions in the corners of the mouth/cheeks
R2. mild
R3. 101 29%
R4. 49 24%
R5. 56 15%
R6. 36 15%
COLUMN 5, TABLE 1
R1. Lesions in the corners of the mouth/cheeks
R2. severe
R3. 18 5%
R4. 9 4%
R5. 11 3%
R6. 2 1%
COLUMN 6, TABLE 1
R1. Lesions on the bars
R2. mild
R3. 29 8%
R4. 21 10%
R5. 28 8%
R6. 31 13%
COLUMN 7, TABLE 1
R1. Lesions on the bars
R2. severe
R3. 13 4%
R4. 8 4%
R5. 0
R6. 8 3%
--------------------------------------------------
Table 2. Records from examination of the rostral part of the mouth of competition horses and breeding horses prior to the semi-finals or second presentation at the two major national horse events in Iceland in 2012 and 2014
COLUMN 1, TABLE 2
R1. Semi-finals/ second round
R2.
R3. Competitions 2012
R4. Competitions 2014
R5. Breeding 2014
COLUMN 2, TABLE 2
R1.
R2. n
R3. 91
R4. 87
R5. 230
COLUMN 3, TABLE 2
R1. No findings
R2. 0
R3. 35 38%
R4. 63 72%
R5. 104 45%
COLUMN 4, TABLE 2
R1. Lesions in the corners of the mouth/cheeks
R2. mild
R3. 35 38%
R4. 11 13%
R5. 49 21%
COLUMN 5, TABLE 2
R1. Lesions in the corners of the mouth/cheeks
R2. severe
R3. 7 8%
R4. 0
R5. 4 2%
COLUMN 6, TABLE 2
R1. Lesions on the bars
R2. mild
R3. 7 8%
R4. 12 14%
R5. 48 21%
COLUMN 7, TABLE 2
R1. Lesions on the bars
R2. severe
R3. 7 8%
R4. 1 1%
R5. 25 11%
--------------------------------------------------
Table 3. Records from examination of the rostral part of the mouth of competition horses and breeding horses prior to the finals or award presentation at the two major national horse events in Iceland in 2012 and 2014
COLUMN 1, TABLE 3
R1. Finals/ awards
R2.
R3. Competitions 2012
R4. Competitions 2014
R5. Breeding 2014
COLUMN 2, TABLE 3
R1.
R2. n
R3. 77
R4. 68
R5. 79
COLUMN 3, TABLE 3
R1. No findings
R2. 0
R3. 31 40%
R4. 45 66%
R5. 45 57%
COLUMN 4, TABLE 3
R1. Lesions in the corners of the mouth/cheeks
R2. mild
R3. 20 26%
R4. 12 18%
R5. 10 13%
COLUMN 5. TABLE 3
R1. Lesions in the corners of the mouth/cheeks
R2. severe
R3. 2 3%
R4. 1 <1%
R5. 4 5%
COLUMN 6, TABLE 3
R1. Lesions on the bars
R2. mild
R3. 7 9%
R4. 10 15%
R5. 4 5%
COLUMN 7. TABLE 3
R1. Lesions on the bars
R2. severe
R3. 17 22%
R4. 0
R5. 16 21%
--------------------------------------------------
Author: Sigríður Björnsdóttir DVM PhD.
Competing interests
None declared