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Commentary on article: The effect of noseband tightening on horses’ behavior, eye temperature, and cardiac responses

Posted by Derek_Major on 18 May 2017 at 12:32 GMT

Commentary on article: The effect of noseband tightening on horses’ behavior, eye temperature, and cardiac responses
Derek Major a

a Derek Major Consulting Pty Ltd, NSW, Australia, derek.major@derekmajorconsulting.com.au


We wish to comment on the research article which was published in the May 2016 edition of the PLOS Journal. [1]
The article reports on a number of measured parameters aimed at determining the physiological and behavioural responses to a common practice in equitation, namely the use of a ‘crank’ noseband. This research builds on previous work of the same group, [2-4] and there is significant cross referencing and overlapping authorship between these and several other publications.

While descriptions have been used elsewhere such as ‘system of pulleys’ and ‘ratcheted shut to clamp the jaws together’ [4] the crank noseband is a simple derivation of the plain cavesson noseband. The ventral aspect of the noseband is connected via a buckled strap, giving a 2:1 mechanical advantage. This facilitates ease of buckling, and would no doubt assist in applying excessive tension in the wrong hands, but the terms used above are somewhat emotive. The Fe ́de ́ration Equestre Internationale clearly would not condone such application. In fact the FEI Dressage Rules, to which the paper refers, state: “Neither a cavesson nose band nor a curb chain may ever be as tightly fixed so as to harm the horse”[5].

In the Introduction, the authors note that “the extreme tightening of nosebands is thought to be increasing in equestrian sport”. This proposal is not supported by data or research, but rather relies on their reference, (McGreevy et al [4]) which in turn refers directly to McLean and McGreevy. [6] This last reference makes scant reference to nosebands, and makes the bald statement: “we see the almost universal use of nosebands so tight that they prevent the horse from opening its mouth….”

This statement is also not supported by data or research. We submit that serial reliance on this remark in subsequent papers substantially weakens the authors’ case.

We have a number of specific concerns about the papers listed above:

1. Proposed pathological effects

Fenner et al propose that “The contemporary crank noseband can be tightened to the extent that it can compromise vascular perfusion [6], and may even cause nerve and bone damage[7]. We are unaware of any clinical reports of such damage, and indeed it is difficult to contemplate how this could occur.

The entire sensory innervation to the nose comes from the infraorbital branch of the trigeminal nerve. The current authors obtained a cadaver head from a local slaughterhouse to demonstrate the anatomical relationship between the nerves and the noseband. When correctly fitted the cavesson rests approximately 1 centimetre rostral to the facial crest. At this point the nerve emerges from the skull but is partially encased in the infraorbital foramen and completely covered by the fleshy muscle levator labii superioris proprius, as indicated in Figure 1. A cadaver head has been sectioned and photographed at the level of noseband placement, and the nerve marked in blue. From this specimen it is also difficult to conceive how any noseband, however tensioned, could impact on the blood supply to the tongue, which is fully contained within the bony structures of the skull.

In the paper by McGreevy et al. 2012 [4], to which Fenner refers, the authors are a little more circumspect in their conclusions on “vascular perfusion”: “This study suggests that horses wearing double bridles and tight nosebands undergo a physiological response to stress response and may have compromised vascular perfusion” (emphasis added).
In Jones and McGreevy 2010[3], to which Fenner further refers, the only reference to ‘nerve’ is in a citation from a human medical reference: “Measurement of hazardous pressure levels and gradients produced on human limbs by non-pneumatic tourniquets”. [7] …. “and references therein”. This paper makes reference to the use of such tourniquets for the emergency management of traumatic amputations on the battlefield. The relevance to nosebands in horses is obscure. “References therein” includes a reference to a chapter entitled “Unsatisfactory Results on Hand Surgery” in a 1987 human surgical text. [8] Under “Occlusion Time and Pressure” tourniquet pressures of 300 to 500 mmHg for up to 3 hours are considered. Casey et al[2] have derived a mathematical prediction of pressure applied by the noseband. Predicted peak pressures ranged from 200 to 400mmHg. This apparently corresponded to periods of peak jaw excursion when horses were simultaneously offered hay or grain, with noseband in place, and while being given “voice and rein cues to backup”. From the graphical display it appears that such pressures were observed for no more than 1-2 seconds at a time. The extrapolation from the human literature here would appear to be unwarranted.
Figure 1 in Casey et al is stated to portray “Chronic trauma at a noseband site likely to have been caused by sustained excessive noseband pressures.” (emphasis added). Causation has not been established here. The lesions shown are located at a site quite distinct from the nerve and blood supply to the nose, as shown in Figure 1 above. One of the current authors (DM) has encountered such lesions on several occasions as a result of negligent long-term application of an ill-fitting headstall, but never from a dressage noseband. The horse depicted by Casey et al (2013)[2] is wearing a bridle, bit and gear quite distinct from that permissible in FEI Dressage competition. The noseband is thin and unpadded, and is connected to a long shank lever action bit, in contradistinction to the noseband discussed in this paper.

2. Case Selection
The authors state that they have deliberately chosen ‘naïve’ horses, i.e. none of them had ever worn a double bridle or a crank noseband. This was done deliberately to “explore the impact of the devices on horses that have not habituated to them”. The justification for this is unclear. In fact, somewhat paradoxically, in the discussion the authors speculate that their test subjects became habituated to wearing two bits in 20 minutes. The horses were not matched for age, gender, breed or prior experience. As the observations were not controlled against other unfamiliar handling procedures such as grooming, saddling or hoof care their correlation with ‘stress’ must be challenged. In fact the authors note a lack of correlation between their measured eye temperature and heart rate variability.

3. Statistical analysis

The authors appear to make inconsistent application of statistical method. For example, they state that “eye temperature then decreased in the NAUN (no area under noseband) recovery period (P<0.001)”. While the inference here is that the tight noseband caused an increased eye temperature, the statistical relevance of this observation must be questioned. The relevant temperature graph has a distorted Y-axis, where the entire range of measurement is less than 0.5 degrees Celsius. Reference to the ThermaCam T604 manual11l that it has an accuracy of plus or minus 2 degrees, a range of over than 4 degrees. (+/-2°C (+/-3.6°F) or +/-2% of reading, whichever is greater, at 25°C (77°F) nominal). There is no data on precision or repeatability. For illustration, we have redrawn the temperature graph (Figure 3), with a “y” axis range of 32 to 38 degrees, and the manufacturer’s stated accuracy range shown to the left:
The paper includes a number of graphs. No uncertainty bars are plotted, and it seems curious that there seems to be no clear trends between “conventional”, “half”, and “no” – “area under noseband”. (See Figure 3). Unless statistical analysis demonstrates statistically significant values for measured parameters at a minimum of 95% uncertainty no valid conclusions can be drawn. The authors make the statement: “We are not declaring differences to be significant or not at a 5% level, rather presenting the actual P value for each difference and allowing the reader to agree or disagree with the conclusions we draw.”

4. The “Five Freedoms”.

The authors make reference to the “Five Freedoms”, which were first proposed in 1965 by the Brambell Committee and which are a laudable endeavour in the assessment of animal welfare. [9] Fenner et al propose that inhibition of yawning and licking behaviour and subsequent “rebound” behaviour is “suggestive of a state of deprivation which may signal compromised welfare”. Their reference is to a paper by Nicol, C entitled “Behavioural responses of laying hens following a period of spatial restriction”[10] which we feel is a questionable extrapolation. A better comparison could have been to compare the effect of a device that also restricts opening of the mouth. For example, Cronin et al [11] investigated the effect of the Husher anti-barking muzzle on dog activity, vocalisation and stress responses comparing pairs of dogs before, during and after one of the pair wore the muzzle for 43 hours. The manufacturer indicates that the muzzle “exerts a firm yet humane pressure around the snout” [12]. This is a behavioural inhibition which closely parallels the application of a noseband to a horse. Cronin et al [11] found that the dogs barked less and moved less when muzzled but the muzzled dogs showed rebound increased activity when the muzzle was removed. However, no differences were found in cortisol measures for the unmuzzled and muzzled dogs. They hypothesise that this rebound may be due to the reduced activity that preceded it or because of the enforced inactivity increased the motivation to perform the behaviour so when they have the opportunity, they perform the behaviour.
By way of contrast, Casey et al [2] also raise the question of behavioural deprivation in this context, but note that “the transience of their effect may mitigate their overall effect”, referring further to Jones and McGreevy.[3] In the last paper Jones and McGreevy seek to rationalise behavioural deprivations in terms of impact and duration. Intuitively many equestrian activities, for example exercise and competition, cause intermittent disruption to behaviours such as eating, social interaction and sexual behaviour. Inhibition of licking and yawning for perhaps 1 hour out of 24 would seem to rank low on the scale of impact and duration.

In conclusion, we are fully supportive of research into horse welfare but submit that the commentaries that we have discussed here are not based on secure scientific or statistical methodology.

1. Fenner, K., et al., The Effect of Noseband Tightening on Horses’ Behavior, Eye Temperature, and Cardiac
Responses. PloS one, 2016. 11(5): p. e0154179.
2. Casey, V., et al., A preliminary report on estimating the pressures exerted by a crank noseband in the horse.
Journal of Veterinary Behavior: Clinical Applications and Research, 2013. 8(6): p. 479-484.
3. Jones, B. and P.D. McGreevy, Ethical equitation: applying a cost-benefit approach. Journal of Veterinary
Behavior: Clinical Applications and Research, 2010. 5(4): p. 196-202.
4. McGreevy, P., A. Warren-Smith, and Y. Guisard, The effect of double bridles and jaw-clamping crank
nosebands on temperature of eyes and facial skin of horses. Journal of Veterinary Behavior: Clinical
Applications and Research, 2012. 7(3): p. 142-148.
5. FEI, Federation Equestre Internationale Dressage Rules. Lausanne, Switzerland: FEI, 2015. 20.
6. McLean, A.N. and P.D. McGreevy, Ethical equitation: Capping the price horses pay for human glory. Journal of
Veterinary Behavior: Clinical Applications and Research, 2010. 5(4): p. 203-209.
7. McEwen, J. and V. Casey. Measurement of hazardous pressure levels and gradients produced on human limbs
by non-pneumatic tourniquets. in Proceedings of the 32nd Conference of the Canadian Medical and Biological
Engineering Society. 2009.
8. McGraw, R., J. McEwen, and R. McFarlane, The tourniquet. Unsatisfactory results in hand surgery. New York:
Churchill Livingstone, 1987: p. 5-13.
9. Brambell, F.W.R., Report of the Technical Committee to Enquire into the Welfare of Animals Kept Under
Intensive Livestock Husbandry Systems: Presented to Parliament by the Secretary of State for Scotland and
the Minister of Agriculture, Fisheries and Food by Command of Her Majesty December, 1965. 1965: HM
Stationery Office.
10. Nicol, C.J., Behavioural responses of laying hens following a period of spatial restriction. Animal Behaviour,
1987. 35(6): p. 1709-1719.
11. Cronin, G., et al., An anti-barking muzzle for dogs and its short-term effects on behaviour and saliva cortisol
concentrations. Applied Animal Behaviour Science, 2003. 83(3): p. 215-226.
12. Husher, http://www.husher.com.au/....
13. Wuhan, www.thermalimaging.com.au....


No competing interests declared.