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EQUINE VETERINARY EDUCATION / AE / FEBRUARY 2022


P<0.05; P-values were not adjusted for multiple comparisons (Perneger 1999). Univariable Poisson regression, with robust standard errors


and adjusting for clustering at venue level, was used to calculate incident rate ratios (IRR) and 95% CIs in order to identify factors associated with higher rates of pain-related behaviours and thus higher RHpE scores (Cameron and Trivedi 2009). Robust standard errors were used to control for mild violations of the underlying assumption that the mean and variance of the outcome variable distribution are equal. Variables with Wald P<0.25 following univariable analysis were selected for multivariable Poisson regression modelling. Manual, forward selection was used to build the final multivariable Poisson regression model, with stepwise addition of variables in order of most to least significant based on their Wald P-values. Variables were retained in the final model where Wald P<0.05. Variables not retained in the final model were forced back into the model one at a time to establish if any confounders or interactions had been missed. The fitof the model to the data was assessed using the goodness-of-fit chi-squared test.


Results


Data were available for 151 horse and rider combinations from 10 venues. One horse was excluded following in hand assessment due to grade 5/8 forelimb lameness, thus unless stated otherwise, the data represent 150 horse and rider combinations. Two additional horses, which showed mild lameness in hand, were withdrawn from ridden exercise because they immediately displayed grade 6/8 lameness and were not included in further gait analysis.


Descriptive statistics All descriptive data are presented in Table 1. The horses consisted of 66.0% (n = 99) geldings, 33.3% (n = 50) mares and one stallion and had a median age of 10 years (IQR 8, 14 years; range 3, 27 years). Breed data were available for 149 horses, consisting of 26.9% (n = 40) Warmbloods and Warmblood crosses, 18.8% (n = 28) Cobs, 17.4% (n = 26) Thoroughbreds and Thoroughbred crosses, 16.8% (n = 25) Irish Sports Horses, 10.7% (n = 16) ponies and 9.4% (n = 14) other breeds. The most common work disciplines included General Purpose (n = 85; 56.7%), Riding School (n = 22; 14.7%), Eventing (n = 19; 12.7%) and Dressage (n = 17; 11.3%), with fewest horses in the Show Jumping (n = 4) and Racing/ Endurance/Western (n = 3) disciplines. Of 151 horses, 29.1% (n = 44) showed lameness in hand.


Of 148 horses evaluated ridden, 62.2% (n = 92) exhibited lameness. The median lameness score was 2/8. The total proportion of horses that were lame in hand or while ridden was 79.1% (n = 117/148). More than half of the horses (59.6%, n = 84/141) had gait abnormalities in canter. The median RHpE score for the horses was 8 out of 24 (IQR 5–9; range 0– 15).


Saddle fit was likely to compromise performance in 84.0%


(n = 126) of the horses. Detailed assessment of static saddle fit identified 74.7% (n = 112) of horses had tree points that


were too tight, 27.3% (n = 41) had pommels that were too low, 16.7% (n = 25) had saddles that bridged, and 8.0% (n = 12) had tree points too close to the scapulae. The seat position of the majority of saddles was horizontal (n = 112), while 21.3% (n = 32) tipped backward and six tipped forward.


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Dynamic assessment of saddle fit identified that 57.7% (n = 86/149) of saddles oscillated from side to side, 53.0% (n = 79/149) of saddles bounced dorsoventrally and 45.0% (n = 67/149) of saddles slipped to one side. Noseband type was recorded for all 151 horses. The most


common type of nosebands used included cavesson (40.4%, n = 61), crank flash (13.9%, n = 21), grackle (12.6%, n = 19), crank cavesson (10.6%, n = 16) and Micklem (7.9%, n = 12) nosebands. Less used noseband types included flash (5.3%, n = 8) and drop (3.3%, n = 5) nosebands. Nine horses (6.0%) did not wear nosebands. The median rider score was 2 (IQR 0, 2), with one-third of


riders displaying two abnormalities (33.3%, n = 50). The most common abnormality observed was the rider being seated on the back of the saddle rather than the middle (56.7%, n = 85), followed by the rider being out of balance (54.0%, n = 81), and the rider being too big for the size of the saddle (45.3%, n = 68).


Comparison of lameness and gait abnormalities in hand and when ridden From the same sample of 148 horses, 62.2% were considered lame when ridden, but only 28.4% were considered lame when assessed in hand (difference + 33.8%, 95% CI 22.9, 44.6%; P<0.001). Thirteen horses were considered lame in hand but not when ridden, while 63 horses were considered lame when ridden but not when assessed in hand. Gait abnormalities in canter were not related to in hand lameness (v2 = 1.2, P = 0.28), or lameness when ridden (v2 = 3.3, P = 0.07), when these were assessed individually. However, a combination of in hand or ridden lameness was related to a higher proportion of gait abnormalities in canter (v2 = 13.8, P<0.001).


Noseband type and fit Although the prevalence of mouth opening, as defined by the RHpE, was generally lower when nosebands with the


potential to restrict mouth opening (crank cavesson, crank flash, grackle, Micklem, drop and flash nosebands) were used (30.9%), compared with when a correctly fitted cavesson noseband or no noseband was used (37.3%), this difference was not statistically significant (v2 = 0.7, P = 0.41).


Factors associated with higher Ridden Horse Pain Ethogram scores A Poisson regression model with robust standard errors, including venue (n = 10) as the only explanatory variable, revealed a significant effect of venue on RHpE scores (P = 0.01). The subsequent Poisson regression models were, therefore, adjusted for venue-level clustering. The results of the univariable Poisson regression analysis are presented in Table 2. Fourteen variables were selected for inclusion in the building of the multivariable model. The final multivariable Poisson regression model identified


six variables related to breed, work discipline, lameness status, saddle fit, rider position and noseband type that were significantly associated with RHpE scores (Table 3). Irish Sports Horses had higher RHpE scores compared with Cobs (P = 0.02). Riding School horses had higher RHpE scores compared with horses used for General Purpose (P = 0.001). Although horses used for Racing, Endurance or Western had lower RHpE scores compared with horses used for General Purpose, this finding was based on only three observations.


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