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Hintze, S., Smith, S., Patt, A., Bachmann, I., & Würbel, H. (2015). What eye wrinkles in horses tell us about their emotional state. In Proceedings of the 3. International Equine Science Meeting.
Abstract: Wrinkles above the eye ball are common in domestic horses but may differ in number and shape both between and within individuals. They are caused by contraction of the inner eye brow raiser, and some people working with horses call them “worry wrinkles”, considering them to reflect emotional states. However, as yet no study has formally investigated the relationship between eye wrinkles and emotional state in horses.
The aim of the present study was to induce states of different emotional valence and to assess whether positive emotional states would reduce the expression of eye wrinkles while negative emotional states would increase it. Sixteen horses were confronted in a balanced order with two presumably positively and two negatively valenced situations each. Positive situations included anticipation of a food reward (FA) and petting (P), negative situations included food competition (FC) and waving a plastic bag (PB). Each situation lasted for 60s (TRT) and was preceded by a 60s control phase (CON). Throughout CON and TRT pictures of the eyes were taken, and for each horse four pictures per situation (FA, P, FC, PB) and phase (CON and TRT) were randomly selected (n = 512) and scored in random order and blind to treatment for six outcome variables: overall impression (qualitative), number, angle and markedness of eye wrinkles, presence of eye white, and shape of eye lid.
Data were analysed separately for the right and left eye using linear mixed effects models (angle, number), generalised linear mixed models (eye white, markedness), and ordered logistic regression (qualitative, shape of eye lid), with “situation” (FA, P, FC, PB), “phase” (CON, TRT) and their two-way interaction as fixed effects.
Expression of eye wrinkles did not vary consistently across “situation” and “phase”. Independent of phase, eye white appeared less frequently during P than during FA (z=-3.15, p=0.009), FC (z=-2.94, p=0.02), and PB (z=4.17, p<0.001) in the left eye and during PB (z=4.10, p 0.001) in the right eye. Similarly, wrinkles were less marked during P compared to the other situations in the left eye (FA: z=3.15, p=0.009; FC: z=-2.94, p=0.017; PB: z=4.17, p<0.001) and compared to PB in the right eye (z=4.10, p=0.001), while no differences between situations occurred in number of wrinkles, overall impression and shape of eye lid for both eyes. Consistent with our hypothesis, P induced relaxation of the underlying muscle in the right eye resulting in a wider angle compared to its control phase (interaction situation*phase: F3,10=3.71, p=0.055; post-hoc comparison: z=-3.57, p=0.009), while FC induced muscle contraction, resulting in a sharper angle in the left eye (interaction situation*phase: F3,11=6.57, p=0.011; z=3.73, p=0.005).
We conclude that emotional valence may affect characteristics of eye winkle expression in horses which might therefore be a promising indicator of horses’ emotional states, but further research is needed to validate the relevant outcome variables.
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Toewe, B., Fey, K., & Würbel, H. (2008). Effect of an omeprazole (GastroGard) treatment on cribbiting in horses suffering from gastric ulceration. In IESM 2008.
Abstract: Cribbiting is a common stereotypy in domestic horses and is associated with stress and low fibre/high concentrate diets, which are known to cause gastric inflammation and ulceration. Recent studies indicate that antacid supplements can reduce both gastric inflammation and cribbiting. However, stereotypies are also associated with altered brain functions and these are thought to be responsible for emancipation. Emancipation refers to a process by which stereotypies become increasingly independent of the causal factors and may therefore persist with age, regardless of the conditions. Emancipation complicates therapy and points to the importance of prevention.
To further examine the relationship between gastric health and cribbiting and its relation to age at onset, we examined the effect of the proton-pump inhibitor omeprazole (GastroGard, Merial) on gastric inflammation/ulceration and on cribbiting in a double-blind placebo-controlled study. Thirty-one horses of different sex, breed and age were randomly allocated to treatment and placebo and divided into three groups depending on age: 0-5 years (n=11), 5-10 years (n=11) and >10 years (n=9), whereby age at onset of cribbiting was ≤ 5 years for all horses. Treatment and placebo were administered orally by syringe once every day for 28 days by the horse owners. Treatment consisted of 4mg/kg omeprazole for the first four days and 1mg/kg for the following 24days.
Using scan sampling and behaviour sampling, general activity and the number of crib-bites were assessed in the home pens one day before and one day between day 21 and 28 of treatment. Observations were made for three hours each around morning and evening feeding times, respectively. Prior to pre-treatment observations and after post-treatment observations, the horses were transported to the clinic and endoscoped for signs of inflammation and ulceration in the oesophagus, the squamous area, the glandular area and the first part of the duodenum using a common scoring system (Andrews et al. 1999).
All 31 horses showed signs of gastric inflammation/ulceration which decreased significantly from a median score of 1,2 to 0,6 in the treatment group (Wilcoxon signed rank test, z=-3,186, p=0,001), while there was no change in the placebo group (z=-0,577, p=1.0). However, there was no significant difference in cribbiting before and after treatment, neither in the treatment group (z=-1,834, p=0,068), nor in the placebo group (z=-0,415, p=0,734). Moreover, there were no significant effects of age on gastric inflammation/ulceration (2-way ANOVA, F=1,112, p=0,345) or cribbiting (F=1,113, p=0,344).
These results contrast with the recent studies on the effects of antacids on gastric health and cribbiting. There are two possible explanations for this: First, cribbiting may become rapidly established and may thus have persisted even in the youngest age group. Second, omeprazole acts specifically by reducing gastric acid secretion into stomach, while antacids may also have an effect on the intestine. However, these results shed doubts on the hypothesis that cribbiting is caused by gastric inflammation/ulceration.
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Würbel,. Mating Stategies of male donkeys in a promiscuous mating system Diss Bern. Doctoral thesis, , Bern.
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Würbel, H. (1990). The relationship between social structure and mating system in donkeys & Mating strategies of male donkeys in a promiscuous mating system"l structure and mating system in donkeys &. Diploma thesis, , Faculty of Natural Sciences, University of Berne, Switzerland.
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