ORIGINAL

Prevalence of stereotypies in thoroughbred race horses at Club Hípico Concepción, Chile

Prevalencia de estereotipias en caballos fina sangre de carrera del Club Hípico Concepción, Chile

Lisandro Muñoz A,¹* M.Sc, Felipe Ainardi C,¹ MV, Christian Rehhof V,¹ MV, Jaime Cruces L,¹ MV, Reinaldo Ortiz R,¹ MV, Mario Briones L,² M.Sc.

¹Universidad de Concepción, Facultad de Ciencias Veterinarias. Departamento de Ciencias Clínicas, Victoria 495. Concepción, Chile.
²Universidad de Concepción, Facultad de Ciencias Veterinarias. Departamento de Ciencias Pecuarias, Victoria 495. Concepción, Chile.

*Correspondence: lismunoz@udec.cl

Received: September 2013; Accepted: February 2014.

ABSTRACT

Objective. To determine the prevalence of classic stereotypies in Thoroughbred racehorses at the Club Hípico Concepción (CHC) in Chile and its association with sex and age. Materials and methods. The entire population of resident horses at the CHC was studied (n=341). Each horse trainer (n=23) was asked for the name, sex and age of the horses under his/her supervision. After that, all the animals were continuously observed inside their stalls for 8 hours by only one person, to record the absence or presence of classic stereotypies (cribbing, weaving, stall-walking). To analyze the data, the animals were divided by sex into 3 groups: stallions, geldings and mares. According to age, they were divided into 2 groups: < 5 years old and 5 years old or more. Descriptive statistics were used and association was tested using the chi square test using p≤0.05. Results. 13.2% of all CHC's horses displayed stereotypies: cribbing (4.99%), weaving (2.93%) and stall-walking (5.28%). No association was found between the presence of stereotypies and sex or age. Conclusions. Thoroughbred race horses at the CHC showed a high prevalence of classic stereotypies, especially stall-walking.

Key words: Cribbing, equine, stall-walking, stereotyped behavior, weaving (Source: MeSH).

RESUMEN

Objetivo. Determinar la prevalencia de estereotipias clásicas en caballos fina sangre de carrera (FSC) del Club Hípico Concepción (CHC), Chile y su asociación con el sexo y la edad. Materiales y métodos. Se estudió la totalidad de los caballos FSC (n=341) residentes en el CHC. A cada entrenador (n=23), se le consultó nombre, sexo y edad de los caballos a su cargo. Luego, con la finalidad de detectar la presencia o ausencia de estereotipias clásicas (aerofagia, balanceo y caminar en pesebrera), durante 8 horas una sola persona observó directamente los caballos mientras se encontraban en sus pesebreras. Los caballos se dividieron por sexo en 3 grupos: machos enteros, machos castrados y hembras. De acuerdo con la edad se dividieron en 2 grupos: <5 años y 5 años o más. Los resultados en la parte descriptiva se entregan como porcentajes simples y para el análisis estadístico de las variables sexo y edad, se utilizó la prueba de X2, con un nivel de significancia de p<0.05. Resultados. El 13.2% de los caballos de CHC presentaron estereotipias: aerofagia (4.99%), balanceo (2.93%) y caminar en pesebrera (5.28%). No se encontró asociación entre la presencia de estereotipias y las variables sexo y edad. Conclusiones. Los caballos FSC del CHC presentan una alta prevalencia de estereotipias clásicas, principalmente caminar en pesebrera.

Palabras clave: Aerofagia, balanceo estereotipado, caminar en pesebrera, comportamiento estereotipado, equino (Fuente: MeSH).

INTRODUCTION

In the wild, horses live in groups of 3-10 individuals, providing them with security and allowing them to have intense social interaction. They can also walk up to 65 to 80 km (1) and spend about 80% of the day feeding (2). For this reason, captivity and handling associated with domestication have compromised their nutritional, social, sexual and kinetic behavior, which in some horses has stimulated the development of abnormal behaviors and stereotypies. Stereotypies are defined as repetitive behavior that is relatively unchanged and has no apparent function (1). Therefore, the presence of a stereotypy is indicative of a welfare problem (2). In horses, the most common stereotypies (also called classic stereotypies) are cribbing, weaving and stall-walking. In some countries, these stereotypies must be declared at auctions, and in general, tend to decrease the price of horses (1). Worldwide, several studies have been performed to determine the frequency and risk factors associated with these stereotypies (3-20). However, within the risk factors, sex and age have shown very contradictory results (1,3,9-13,16,19-23). However, none of the studies' results were based on information obtained from direct observation of an entire determined population, but from direct observation of a sample of a population (13,16,20) or on information provided by the owners through personal interviews or surveys conducted at a distance by telephone, mail or email (3-12,14,15,17-19).

The aim of this study was to determine, by direct observation, the prevalence of classic stereotypies in all Thoroughbred racehorses (FSC) at the Concepción Equestrian Club (Chile) and their association with gender and age.

MATERIALS AND METHODS

Study site and geo-climate. Concepción Equestrian Club (CHC), Biobío Region, Chile (36°47'32”S; 73°05'44”W). Warm temperate climate with dry summers, high humidity and less than 50 m above sea level (24).

Animals studied. All Thoroughbred horses residing at the CHC were studied (n=341), with an age range of 2-13 years. All were enclosed for more than 22 hours a day in individual stalls with shavings, without any physical contact with other horses, without access to paddocks or pastures, and kept on a diet of grain, hay and water ad libitum. All horses had a similar training program that consisted of one or more of the following activities performed 1 or 2 times a day: walking (20-30 minutes), galloping riderless in a round pen (20 minutes) and galloping with a rider at different intensities (5-10 minutes). Horses that were competing the following day would not receive exercise.

Recording Stereotypies. Each trainer (n=23), was asked the name, sex and age of the horses in their care. Then, based on an ethogram (Table 1) and with the purpose of identifying and detecting the presence or absence of classic stereotypies (or cribbing, weaving and stall-walking), a continuous recording system (25) was used. The study was conducted between January 3^rd and February 25^th, 2008. Each day, and per block (where there are several individual stalls whose doors open onto a hallway or common area) for 8 hours divided into two direct, continuous observation periods (8:00 to 13:00 hours and 14:00 to 17:00 hours), one person directly observed all horses while they were in their stalls. The horses were divided by sex into 3 groups: stallions (n=50), geldings (n=173) and mares (n=118). They were also divided into 2 groups according to age: <5 years (n=213) and 5 years or more (n=128).

Analysis of results. The results in the description are presented as percentages. For statistical analysis of the sex and age variables, the X^{2 test} was used, and alternatively Fisher's exact test was used when a result was <5. Both tests had a significance level of p ≤ 0.05.

RESULTS

Forty-five (13.2%) of the horses at CHC had stereotypies: 17 (4.99%) cribbing, 10 (2.93%) weaving and 18 (5.28%) stall-walking. Table 2 shows the prevalence of classic stereotypies in Thoroughbred horses at CHC according to sex.

No association was found between the presence of individual and total classic stereotypies in connection to the sex variable (p> 0.05).

Table 3 shows the prevalence of classic stereotypies in Thoroughbred horses at CHC according to age.

No association was found between the presence of individual and total classic stereotypies in connection to the age variable (p> 0.05).

DISCUSSION

The prevalence of classic stereotypies found in horses at CHC is well within the range reported in other studies, which varies between 0.7 and 66% (3-20), and is one of the highest worldwide. In fact, it is the highest reported prevalence among studies done on competing Thoroughbreds (4,6,8,9,20) and those done in South America on Chilean rodeo horses (16, 19), sport horses (18), racehorses (20) and military horses (14) which have been reported a frequency of classic stereotypies of 2.32 to 10%. As stereotypies have not been reported in free horses (1), the high prevalence of stereotypies found in CHC horses could be explained in part by a greater breed predisposition, reported for Thoroughbreds (4,6,10-13,15), associated with the nervous or reactive temperament of this breed (11). The high prevalence may also be hereditary, as it has been shown that there are families with a prevalence 5 to 10 times higher than the average observed in a determined population of Thoroughbred horses (4).

However, as pointed out by several studies, daily handling conditions are more important than breed. The risk factors to which the CHC horses are subjected are: stabling for more than 22 hours a day (6,21), confinement in individual stalls without physical contact with other horses (6,11,19), use of shavings as bedding material (20,21), no access to a paddock or to grazing (8,11), prepared feed (1), mainly concentrated (6,11,12) and a lower rate of foraging (6,12,19,21). In relation to sex, no significant association with the classic stereotypies was found, which is consistent with other studies (3,11,12,16,22).

Tadich et al (19) in a study of 325 Chilean horses, found a significant association (p<0.0001) between sex and the appearance of stereotypies, being that they are more common in stallions than in castrated males and females. The finding was justified by these researchers based on the social isolation that stallions are subjected to in Chile, by being kept in paddock and stalls without physical contact and at times without eye contact with other horses. On the other hand, the present study and Tadich et al (19), differ completely with findings reported by Mills et al (9) who conducted a study of 4061 Thoroughbreds, and found that the prevalence of classic stereotypies was higher in geldings (6.9%) and mares (6.4%) than in stallions (3%). They suggest that the increased risk in castrated horses may be associated with stress caused by the Gonadectomy which they have undergone.

These contradictory results suggest that sex is not a risk factor in horses without sexual experience and that the reported differences might be more related to specific handling than to the sex itself. Not finding a significant increase in the overall prevalence of stereotypies associated with age is consistent with reported results in other studies (1,11,16). This result was not expected, since it has been reported that the prevalence of stereotypies increases with age (1,10,11,19,20), partly because once stereotypies are acquired, they are very difficult to eliminate (1) and because horses face stressful situations and other risk factors that could stimulate the development of a stereotypy (3) on a daily basis. But on the other hand, due to the fact that some owners believe that stereotypies are imitated (9), and negatively affect health (1,4) and performance (1,9), there is a high probability that a significant percentage of horses with stereotypies have, after a while, been withdrawn from CHC for poor performance.

In this study there was a tendency in this respect only for stall-walking. This is consistent with results reported by Mills et al (9), who found that 16.4% of 2 year old Thoroughbreds had some stereotypies, a percentage that decreased drastically up to 6 years of age, not because the stereotypies were gone, but because most of the horses with stereotypies had been sold due to declining performance.

Regarding cribbing, with or without support, the prevalence found is within the range reported in other studies, which varies between 0.4 and 14.08% (3-6, 8-12, 14-16, 18-20). However, it is the highest prevalence among studies conducted in South America, where the reported range does not exceed 2.8% (14,16, 18-20) and the second highest among studies conducted on Thoroughbred horses competing in Italy, Sweden, Australia, UK, USA and Chile that reported frequencies between 2.15 and 13.3% (4,6,8,9,15,20). This high prevalence, and the observed stereotypies in general, could be related to a genetic predisposition (4,10,15) since a prevalence of 30% cribbing has been reported in some families of Thoroughbreds when the average was 2.4 % (4). The high prevalence could also be associated with handling by the breeder before arriving at the CHC, such as abrupt weaning (10,26), receiving concentrated feed post-weaning (1,10), since according to one study the highest percentage of foals with cribbing display it between 3 and 9 months of age, and at an average age of 5 months (10). In addition, there are risk factors associated with routine handling at CHC that can stimulate the development of cribbing such as not using straw bedding (3,20), no access to pasture (3,8,26), receiving small amounts of forage (3,7,21), receiving a highly concentrated diet (3,7,26) and not having physical contact with other horses (3,15,19,26).

Normando et al (22) indicate that the type of bedding material does not affect the prevalence of cribbing. Christie et al (3) and Albright et al (15) also suggest that when there is a lack of visual and physical contact the prevalence of cribbing doubles (12.3%) when compared with horses that have access to pasture (5.9%), only eye contact (5.9%) or limited visual and physical contact (5.6%), therefore stress associated with isolation could cause this increase (15,19). Regarding age, and coinciding with the results of this study, other studies also indicate that it is not a risk factor (3,16,20,21,23). However, sex is more contradictory due to the fact that in many studies no association has been found (3,6,20,21), Mills et al (9) found that cribbing was higher in castrated males than in females and stallions. The study differs from another done ​​by Tadich et al (19) on Chilean horses, where stallions had a higher frequency of cribbing (p = 0.001) than castrated males and females, suggesting that this could be more related to social isolation than to sex. Furthermore, the same study found that stallions who both competed in the Chilean rodeo and were used as sires in the same period had a higher risk of displaying stereotypies than those engaged in only one function (19).

In regard to weaving, also called swaying (2), the prevalence found is well within the range reported in other studies conducted in both South America and the rest of the world, which varies 0.1 to 50% (3-6,8,10,13,14,16-20), and is close to the average of other studies of Thoroughbred horses competing in Italy, Sweden, Australia, Chile and the United Kingdom, where reported frequencies are between 0.1 and 5% (4,6,8,20). Among the risk factors associated with weaving is heritability (4,11). In a study of 1035 Thoroughbreds in Italy where the weaving average was 2.5%, in some families it was 26% (4). Although not unanimous (10), other studies indicate that breed is a risk factor, the most prevalent breeds being Thoroughbred (11,13) and Arab (17), perhaps associated with their more reactive temperament (13) or with the athletic activity that they perform (6). It has also been observed in Thoroughbred competing that the prevalence is higher in horses stabled all day than those who had access to pasture for a few hours (8,21).

Christie et al (3) found no association with access time to a pasture. They have also identified other risk factors such as not having access to a paddock (22), receiving less than 6.4 kg of forage per day (21) and being a brood mare mother without young (17). Furthermore, Ninomiya et al (13) suggest that it could be imitated by means of social learning; however, Clegg et al (27), discard that. With regard to gender, the results are contradictory because, like the present study, others indicate no other association with weaving (3,10,16,19,28). However, the study by Mills et al (9) conducted in 4061 horses indicated that the frequency of weaving was higher in females (2.13%) than in stallions (0.57%) and geldings (0.63%). Also, the study conducted by Tadich et al (20) on 743 competing Thoroughbreds reported that the frequency was higher in females (3.04%) and stallions (2.52%) than in geldings (0.48%). With regard to gender, there was a striking result from the study conducted by Behjahali et al (17) on breeding Arabian mares, which reported that 21.9% of broodmares displayed weaving, suggesting a relationship with sex. However, in that same study, of the 25 females with weaving, just 1 was foaling and the rest had no nursing young with them. The reported difference between mares with or without a nursing foal in that study could be explained by the hormonal state associated with lactation or most likely by a social aspect associated with having or losing the mother-foal bond.

Regarding age, the study conducted by Waters et al (10) showed that the average age of onset for weaving was week 60. In another study Christie et al (3) found that the frequency was higher in individuals older than 10 years of age, which they justified by noting that increasing age increases the likelihood of encountering stressful situations. However, other studies conducted on competing horses showed no differences associated with age (12,16,19).

With regard to stall-walking, also called box-walking (2), the prevalence found was well within the range reported in other studies in both South America and the rest of the world, which varies between 0.2 and 8.8% (4-8,10,13,16-20), and is the fourth highest worldwide. But, the highest among the studies performed on Thoroughbred horses competing in Italy, Sweden, Australia, Chile and the United Kingdom reported frequencies from 0.2 to 3.9% (4,6,8,20,21). Although it is believed that the cause is associated with social needs (1), two studies have shown that there is a genetic predisposition (4,10) and that there has been a prevalence of stall-walking of 13% in some Thoroughbred families in circumstances where the average for the same study was 2.5% (4). However, other studies indicate that risk factors are also: lack of physical contact with other horses (11), no access to pasture (8,11,28) and breed, as it is reported to be more common in Thoroughbred (6,11) Arab (17) and Warm-blood horses, perhaps for being more reactive breeds (11). It is speculated that the cause may be motivation to keep moving, frustration or little environmental stimulation (1). With regard to sex, some studies indicate that this would not be a risk factor (9-11,19,22). Although Muñoz et al (16), in a study performed on 100 Chilean horses, found that it was significantly more frequent (p<0.05) in stallions (6%) than in females (0%), suggesting that it could be associated with the handling to which they are subjected in Chile because they remain stabled all day, without physical contact and sometimes without eye contact with other horses.

On the contrary Tadich et al (20) observed that stall-walking in Thoroughbreds was more common in mares (3.72%) than in geldings (1.44%) and stallions (0.42%). Regarding age, the average age of onset for stall-walking is 64 weeks (10) and this should increase with age (1). However, in accord with the present study, no association between the prevalence of stall-walking and age (11,16,19,28) was found. Although, in this study, a decreasing trend was observed for this stereotypy in horses 5 years of age or more, which suggests that horses that display stall-walking are discarded due to poor performance.

It is suggested that the prevalence of stereotypies in general and stall-walking in horses at CHC, the highest reported in competing Thoroughbred horses, is a consequence of the stressful handling they undergo at the CHC, which does not allow the expression of normal social, nutritional, sexual and kinetic behavior. On the other hand, not finding an association between the presence of stereotypies and sex could result from a similar handling of individual horses without general sexual experience, or maternal experience in the case of females. Finally, not finding a significant increase in stereotypies associated with age could explain why a significant percentage of horses with stereotypies are discarded from competition for low performance, which apparently occurs mainly in horses that display stall-walking.

In conclusion, Thoroughbred horses at the CHC have a high prevalence of classic stereotypies, mainly stall-walking.

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