The Effectiveness Of Young Horse Evaluation Biology Essay

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Promoting and improving the elite population of sport horses has proved problematic in latter years on a global scale (Gharahveysi et al., 2010). Extensive training is required to produce a horse at international and advanced levels in any discipline therefore reproduction is not of significant importance when reaching a peak in career, often resulting in decreased fertility rates and reproductive performance when breeding becomes a viable option (Ricketts and Alsonso, 1991). Consequently, a lengthy generation interval, as average age of breeding is between 8 and 12 years, is witnessed within the sport horse industry (Burns et al.,2004).

The development of artificial insemination and embryo transfer allows for minimal disruption in athletic career, reducing the generation interval; however it is deemed beneficial if talent is proven before these techniques are used. Nevertheless, providing the equine industry with a breeding value depending on natural ability of a horse from a young age will further soothe this issue and encourage breeding, ultimately enhancing the elite population.

The British Equestrian Federation (BEF) has been appointed as the governmental body in the United Kingdom to monitor and promote "British Breeding" as one of its roles. The Futurity Scheme was established in 2005 by BEF to conduct testing and evaluate the young sport horse population within the British Isles, with the aim to indicate potentially superior equines (British Equestrian Federation, 2010). These schemes are beneficial to the equine breeding industry by aiding the reduction in generation interval and to ensure that young horses with a greater natural ability are placed in the correct training environment to maximise their potential.

The Young Horse Evaluations series, designed to test the athleticism of 4-year olds, is one of the strategies of the Futurity scheme, and is an adaptation of the Riding Horse Quality Test and station performance tests (Kearsley, 2008). Young horses scoring highly enter a championship at the end of each year, owners and trainers of these horses are invited to join training and informative sessions to exploit and encourage the talent of these horses throughout their training and career. The 4 year old Young Horse Evaluation Series is constantly undergoing assessment and amendment to improve the efficacy of results. The aim of this study is to appraise the capability of the current methods of testing and evaluation to determine the worth of scores produced from YHE in predicating potentially successful animals within the equine sporting industry.

Literature Review

Environment

With relation to genetic theory, phenotype is dependent on genetic status and environmental factors (P=G+E) (Posthuma, 2003). An exhaustive list of environmental factors affecting performance and ability may be obtained. Despite obtaining superior scores from the Young Horse Evaluation Series, environmental conditions have the ability to influence a horse to such an extent that it may not go on to compete at elite level, thus indicating the importance of the mutually influential relationship between environment and appeared value of young horse evaluation series score. Research of the environmental influences that act as precursors for success appear minimal with relation to Young Horse Evaluation. Stewart et al., (2010) reported 11.5% of phenotypic variance depending on the permanent environment of the horse. Whilst some methods of analysis used in young horses testing such as, best unbiased linear predictors, allow for environmental influences, their potency should not be ignored.

Nutrition

Diet of the performance horse requires continual manipulation in order to meet energy requirements and maintenance demands (Frape, 1994). Malpractice predisposes horses to metabolic disorders often resulting in physical weaknesses, such as laminitis (Menzies-Gow, 2010) gastric ulceration (Reese and Andrew, 2009), osteochondritis dissecans (Kronfield et al.,2005) and exertional rhabdomyolysis (Aleman, 2008). Furthermore, Stewart et al., (2010) suggested that height is significantly related to dressage ability and performance; with dressage scores increasing 0.75% between heights of 142cm and 188cm. Suboptimal nutrition, particularly in the young horse, will inhibit growth (Lewis, 1995; Pagan and Deor, 2001).

Consequently, these factors affect the longevity of career and viability of the animal. However, provision of the optimum diet throughout growth, training and competitive life will maximise natural potential (Kronfield et al., 1994; Lepeule et al.,2009). With relation to the Young Horse Evaluation Series, nutrition will affect the performance of the horse, therefore suboptimal nutrition through training may limit the competitive status of the horse and thus YHE result may not correlate with future performance record.

Injury

Musculoskeletal injuries are the primary cause of wastage in sports horses (de Cocq and Munsters, 2010). Murray et al., (2006) identified a correlation between skill level and prevalence of injury in the eventing horse, stating that injury prevalence is significantly increased (P=0.0004) with skill level, however a significant difference is not seen in any other discipline. Furthermore, this study indicated a relationship between discipline and type of injury, with certain sports having a higher susceptibility to certain catastrophic injuries. Elevation of subchondral bone thickness of the tarsal has been identified in horses working at elite level when compared with general purposes horses (Murray et al., 2006b). Thickening of subchondral bone is linked with joint degenerative injuries (Norradin et al., 1998). Whilst catastrophic injury will result in death, injuries resulting in periods of rest mean a lack of training and competition, restricting advances in career.

Poor conformation predisposes a horse to injury (Burns, 2004). Conformation is largely associated with natural form, however, conformation can be altered greatly by injury. Therefore injuries caused in training and competition may alter a horses gait and movement impeding performance. Horses that have incurred injury during the career will have distorted competition results, not necessarily providing a true representation of their ability and thus may not correlate with YHE score.

Training

Training method affects athletic ability and longevity (Burns et al.,2004; Koenen et al.,2004). The lack of standardised training methods means horses will excel and be limited in differing disciplines (de Cocq and Munsters, 2010). Furthermore the ability of a horse to learn is completely individual and therefore training programmes specific to each horse have been proven to exact superior performance (Murphy and Arkins, 2007), however it is rarely feasible at large training yards to develop individual programmes. Additionally it has been reported that trainability is directly related with emotionality and aptitude for learning (Cooper, 1998) (McCall, 1990).

Inadequate level of fitness for competition encourages fatigue, and subsequent injury thus affecting competition result (Roneus et al.,1994; Shashak and Hill, 1995). Apoptosis, programmed cell death, of skeletal muscle is significantly increased (P=<0.005) in the untrained horse in response to exertional exercise (Boffi et al., 2002). The detriments of overtraining have been extensively documented, stating that excessive and/or intense training will inevitably lead to injury (Kuipers and Keizer, 1988; Kuipers and van Breda, 2003; Hinchkliff et al., 2008; Hamlin et al., 2002). Boston and Nunamaker (2000) concluded that incorporating galloping in exercise programmes of 2-year old Thoroughbreds increased hazard ratio of injury to 0.3 ± 0.1/mile galloped in comparison with breezing 4.2 ± 1.5/mile. McGowan et al.,(2002) concluded that overtraining resulted in a decreased levels of basal muscle glycogen in overtrained horses with comparison to normally trained horses. Training method, intensity and frequency can optimise or inhibit athletic capability, thus affecting their competition results.

Rider Influences

Rider ability will influence the dynamic patterns of a horse. Peham et al., (2001) speculated that an advanced rider will have a significantly (p=<0.05) lower deviation on variability of gait than the recreational rider. Moreover, Kearlsey (2008) concluded that 18% of phenotypic variance was a result of rider influence. Visser et al., (2008) discussed the effects of rider personality and cooperation of the horse, it was speculated that personality did play a role in cooperation with emotionally reactive horses.

Peham et al.,( 2004) saw marked differences in forward velocity and acceleration following comparison of movement in an ill-fitting, and well-fitting saddle, with standard deviations varying from 103.1 in a correctly fitted saddle, and 170.35 in an ill-fitting saddle. DvoÅ™áková et al., (2009) saw that joint action was altered when lead by different leaders, particularly in stride lengths (1.69 m and 1.80 m) and stride speed (1.39 m.s₋₁ and 1.49 m.s₋₁). The ability of human contact to interfere with dynamic conformation plays an important role not only in rideability and level of performance of the horse but ultimately scores at Young Horse Evaluation Series and competition.

Stress and the Competitive Environment

Competitive environments are a source of stress for horses. Cortisol, a hormone released in response to stress, induces catabolism of skeletal muscle and suppresses production of cytokines vital for the inflammatory response thus increasing the risk of injury (Storey, 2004). Peeters et al.,(2010) witnessed significant increases in salivary cortisol levels from horses at home (0.5960.40 nM) in comparison with competition (2.136 1.49 nM). Morgan et al., (2001) concluded that cortisol levels secreted in response to stress affected performance variance by 31% in humans. Additionally, Cayado et al.,(2006) concluded that competition induced a significant increase in cortisol and ACTH in response to both dressage and show-jumping in the novice horse, in comparison with horses experienced in the competitive environment.

Covalesky et al.,(1992) suggested that horses that had been regularly exposed to competitive environments showed minimal differences in heart rate, behaviour and plasma cortisol levels between show and home environments. Experience in the competitive environment is therefore vital prior to YHE evaluation; horses with minimal experience are likely to undergo stress responses thus inhibiting natural movement and performance.

Surface Type and Condition

Training surfaces and competitive surfaces can act as precursors for injury and have the ability to alter stride kinematics depending on material and management practices (Ratzlaff et al.,2005). Chateu et al., (2010) witnessed changes in stride frequency, length, duration of stance phase and hoof slipping depending on differing surfaces (See Table 1: Adapted from Chataeu et al., 2010).

Table 1: Mean (s.d) (n=120 strides) acceleration, velocity, displacement of the hoof, ground reaction force at impact and stride parameters for 4 horses trotting on 2 different tracks of a sand beach with decreasing water content:firm wet sand (FWS), deep wet sand (DWS), deep dry sand (DDS) and on an asphalt road (ASPH) (Adapted from Chataeu et al., 2010).

Speed

(m/s)

Hoof sliding

(x)

(cm)

Stance Duration

(ms)

Stride length (m)

FWS

7.20

(0.53)

4.6

(1.7)

163.5

(12.5)

4.21

(0.29)

DWS

6.65

(0.72)

4.1

(2.0)

181.6

(18.2)

3.84

(0.44)

DDS

4.64

(0.47)

2.1

(1.4)

231.6

(21.7)

2.76

(0.29)

Asph

4.23

(0.30)

5.2

(3.2)

206.7

(20.2)

2.81

(0.23)

Kai et al., (1999) investigated the effects that rough or poorly managed surfaces had on limb kinematics and therefore perceived dynamic conformation. It was concluded that rough track surfaces had an effect on the vertical hoof forces and resultant hoof balance. Furthermore, dust exposure will predispose both horse and human to respiratory difficulties and disease (Kirkhorn and Garry, 2000; Schneker, 2000; Woods et al., 1993). Studies document the effects of damp arena surfaces and thus increased levels of endotoxins in causing respiratory disease in the equine and dry dusty arena sufaces causing performance inhibiting diseases and conditions such as inflammatory airway disease (IAD) and.... (Barton et al., 2001; Mazman and Hoffman, 2003). Poor management of arena surfaces will lead to increased dust exposure. With relation to YHE, the ménage surface used for training could predispose a horse to respiratory conditions thus limiting athletic capability. Furthermore temporary limitation of the respiratory system could be caused by a badly managed surface at Young Horse Evaluation resulting in coughing and decreased performance.

Shoeing

Roepstorff et al., (1999) witnessed significant differences in the stance phase of movement between horses that were shod and unshod, altering mid stance loading and rollover, furthermore, significant differences (P=<0.05) in fetlock, tarsal and hood angular velocity thus indicating an observational difference in dynamic movement. Willeman et al.,(1997) concluded that the shod horse has an improved quality of gait in comparison with the unshod horse. From this, it could be speculated that the use of shoes will promote desired movement of the horse, and therefore boost YHE scores, however, poor farriery will result in debilitated locomotion and often infection and/or injury.

Transportation

Smith et al., (1996) reported elevated levels of packed cell volume, red blood cell count, haemoglobin, plasma protein and cortisol and decreased body weight post transportation indicating stress and dehydration is experienced during travelling. Dehydration will impinge performance, as it induces impaired thermoregulatory responses (Hinchcliff et al.,2008). (HINCHCLIFF P392), citations 67-69) ..... and ..... found in humans that a loss of 2-3% of body weight will impair the body's ability to transfer heat from core to periphery, raising core temperature and thus resulting in further dehydration as increased sweating is induced.

Furthermore, it has been stated that transport stress will make horses more susceptible to performance inhibiting disorders such as diarrhoea, colic, laminitis and rhambdomyolysis (Owen et al.,1983; Bell and Lowe, 1986; Kuwano et al., 1997; Shinobu et al., 1992). Giovagnoli et al., (2002) found that repeated muscle contraction during transportation to maintain balance, particularly with inexperienced drivers, could contribute to rhabdomyolysis and injury. It could be speculated that horses that are inexperienced with travelling will receive low scores at YHE evaluation.

Testing: Methods of Practice

The current testing methods for young horse evaluation vary greatly between breed organisation, governmental body and country (Bruns et al., 2001). Whilst aims may differ slightly between breed organisations, all are ultimately aiming to produce the most elite lines of equine athlete. The variation between testing method must be compared to deduce the most effective practice in terms of cost, standardisation and repeatability of testing, assessment of most heritable traits, and ensuring horses are placed into the most suitable career for their ability as well as maximising longevity of career.

Format of Testing

The three modes of testing young horses include station performance tests, field performance tests and competition performance (Bowling and Ruvinsky, 2000). The station performance test varies in length depending country and breeding organisation (Thoren-Hellsten et al., 2006). The station test follows a standardised method allowing for repeatability, however only a limited number of horses may be evaluated using this method due the restricted capacity of testing facilities and expense (Koenen, 2002). Station testing is a widely used method, its application is seen in Great Britain, Sweden, Hungary, Denmark, Germany and Ireland. Thoeren-Hellsten et al., (2006) assessed the efficacy of these methods by evaluating studies conducted in Germany, Denmark and Sweden (See Table 2: Adapted from Thoren Hellsten et al., 2006).

Table 2: Heritability for traits recorded at station tests (adapted from Thoren Hellsten et al., 2006)

Test Trait

I

II

III

IV

V

VI

VII

VIII

IX

X

Walk

0.73

0.32

0.20

0.25

0.43

0.34

0.34

0.46

0.45

Trot

0.65

0.28

0.23

0.37

0.50

0.45

0.51

0.37

0.34

Canter

0.54

0.25

0.54

0.33

0.47

0.36

0.42

0.39

0.28

Free jumping

0.30

0.71

0.70

0.42

0.47

0.39

0.47

0.55

Jumping

0.31

0.35

0.32

0.38

0.47

0.38

0.33

0.32

0.50

Rideability

0.64

0.46

0.56

0.30

0.52

0.44

0.41

Cross Country Manner

0.41

0.15

0.15

0.20

Character

0.52

Dressage ability

0.35

Jumping ability

0.39

I-II Dutch Studies, III-VIII German Studies, IX-X Swedish Studies

I: Huizinga et al., (1991), II: Van Veldhuizen (1997), III: Jaitner and Reinhardt (1993), IV: Uphaus et al., (1994), V: Schade (1996), VI: von Velsen-Zerweck (1998), VII: Brockmann (1998), VIII: Luhrs-Behnke et al., (2002), IX: Gerber Olsson et al., (2000) , X: Gelinder et al., (2001)

Field testing is conducted in over a period of day, thus allowing for a larger volume of horses to be tested than witnessed in station performance testing (Wallin et al., 2003). Ricard et al., (2000) reported a low correlation between field test results and competition data (0.65) in comparison with station performance testing (0.70-0.90). It could be speculated that the cost effectiveness of this technique compromises accuracy. However, Wallin et al., (2003) reported high correlations between gait trait scores and dressage competition results (0.63-0.75). Additionally it was reported that jumping ability and competition results were highly correlated (0.83-0.93); suggesting that certain trait scores taken from field performance tests should be more highly regarded than others.

Nevertheless, heritability of field testing was analysed from numerous sources by Thoren- Hellsten et al., (2006) these results support the same theory as Ricard et al., (2000) that field performance testing delivers less accurate results (See Table 3: Adapted from Thoren-Hellsten et al., 2006).

Table 3: Heritability for traits recorded at field performance tests (adapted from Thoren Hellsten et al., 2006)

Test Trait

I

II

III

IV

V

VI

VIIa

VIIb

Walk

0.22

0.37

0.26

0.27

0.27

0.35

0.39

Trot

0.14

0.50

0.30

0.36

0.36

0.41

0.38

Canter

0.18

0.25

0.25

0.29

0.34

0.35

0.32

Rideability

0.03

0.21-0.27

0.24-0.29

0.30

Jumping

0.15

0.46-0.62

0.27-0.30

0.20-0.49

0.37

0.25-0.35

0.21

Balance

0.37

Character

0.06

Dressage ability

0.36

Jumping ability

0.54

I-II Dutch Studies, IV-VI German Studies, VIIa-b Swedish Study. I: Huizinga et al., (1990), II: Van Veldhuizen (1997), III: Durco et al., (2002), IV: Uphaus et al., ( 1994), V: Schade (1996), VI: Brockmann (1998), VIIa: Gelinder et al.,(2002).

Competition Performance

The efficacy of competition performance results in predicting successful horses is scrutinized due to low heritability correlations discovered by numerous researchers (Bowling and Ruvinsky, 2000). Age at time of testing will affect the apparent efficacy of competition results; Huzinga and Van der Meij (1989) reported that heritability's decrease with age, therefore results will appear more accurate in young horses. Competitions are categorised depending on assessed level, giving 4 classes of group; there has been much deliberation of the efficacy of heritability scores between these classes. Aldridge et al., (2007) found that scores for the low level groups were more highly correlated with later performance than the high level groups. Hassenstein (1998) however, disputed this stating that heritability correlations were lowest for the more quality groups than the lower groups.

Young horse competition performance is often used as a means of secondary testing; for example the Cycle Classique in France and Belgium.

Trait Assessement

Static assessment

Dynamic Asseessment

Certain methods may be better for certain disciplines and or traits

Scoring System and Judge

Scale of 1-10

Influence of environmental factors metioned in previous section

Judge bias

Measurements of Success

How is success measured?

Earning not neccasarily a true representation of standard as may consitiantly be place 3rd and win prize money, therefore have higher earnings that a horse less goes out on a less regular basis but always wins.

Analysis of Scores

BLUP's

Industry Involvement

Participants

Length of testing

Disciplines they may be better for

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