REASONS FOR PERFORMING STUDY
There is little information available to define conformational changes with age using an objective but practical method of recording specific body measurements.
OBJECTIVE
To analyse conformation objectively in a population of racing Thoroughbreds and describe the changes from weanling to age 3 years.
METHODS
Annual photographs were taken over 4 years and conformation measurements made from photographs using specific reference points marked on the horses.
RESULTS
Correlation analysis revealed highly significant, moderate to strong relationships between long bone lengths and wither height for all ages. All long bone lengths showed moderate to strong relationships with each other for all ages. The front and rear pastern angles were significantly correlated with the angle of the dorsal surface of the front and rear hooves, respectively, for all. Wither height, croup height and length of neck topline, neck bottomline, scapula, humerus, radius and femur increased significantly from age 0-1 year and age 1-2 years. Hoof lengths (medial and lateral, right and left) grew significantly between the ages of 0 and 1 and 1 and 2 years, but decreased in length between age 2 and 3 years. Horses became more offset in the right limb between weanling and age 3 years, but the offset ratios did not change with age on the left limb. The angle of the scapula (I), shoulder and radiometacarpus significantly increased between all age groups (became more upright). The angle of the dorsal surface of the hooves (both front and hind) decreased significantly from ages 0 to 1 and 1 to 2 years, but showed no significant difference between ages 2 and 3 years.
CONCLUSIONS
A strong relationship between long bone lengths and wither height for all ages supports the theory that horses are proportional. Longitudinal bone growth in the distal limb increased only 5-7% from weanling to age 3 years and is presumably completed prior to the yearling year. Several growth measures increased from ages 0 to 1 and 1 to 2 years, but did not increase from age 2-3 years; indicating that growth rate either slowed or reached a plateau at this time.
POTENTIAL RELEVANCE
This study provides objective information regarding conformation and skeletal growth in the Thoroughbred which can be utilised for selection and recognition of significant conformational abnormalities.
[1]
K. Cunningham.
A study of growth and development in the quarter horse
,
1961
.
[2]
L. D. Van Vleck,et al.
Growth rate of thoroughbreds, effect of age of dam, year and month of birth, and sex of foal.
,
1979,
Journal of animal science.
[3]
J. Campbell,et al.
Radiological estimation of differential growth rates of the long bones of foals.
,
1981,
Equine veterinary journal.
[4]
L. Magnusson.
Studies on the conformation and related traits of Standardbred trotters in Sweden. I. An objective method for measuring the equine conformation
,
1985
.
[5]
G. Dalin,et al.
Retrospective study of hindquarter asymmetry in Standardbred Trotters and its correlation with performance
,
1985
.
[6]
L.-E. Magnusson,et al.
Studies on the conformation and related traits of Standardbred trotters in Sweden. IV. Relationships between the conformation and soundness of 4-year old Standardbred trotters
,
1990
.
[7]
R. A. Long,et al.
Skeletal bone and muscle proportionality in small- and large- framed mature horses of different muscle thickness
,
1988
.
[8]
J Philipsson,et al.
Variation in conformation of Swedish warmblood horses and conformational characteristics of élite sport horses.
,
1990,
Equine veterinary journal.
[9]
O Balch,et al.
Factors involved in the balancing of equine hooves.
,
1991,
Journal of the American Veterinary Medical Association.
[10]
K. Kubo,et al.
Segmental Body Weight, Volume and Mass Center in Thoroughbred Horses
,
1992
.
[11]
A. Barr.
Carpal conformation in relation to carpal chip fracture
,
1994,
Veterinary Record.
[12]
K. Thompson.
Skeletal growth rates of weanling and yearling thoroughbred horses.
,
1995,
Journal of animal science.
[13]
H. Schamhardt,et al.
The influence of conformation on fore and hind limb kinematics of the trotting Dutch Warmblood horse
,
1996
.
[14]
E. P. Kelly,et al.
Linear assessment of the thoroughbred horse: an approach to conformation evaluation.
,
1996,
Equine veterinary journal.