Abstract: The long-term effects of gestational immaturity in the premature (defined as < 320 days gestation) and dysmature (normal term but showing some signs of prematurity) foal have not been thoroughly investigated. Studies have reported that a high percentage of gestationally immature foals with related orthopedic issues such as incomplete ossification may fail to fulfill their intended athletic purpose, particularly in Thoroughbred racing. In humans, premature birth is associated with shorter stature at maturity and variations in anatomical ratios, linked to alterations in metabolism and timing of physeal closure in the long bones. We hypothesized that gestational immaturity in horses might similarly be associated with reduced height and different anatomical ratios at maturity. In this preliminary study, the skeletal ratios of horses with a history of gestational immaturity, identified through veterinary and breeder records, were compared with those of unaffected, closely related horses (i.e., sire, dam, sibling). External measurements were taken from conformation photographs of cases (n = 19) and related horses (n = 28), and these were then combined into indices to evaluate and compare metric properties of conformation. A principal component analysis showed that the first two principal components account for 43.8% of the total conformational variation of the horses' external features, separating horses with a rectangular conformation (body length > height at the withers), from those that are more square (body length = height at the withers). Varimax rotation of PC1 and analysis of different gestational groups showed a significant effect of gestational immaturity (P = .001), with the premature group being more affected than the dysmature group (P = .009, P = .012). Mean values for the four dominant indices showed that these groups have significantly lower distal limb to body length relationships than controls. The observed differences suggest that gestational immaturity may affect anatomical ratios at maturity, which, in combination with orthopedic issues arising from incomplete ossification, may have a further impact on long-term athletic potential.
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The research article investigates the long-term effects of premature and dysmature birth on a horse’s height and limb length. The study suggests that these early birth conditions might interfere with the animals’ anatomical proportions and, possibly, their athletic capacity.
Objective of the Research
This study aims to examine the long-term outcomes (in terms of physique and potential athletic performance) of prematurity and dysmaturity (born at term but showing some signs of prematurity) in foals.
The researchers specifically hypothesized that horses born prematurely or dysmaturely might experience shorter stature and altered body ratios in adulthood, resembling human conditions.
Methodology
The study investigated the skeletal proportions of horses with a history of gestational immaturity. These horses were identified through a series of veterinary and breeder records.
For comparison, the study also examined unaffected horses that were closely related to the horses with this history (e.g., their parents or siblings).
Measurements of the horses were taken from conformation photographs. These measurements were then transformed into indices which were used to assess the horses’ conformation.
The researchers carried out a principal component analysis, which showed that the first two principal components account for almost half of the total conformational variation of the horses’ external features.
Findings
The study found significant effects of gestational immaturity on horse conformation, with prematurely born horses being more affected than dysmature ones.
According to the mean values for the four dominant indices, the study revealed that premature and dysmature horses have significantly lower distal limb to body length relationships than unaffected controls.
Implications
The observed differences imply that gestational immaturity can influence the anatomical ratios of horses at maturity.
The findings also suggest that in conjunction with orthopedic problems stemming from incomplete ossification, gestational immaturity might further affect the long-term athletic potential of horses.
Cite This Article
APA
Clothier J, Small A, Hinch G, Brown WY.
(2020).
Prematurity and Dysmaturity Are Associated With Reduced Height and Shorter Distal Limb Length in Horses.
J Equine Vet Sci, 91, 103129.
https://doi.org/10.1016/j.jevs.2020.103129
Agriculture and Food, CSIRO, New England Highway, Armidale, New South Wales, Australia; Canine and Equine Research Group, University of New England, Armidale, New South Wales, Australia; School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia. Electronic address: jane.clothier@une.edu.au.
Small, Alison
Canine and Equine Research Group, University of New England, Armidale, New South Wales, Australia.
Hinch, Geoff
School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia.
Brown, Wendy Y
Canine and Equine Research Group, University of New England, Armidale, New South Wales, Australia; School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia.