Growth and development of Thoroughbred horses
P. J. Huntington
A C , C. G. Brown-Douglas A and J. D. Pagan B
+ Author Affiliations
- Author Affiliations
A Kentucky Equine Research, 2/35 Dunlop Road, Mulgrave, Vic. 3170, Australia.
B Kentucky Equine Research, 3910 Delaney Ferry Road, Versailles, KY 40383, USA.
C Corresponding author. Email: phuntington@ker.com
Animal Production Science 60(18) 2093-2102 https://doi.org/10.1071/AN19629
Submitted: 31 October 2019 Accepted: 12 October 2020 Published: 10 November 2020
Abstract
Research into the growth and development of Thoroughbreds managed on commercial breeding farms is reviewed in this paper. As horses are not meat producing animals, less research has been performed quantifying growth, muscle and bone development than with other production animals. However, variations in growth and development are linked with both value and wastage in young Thoroughbred horses, and can have a long-term impact on racing performance. In Thoroughbred horses, the breeder aims for optimum, or consistent, growth rather than maximum growth. Factors affecting equine growth including environment, nutrition, season and management are discussed in sections covering conception to weaning, weanling to yearling and yearling to 2 years old when horses are nearly fully grown and racing begins. The importance of reference curves for different ages, sex and locations is highlighted. While average daily gain (ADG) declines as the foal gets older, there are seasonal and management influences to consider. Month of birth has an influence on both birthweight and the expected ADG at different ages, which are believed to be related to ambient temperatures and pasture availability for the mare and growing horse. Weaning leads to a growth setback and ADG declines through winter, but increases in spring for the yearling as temperatures and pasture quality and quantity increase. Management factors such as yearling sale preparation are associated with an increase in growth rate, with gains of over 1 kg/day common during the yearling sales preparation process of 6–12 weeks. ‘Home-bred’ horses that do not go to a yearling sale grow at a slower rate but will reach the same endpoint in mature size. Growth of Thoroughbreds is influenced by country, and regions within a country, related to genetics, climate, management practices, market preferences and sale timing. More research is needed into factors affecting growth and development of Thoroughbred horses on commercial farms and the influence differing rates of growth and development have on wastage (such as developmental orthopaedic disease) and commercial outcomes such as yearling sale results and, ultimately, racing performance.
Keywords: growth regulators, horses.
References
Barneveld AR, van Weeren R (1999) Conclusions regarding the influence of exercise on the development of the equine musculoskeletal system with special reference to osteochondrosis. Equine Veterinary Journal 31, 112–119.| Conclusions regarding the influence of exercise on the development of the equine musculoskeletal system with special reference to osteochondrosis.Crossref | GoogleScholarGoogle Scholar |
Brown-Douglas CG, Pagan JD (2009) Body weight, wither height and growth rates in Thoroughbreds raised in America, England, Australia, New Zealand and India. In ‘Advances in equine nutrition IV’. (Ed JD Pagan) pp. 213–220. (Nottingham University Press: Nottingham, UK)
Brown-Douglas CG, Firth EC, Parkinson TP, Fennessy PF (2004) Onset of puberty in pasture-raised Thoroughbreds born in spring and autumn. Equine Veterinary Journal 36, 499–504.
| Onset of puberty in pasture-raised Thoroughbreds born in spring and autumn.Crossref | GoogleScholarGoogle Scholar | 15460074PubMed |
Brown-Douglas CG, Parkinson TJ, Firth EC, Fennessy PF (2005) Body weights and growth rates of spring- and autumn-born Thoroughbred horses raised on pasture. New Zealand Veterinary Journal 53, 326–331.
| Body weights and growth rates of spring- and autumn-born Thoroughbred horses raised on pasture.Crossref | GoogleScholarGoogle Scholar | 16220125PubMed |
Brown-Douglas CG, Pagan JD, Koch A, Caddel S (2007) The relationship between size at yearling sale, sale price and future racing performance in Kentucky Thoroughbreds. Proceedings of Equine Science Society Symposium 20, 153–154.
Brown-Douglas CG, Pagan JD, Stromberg AJ (2009) Thoroughbred growth and future racing performance. In ‘Advances in equine nutrition IV’. (Ed JD Pagan) pp. 231–245. (Nottingham University Press: Nottingham, UK)
Carroll CL, Huntington PJ (1988) Body condition scoring and weight estimation of horses. Equine Veterinary Journal 20, 41–45.
| Body condition scoring and weight estimation of horses.Crossref | GoogleScholarGoogle Scholar | 3366105PubMed |
Chin YY, Roca Fraga FJ, Back PJ, Gee EK, Rogers CW (2020) The dynamics of energy supply and demand of foaling mares managed at pasture: a deterministic modelling approach. Animal Production Science.
| The dynamics of energy supply and demand of foaling mares managed at pasture: a deterministic modelling approach.Crossref | GoogleScholarGoogle Scholar |
Cymbaluk NF, Christison GI (1989) Effects of diet and climate on growing horses Journal of Animal Science 67, 48–59.
| Effects of diet and climate on growing horsesCrossref | GoogleScholarGoogle Scholar | 2925552PubMed |
Elliott C, Morton J, Chopin J (2009) Factors affecting foal birth weight in Thoroughbred horses. Theriogenology 71, 683–689.
| Factors affecting foal birth weight in Thoroughbred horses.Crossref | GoogleScholarGoogle Scholar | 18980778PubMed |
Firth EC, Rogers CW, van Weeren PR, Barneveld A, McIlwraith CW, Kawcak CE, Goodship AE, Smith RK (2011) Mild exercise early in life produces changes in bone size and strength but not density in proximal phalangeal, third metacarpal and third carpal bones of foals. Veterinary Journal 190, 383–389.
| Mild exercise early in life produces changes in bone size and strength but not density in proximal phalangeal, third metacarpal and third carpal bones of foals.Crossref | GoogleScholarGoogle Scholar |
Firth EC, Rogers CW, van Weeren PR, Barneveld A, McIlwraith CW, Kawcak CE, Goodship AE, Smith RK (2012) The effect of previous conditioning exercise on diaphyseal and metaphyseal bone to imposition and withdrawal of training in young Thoroughbred horses. Veterinary Journal 192, 34–40.
| The effect of previous conditioning exercise on diaphyseal and metaphyseal bone to imposition and withdrawal of training in young Thoroughbred horses.Crossref | GoogleScholarGoogle Scholar |
Fradinho MJ, Correia MJ, Grácio V, Bliebernicht M, Farrim A, Mateus L, Martin-Rosset W, Bessa RJB, Caldeira RM, Ferreira-Dias G (2014) Effects of body condition and leptin on the reproductive performance of Lusitano mares on extensive systems. Theriogenology 81, 1214–1222.
| Effects of body condition and leptin on the reproductive performance of Lusitano mares on extensive systems.Crossref | GoogleScholarGoogle Scholar | 24613603PubMed |
Frape D (1998) ‘Equine nutrition and feeding.’ 2nd edn. (Blackwell Science: Oxford, UK)
Grace ND, Pearce SG, Firth EC, Fennessy PF (1999) Concentrations of macro- and micro-elements in the milk of pasture-fed Thoroughbred mares. Australian Veterinary Journal 77, 177–180.
| Concentrations of macro- and micro-elements in the milk of pasture-fed Thoroughbred mares.Crossref | GoogleScholarGoogle Scholar | 10197247PubMed |
Grace ND, Gee EK, Firth EC, Shaw HL (2002) Digestible energy intake, dry matter digestibility and mineral status of grazing Thoroughbred yearlings. New Zealand Veterinary Journal 50, 63–69.
Green DA (1969) A study of growth rate in Thoroughbred foals. The British Veterinary Journal 125, 539–546.
| A study of growth rate in Thoroughbred foals.Crossref | GoogleScholarGoogle Scholar | 5394073PubMed |
Green DA (1976) Growth rate in Thoroughbred yearlings and two year olds. Equine Veterinary Journal 8, 133–134.
| Growth rate in Thoroughbred yearlings and two year olds.Crossref | GoogleScholarGoogle Scholar | 954724PubMed |
Henneke DR, Potter GD, Kreider JL (1981) A condition score relationship to body fat content of mares during gestation and lactation. In ‘Proceedings of the 7th equine nutrition and physiology symposium’. pp. 105–110. (Equine Nutrition and Physiology Society: Airlie, VA, USA)
Hintz HF, Schryver HF, Lowe JE (1976) Delayed growth response and limb conformation in young horses. In ‘Proceedings of the Cornell nutrition conference’. pp. 94–96. (Cornell University: Ithaca, NY, USA)
Hintz HF, Hintz RL, van Vleck LD (1979) Growth rate of Thoroughbreds: effect of age of dam, year and month of birth, and sex of foal. Journal of Animal Science 48, 480–487.
| Growth rate of Thoroughbreds: effect of age of dam, year and month of birth, and sex of foal.Crossref | GoogleScholarGoogle Scholar | 575130PubMed |
Hunt WF, Thomas VG, Stiefel W (1999) Analysis of video recorded images to determine linear and angular dimensions in the growing horse. Equine Veterinary Journal 31, 402–410.
| Analysis of video recorded images to determine linear and angular dimensions in the growing horse.Crossref | GoogleScholarGoogle Scholar | 10505956PubMed |
Huntington PJ, Brown-Douglas CG, Pagan JD (2007) Growth of Australian Thoroughbreds compared with horses in New Zealand, America, England and India. Australian Equine Veterinarian 26, 80–92.
Hurtig MB, Pool RR (1996) Pathogenesis of equine osteochondrosis. In ‘Joint disease in the horse’. (Eds CW McIlwraith, GW Trotter) pp. 335–358. (Saunders: Philadelphia, PA, USA)
Jelan ZA, Jeffcott LB, Lundeheim N, Osborne M (1996) Growth rates in Thoroughbred foals. Pferdeheilkunde 12, 291–295.
| Growth rates in Thoroughbred foals.Crossref | GoogleScholarGoogle Scholar |
Kocher A, Staniar WB (2013) The pattern of thoroughbred growth is affected by a foal’s birthdate. Livestock Science 154, 204–214.
| The pattern of thoroughbred growth is affected by a foal’s birthdate.Crossref | GoogleScholarGoogle Scholar |
Lawrence LA (2005) Principles of bone development in horses. In ‘Advances in equine nutrition III’. pp. 289–294. (Nottingham University Press: Nottingham, UK)
Lepeule J, Bareille N, Robert C, Valette J-P, Jacquet S, Blanchard G, Denoix JM, Seegers H (2013) Association of growth, feeding practices and exercise conditions with the severity of the osteoarticular status of limbs in French foals. Veterinary Journal 197, 65–71.
| Association of growth, feeding practices and exercise conditions with the severity of the osteoarticular status of limbs in French foals.Crossref | GoogleScholarGoogle Scholar |
Lewis LD (1980) Nutrition of the broodmare and growing horse and its role in epiphysitis. Proceedings of the 26th Annual Convention of the American Association of Equine Practitioners 25, 269–296.
Martin-Rosset W (2005) Growth and development in the equine. In ‘The growing horse: nutrition and prevention of growth disorders’. EAAP publication no. 114. (Eds V Juliand, W Martin-Rosset) pp. 15–50. (Wageningen Academic: Wageningen, The Netherlands)
Mawdsley A, Kelly EP, Smith FH, Brophy PO (1996) Linear assessment of the Thoroughbred horse: an approach to conformation evaluation. Equine Veterinary Journal 28, 461–467.
| Linear assessment of the Thoroughbred horse: an approach to conformation evaluation.Crossref | GoogleScholarGoogle Scholar | 9049495PubMed |
McCarthy D, Mitchell J (1974) A study of growth rate in Thoroughbred foals and yearlings. Israel Journal of Agricultural Research 13, 111–117.
Morel PC, Bokor A, Rogers CW, Firth EC (2007) Growth curves from birth to weaning for Thoroughbred foals raised on pasture. New Zealand Veterinary Journal 55, 319–325.
| Growth curves from birth to weaning for Thoroughbred foals raised on pasture.Crossref | GoogleScholarGoogle Scholar | 18059651PubMed |
Nash DG, Avery A, Dempsey W, Nash G (2001) Growth and development of young Thoroughbred horses on temperate Australian pastures. In ‘Proceedings of the 17th equine nutrition and physiology symposium’. pp. 196–198. (Equine Nutrition and Physiology Society: Lexington, KY, USA)
Nogueira GP, Barnabe RC, Verreschi IT (1997) Puberty and growth rate in Thoroughbred fillies. Theriogenology 48, 581–588.
| Puberty and growth rate in Thoroughbred fillies.Crossref | GoogleScholarGoogle Scholar | 16728154PubMed |
National Research Council (NRC) (2007) ‘Nutrient requirements of horses.’ 6th edn. (National Academies Press: Washington, DC, USA)
Onoda T, Yamamoto R, Sawamura K, Murase H, Nambo Y, Inoue Y, Matsui A, Miyake T, Hirai N (2014) An approach of estimating individual growth curves for young Thoroughbred horses based on their birthdays. Journal of Equine Science 25, 29–35.
| An approach of estimating individual growth curves for young Thoroughbred horses based on their birthdays.Crossref | GoogleScholarGoogle Scholar | 25013356PubMed |
Orton RK, Hume ID, Leng RA (1985) Effects of level of dietary protein and exercise on growth rates of horses. Equine Veterinary Journal 17, 381–385.
| Effects of level of dietary protein and exercise on growth rates of horses.Crossref | GoogleScholarGoogle Scholar | 4054089PubMed |
Owen JM (1975) Abnormal flexion of the corono-pedal joint or ‘contracted tendons’ in unweaned foals. Equine Veterinary Journal 7, 40–45.
| Abnormal flexion of the corono-pedal joint or ‘contracted tendons’ in unweaned foals.Crossref | GoogleScholarGoogle Scholar | 1116494PubMed |
Pagan JD (1998) The incidence of developmental orthopaedic disease (DOD) on a Kentucky Thoroughbred farm. In ‘Advances in equine nutrition I’. (Ed. JD Pagan) pp. 469–475. (Nottingham University Press: Nottingham, UK)
Pagan JD (2005a) Managing growth for different commercial end points. In ‘Advances in equine nutrition III’. (Ed JD Pagan) pp. 319–326. (Nottingham University Press: Nottingham, UK)
Pagan JD (2005b) The role of nutrition in the management of developmental orthopaedic disease. In ‘Advances in equine nutrition III’. (Ed. JD Pagan) pp. 417–431. (Nottingham University Press: Nottingham, UK)
Pagan JD, Jackson SG, Caddel S (1996) A summary of growth rates of Thoroughbreds in Kentucky. Pferdeheilkunde 12, 285–289.
| A summary of growth rates of Thoroughbreds in Kentucky.Crossref | GoogleScholarGoogle Scholar |
Pagan JD, Koch A, Caddel S, Nash D (2005) Size of Thoroughbred yearlings presented for auction at Keeneland sales affects selling price. Proceedings of the Equine Science Society Symposium 19, 224–225.
Pagan JD, Brown-Douglas CG, Caddel S (2009) Body weight and condition of Kentucky Thoroughbred mares and their foals as influenced by month of foaling, season and gender. In ‘Advances in equine nutrition IV’. (Ed. JD Pagan) pp. 137–145. (Nottingham University Press: Nottingham, UK)
Platt H (1978) Growth and maturity in the equine foetus. Journal of the Royal Society of Medicine 71, 658–661.
| Growth and maturity in the equine foetus.Crossref | GoogleScholarGoogle Scholar | 712744PubMed |
Raub RH, Jackson SG, Baker JP (1989) The effect of exercise on bone growth and development in weanling horses. Journal of Animal Science 67, 2508–2514.
| The effect of exercise on bone growth and development in weanling horses.Crossref | GoogleScholarGoogle Scholar | 2808156PubMed |
Reynolds LP, Borowicz PP, Caton JS, Crouse MS, Dahlen CR, Ward AK (2019) Developmental programming of fetal growth and development. The Veterinary Clinics of North America. Food Animal Practice 35, 229–247.
| Developmental programming of fetal growth and development.Crossref | GoogleScholarGoogle Scholar | 31103178PubMed |
Rogers CW, Firth EC, McIlwraith CW, Barneveld A, Goodship AE, Kawcak CE, Smith RK, van Weeren PR (2008) Evaluation of a new strategy to modulate skeletal development in Thoroughbred performance horses by imposing track-based exercise during growth. Equine Veterinary Journal 40, 111–118.
| Evaluation of a new strategy to modulate skeletal development in Thoroughbred performance horses by imposing track-based exercise during growth.Crossref | GoogleScholarGoogle Scholar | 18093894PubMed |
Rogers CW, Gee EK, Bolwell CF (2016) Reproductive production constraints within the New Zealand racing industry. Proceedings of the New Zealand Society of Animal Production 76, 146–150.
Rooney JR (1984) Weather factors and the growth of young Thoroughbred horses. Journal of Equine Veterinary Science 4, 106–107.
| Weather factors and the growth of young Thoroughbred horses.Crossref | GoogleScholarGoogle Scholar |
Savage CJ, McCarthy RN, Jeffcott LB (1993) Effects of dietary energy and protein on induction of dyschondroplasia in foals. Equine Veterinary Journal 25, 74–79.
| Effects of dietary energy and protein on induction of dyschondroplasia in foals.Crossref | GoogleScholarGoogle Scholar |
Smith AM, Splan RK (2005) Correlations between yearling body measurements and career racing performance. In ‘Proceedings of the 19th Equine Science Society Symposium’. pp. 222–223. (Equine Science Society: Tucson, AZ, USA)
Staniar WB, Kronfeld DS, Treiber KH, Splan RK, Harris PA (2004a) Growth rate consists of baseline and systematic deviation components in Thoroughbreds. Journal of Animal Science 82, 1007–1015.
| Growth rate consists of baseline and systematic deviation components in Thoroughbreds.Crossref | GoogleScholarGoogle Scholar | 15080321PubMed |
Staniar WB, Kronfeld DS, Hoffman RM, Wilson JA, Harris PA (2004b) Weight prediction from linear measures of growing Thoroughbreds. Equine Veterinary Journal 36, 149–154.
| Weight prediction from linear measures of growing Thoroughbreds.Crossref | GoogleScholarGoogle Scholar | 15038438PubMed |
Takahashi Y, Takahashi T (2017) Seasonal fluctuations in body weight during growth of Thoroughbred racehorses during their athletic career. BMC Veterinary Research 13, 257
| Seasonal fluctuations in body weight during growth of Thoroughbred racehorses during their athletic career.Crossref | GoogleScholarGoogle Scholar | 28821254PubMed |
Tanner JM (1981) Growth and maturation during adolescence. Nutrition Reviews 39, 43–55.
| Growth and maturation during adolescence.Crossref | GoogleScholarGoogle Scholar | 7010232PubMed |
Thompson KN (1995) Skeletal growth rates of weanling and yearling Thoroughbred horses. Journal of Animal Science 73, 2513–2517.
| Skeletal growth rates of weanling and yearling Thoroughbred horses.Crossref | GoogleScholarGoogle Scholar | 8582838PubMed |
Thompson KN, Smith BP (1994) Skeletal growth patterns of Thoroughbred horses. Journal of Equine Veterinary Science 14, 148–151.
| Skeletal growth patterns of Thoroughbred horses.Crossref | GoogleScholarGoogle Scholar |
Thompson KN, Jackson SG, Rooney JR (1988) The effect of above average weight gains on the incidence of radiographic bone aberrations and epiphysitis in growing horses. Journal of Equine Veterinary Science 8, 383–385.
| The effect of above average weight gains on the incidence of radiographic bone aberrations and epiphysitis in growing horses.Crossref | GoogleScholarGoogle Scholar |
Valette JP, Robert C, Toquet MP, Denoix JM, Fortier G (2007) Evolution of some biochemical markers of growth in relation to osteoarticular status in young horses: results of a longitudinal study in three breeds. Equine Comparitive Exercise Physiology 4, 23–29.
| Evolution of some biochemical markers of growth in relation to osteoarticular status in young horses: results of a longitudinal study in three breeds.Crossref | GoogleScholarGoogle Scholar |
Valette JP, Robert C, Denoix JM (2008) Use of linear and non-linear functions to describe the growth of young sport- and race-horses born in Normandy. Animal 2, 560–565.
| Use of linear and non-linear functions to describe the growth of young sport- and race-horses born in Normandy.Crossref | GoogleScholarGoogle Scholar | 22443570PubMed |
Waldron K, Rogers CW, Gee EK, Bolwell CF (2011) Production variables influencing the auction sales price of New Zealand Thoroughbred yearlings. Proceedings of the New Zealand Society of Animal Production 71, 92–5.
Warren LK, Lawrence LM, Parker AL, Barnes T, Griffin AS (1998) The effect of weaning age on foal growth and radiographic bone density. Journal of Equine Veterinary Science 18, 335–342.
| The effect of weaning age on foal growth and radiographic bone density.Crossref | GoogleScholarGoogle Scholar |
Wilsher S, Allen WR (2003) The effects of maternal age and parity on placental and foetal development in the mare. Equine Veterinary Journal 35, 476–483.
| The effects of maternal age and parity on placental and foetal development in the mare.Crossref | GoogleScholarGoogle Scholar | 12875326PubMed |
