An investigation into progeny performance results in dual hemisphere stallions

The Thoroughbred has been intensely selected for speed and performance since its development over 300 years ago. The concept of shuttle stallions was introduced in 1990 in order to introduce novel bloodlines in Australia and maintain genetic diversity in the Thoroughbred population. However Thoroughbred racing varies in different racing regions with Australia requiring faster and more precocious 2 year old horses suitable for sprint races while Great Britain and Ireland has a higher demand for a horse more suited to middle distance races. The aim of this study was to test the hypothesis that environment influences progeny performance results in shuttle stallions. Thirteen stallions were identified as having shuttled between Australia and Great Britain in the 2007 and 2008 breeding seasons. This study evaluated the difference in performance among progeny of shuttle stallions that had horses racing in the Northern Hemisphere (n = 926) and Southern Hemisphere (n = 483). Overall horses in Great Britain and Ireland had a higher number of starts, wins and places than Australian progeny. They also ran in longer distance races than Australian progeny. When looked at per stallion, progeny sired by certain sires had a higher proportion of wins in Great Britain and Ireland. This study has shown that progeny performance results are influenced by the environment. Progeny of certain stallions are more likely to be suited to racing distances in Great Britain and Ireland. Stallions that are to shuttle to Australia should meet the market requirements of that country and produce progeny that are suited to that