Profiling the reproductive life of the New Zealand Thoroughbred broodmare

Abstract

The Thoroughbred stud book is New Zealands largest stud book, however the breeding population has decreased in the past years. In this study the stud book career of 1998/1999 season sired filly foals of three stallions per sire category (Cheap <$5000, Medium $5001-$10.000, Expensive >$10.000 and Shuttle (both hemispheres) was identified, including racing, breeding and sales records. The same was procedure was followed for the dams and granddams of these foals. Proven, expensive, stallions cover most mares per stallion. Foals of expensive and shuttle stallions behave differently in the population than foals of cheap and medium stallions. Foals of expensive sires had a higher commercial value, and breeders seemed to be more intent on reclaiming part of their initial investment. A greater proportion of expensive sired foals was sold on the Premier Yearling Sale, exported, raced and entered the breeding population. The same effect was observed for shuttle sired foals, although there did seem to be a stricter selection for shuttle sired foals to enter the breeding herd. Foals of cheap stallions started breeding at a later age and had a lower parity. The proportion of racing broodmares decreased in older generations. The parity of granddams was lower than the parity of the 1999 foals and dam. However, records seemed to become more unreliable when going back further in time. A smaller proportion expensive sired broodmares raced, indicating a stricter selection on racing performance for cheap and medium sired broodmares. Cheap sires seemed to disappear from the gene pool over time, with granddams being sired mainly by medium and expensive stallions in an equal measure. Breeders were positively influenced by mare fertility in the decision whether to cover a mare again. This effect was strongest in the dams.