Digging Deeper into Breeders' Cup Lasix Study

A follow-up look at some of the racing statistics of juveniles involved in the furosemide observational study results released Dec. 16 by Breeders' Cup from this year's World Championships and two California-bred stakes races for 2-year-olds at Santa Anita Park provides some interesting additional information.

The observational study found that 2-year-olds racing without race-day furosemide (commonly called Lasix or Salix) at the 2013 Breeders' Cup—the four World Championship races plus the Juvenile Turf Sprint—had fewer and less severe instances of exercise-induced pulmonary hemorrhage than juveniles who raced with the diuretic that same weekend at Santa Anita in a pair of stakes for California-breds.

In the voluntary study that saw connections of 70.5% of the horses participate, 71% of the horses who raced with Salix (10 of 14) were observed to have some level of EIPH while just 37% of the non-treated horses (15 of 41) showed some level of EIPH.

The severity of EIPH was determined on a four-grade (four being most severe) scale. The Salix-treated horses again showed significantly higher numbers of severe bleeding, as 36% (five of 14) showed grade three or grade four EIPH, compared with only 7% (three of 41) at those grade levels in the non-treated group.

Some additional information through research of past performances going into those races follows.

• The juveniles in the Cal-bred races were, on average, more experienced than the 2-year-olds in the Breeders' Cup races, where Lasix was prohibited. The 19 Cal-breds who started in the two races entered with an average of 4.1 previous starts while the 59 Breeders' Cup starters averaged 3.6 previous starts.

• Of the 78 previous starts made by the Cal-breds, 74 of those efforts included the administration of race-day Lasix (94.9%). Only two of the 19 starters (10.5%) previously had ever started without it. All 19 started on Lasix in the two Nov. 1 stakes races.

• Of the 59 starters in the five Breeders' Cup races for 2-year-olds that prohibited race-day Lasix, 19 (32.2%) had previously raced without the diuretic. Of the 212 previous starts of this group, 157 (74%) were made with Lasix.

• The six top-three placings in the Cal-bred races were all secured by horses who had exclusively started on Lasix. Eight of the 15 (53.3%) placings in the five Breeders' Cup juvenile races were secured by horses who had previously raced without furosemide.

• European-trained horses in turf races accounted for three of those Breeders' Cup placings by starters who previously had made at least one start without Lasix: Chriselliam, winner of the Breeders' Cup Juvenile Fillies Turf (gr. IT); and Outstrip and Giovanni Boldini, respective winner and runner-up in the Juvenile Turf (gr. IT).

• Five U.S.-trained horses to previously make starts without Lasix earned placings in the Breeders' Cup juvenile races, including Richies Party Girl, winner of the Juvenile Turf Sprint; Testa Rossi and Colonel Joan, second and third in Juvenile Fillies Turf; and Ria Antonia and Rosalind, first and third in Juvenile Fillies (gr. I).

• The only Breeders' Cup juvenile race that did not see a starter who previously raced without Lasix finish in the top three was the Juvenile, where all 13 starters had exclusively raced on Lasix.

• The 19 Cal-bred starters entered with 22 previous wins in their previous 42 starts while the 59 Breeders' Cup juveniles entered with 95 wins in their previous 212 starts.

While the study was observational as opposed to scientific—and the sample size small—researchers observed a statistically significant higher percentage of EIPH frequency, and severity, in horses treated with furosemide Nov. 1 at Santa Anita compared with those who raced without it that weekend at the track. 

Furosemide is the only race-day medication permitted in the majority of North American racing states and it is used to treat EIPH, which at its most severe grade can include bleeding through the nostrils. Breeders' Cup has prohibited race-day Salix use in juvenile races in the two most recent World Championships.