Pagan Shares Data on Thoroughbred Growth, Performance

What does the birth month and weight of a Thoroughbred foal have to do with its ability to perform on the racetrack? Dr. Joe Pagan, president and founder of Kentucky Equine Research, discussed the topic Dec. 8 at Spy Coast Farm's equine education center in Lexington.

Pagan formed KER in 1988 to more closely study equine nutrition and sports medicine. Since then, he has conducted several studies on Thoroughbred foals, including skeletal soundness and seasonal effect (what month foals were born in and how it effects weight and bone growth).

"We started to accumulate so much data that we developed a software program that will allow us to handle it called Gro-Trac," Pagan said. "This allows us to put all the information into a single program, present it back to the breeder, and use reference curves."

Presented by Hallway Feeds, Pagan's presentation titled "Thoroughbred Growth and Performance: An International Perspective," surrounded a recent study where he compared Central Kentucky Thoroughbred growth against that of European Thoroughbred growth. He used a slideshow with figures to illustrate the various topics.

The study in Kentucky was conducted during 2014-18 and included 13 different farms, 1,403 foals, and 41 foal crops.

From this group, Pagan collected growth data that included birth weight and monthly measurements (body weight as well as wither height). He also collected data that included looking at how much the foals sold for at auction and if they were successful on the track.

"We have growth data that is collected on a monthly basis as well as performance data, how well they can sell, how well did they run," Pagan said. "We also did the same type of study with a group of horses in England."

The data collected from Europe was during 2005-2019, and included information from six farms, 1,716 foals, and 48 foal crops.

For purposes of confidentiality, none of the farms that were used to collect data were named in the study. Pagan described the farms as a "biased demographic" as this data does not necessarily apply to the overall population of Thoroughbreds. He added that the foals studied in both locations were "elite populations" that may not be representative of foals produced in locations that were not as high quality.

Pagan noted that data collected in Kentucky was more uniform than the data that came from the U.K. For the Kentucky study, the same equipment and specialists were used to collect the exact weights of foals whereas the U.K. study relied on information collected by the individual farms that was then sent to Pagan.

The study found that in Kentucky, foals have a higher birth weight than foals in the U.K. The average birth weight for Kentucky foals was 124.7 pounds while the average U.K. foal weighed in at 121.7 pounds.

From the larger group, Pagan evaluated sub-populations of the Kentucky foals, delving into the month the foal was born, incidents of skeletal disease, parity (maiden or multiparous mares, which are mares that have had multiple foals), as well as their performance on the track (starters, winners, stakes winners, graded stakes winners). 

His research into the skeletal aspect was mainly focused around the development of osteochondritis dissecans (OCD), which is loose cartilage or bone fragments in joints.

"For skeletal disease, though we got radiographic survey data from the farms for this, it took us massive amounts of time to tease through all of that data to pull out the incidence of specific problems radiographically and the incidence of surgery," Pagan said.

OCD in horses can develop for a number of different reasons, including heritability, conformation (influenced by exercise and confinement), nutrition (too little, too much), body weight, and growth rate. 

One finding was that maiden foals (the first foal out of a mare) are significantly smaller than foals out of multiparous mares. The median weight for maiden foals is 113.8 pounds while the median weight for multiparous foals is 128.5 pounds.

There is also evidence to suggest that foals out of maiden mares have 35% less total OCD than foals out of multiparous mares, Pagan said.

The month a foal is born in did show a strong correlation to size. Essentially, foals born in February are smaller than those born in April or May. Research also suggests that a higher body weight earlier on in the horse's life could result in more cases of OCD. 

Pagan also mentioned that if a foal is heavier than 139 pounds at birth, they are two times more likely to have surgery for OCD and are one-third as likely to become stakes winners.

Other statistics evaluated sales ring success and on-track performance. When comparing the location of OCD surgeries, those performed upon lesions in the hock did not affect sales and racing performance, while those performed upon lesions occurring in the stifle did have an adverse effect.

The presentation came to a close as Pagan discussed how Kentucky farms and breeders should consider managing foals with a larger birth weight.

"I would maintain that if you have foals that are larger than 140 pounds at birth, they are at higher risk than foals that are born smaller than that," he said. "How do you manage it? Measure them first. Find out, 'What are these weights?' Identify them as high risk.

"What I think this data conclusively shows is that small foals are more resilient than larger foals... They are less likely to get OCD. These larger foals, you need to pay more attention to."

He also offered advice on how to address the issue before a foal even hits the ground.

"I think in terms of a management tool, appreciate how important grass is in Kentucky and how important it is to a lactating mare's nutrient intake," Pagan said. "Probably (we need to be) more cognizant of how (pasture contributes) compared to the hard feed you're using and whether we can adjust the extra calories we're giving to these mares to reduce this type of excess energy intake."