Equine growth data

Nutrionist Joe Pagan of Kentucky Equine Research has an extensive data collection tracking thoroughbred growth. We report on his newest, ground-breaking findings

BIG DATA, its use, its understanding and its application, coupled with scientific knowledge, has become the vital way forward for all industries.

Far ahead in the field of bloodstock and thoroughbred nutrition is Joe Pagan of Kentucky Equine Research (KER), who has been collecting and analysing data alongside the US-based feed company Hallway Feeds for 30 years and the UK’s Saracen Feeds for 21.

This work, via regular weighing of foals from birth through to maturity, has greatly increased the understanding of thoroughbred growth, and has allowed Pagan to determine some informative findings.

“We started weighing horses very early on,” reported Pagan at the Saracensponsored Thoroughbred Forum held in June at Newbury and Newmarket. “We felt that weight and growth rate had an effect on skeletal soundness, and we’ve been looking at it a long time.

“From a paper published in 1996 on a growth study in Kentucky we found even back then that heavier foals, young foals of around 25 days of age, had more hock and stifle OCD issues.

“Steve Caddel at Hallway started a weighing service going around the studs once a month, weighing the foals, measuring their height and condition scoring the horses. If the foal was by her side he’d also weigh the lactating mare, and he has done that for the last 30 years.

“We now have a database of 47,000 foals that we’ve weighed and measured.”

The results produced some definitive early findings (see tables in pdf).

“We published some early data on just regular growth rate of foals in Kentucky and we found something really surprising – average daily gain decreases with age until the horses get to be about 11 to 15 months of age.

“Then in April every single yearling, regardless of when it was born, starts to grow fast again; that’s when our grass comes on.”

KER has been measuring thoroughbred growth all over the world – England, Australia, India, New Zealand, and it has been found that where foals are located makes a big difference to how they grow.

When this big data collection indeed started getting very big, Pagan worked on a software programme to handle the content – launched in 2000-2001 this became known as Gro Trac, a straightforward recording and analytical programme which can be used in-house by both by Pagan and his team for analytics, and on farm by breeders and stud staff for recording purposes.

“Gro Trac allows us to summarise the data and, more importantly, compare how foals are growing to another population of foals,” says Pagan.

To do this, Pagan made use of percentiles, working out where the individual fitted into the normal distribution of growth.

The team used data from a study called “Relationship between Foal Body Weight, withers height and OCD, Sales and Racing Performance in Kentucky Thoroughbred Foals”alongside data combined with similar data collected in Europe by Saracen’s clients.

The team then divided the data into a number of sub populations: 1. By performance – starters, winners, stakes winners, graded stakes are millionaires 2. By month of birth 3. By parity – whether the foals were out of maiden or multiparous mares. 4. By skeletal disease – no OCD, OCD survey and surgery split via fetlock, hocks and stifles as well as any other issues such as fragments and chips and cysts.

We run through the first four findings in this issue and the last, point 4, in the next’s month’s edition.

Data findings ... see the pdf for tables

Birth weights and parody

The median birth weight for all foals in the study is 55kgs and in the UK the median is a little higher at 56kgs.

A big weight difference, however, was found between foals born from maiden mares and those from mares who have had a number of foals.

“The thing that we found in the UK and in the US is parody makes a huge difference,” reports Pagan.

The average weight of foals from maiden mares is 8kg lighter than those from multiparous mares, and this difference was found in all geographical locations.

The median weight from UK maiden mares was 49kg, in the US this icreased slightly to 51kg and dropped to 47.5kg in Australia.

For the multiparous mare in the UK the median found was 57kg, it was 58kg in the US and 56kg in Australia.

Stakes winners and birth weights

As can be seen in the scatter graph (see table overleaf) few UK foals born above 64kg went onto become stakes winners, and none of the heavy foals in the US achvied that target.

In the UK of the lighter foals, none of the five per cent of those smaller, foals, became stakes winners.

In the US, 13 per cent of foals were born above 64kg, but of these only two per cent won at stakes level.

Looking at the non-maiden mares (middle table), no foal born below 44kg, bar a couple in Australia, were stakes winners.

Foals born between 44kg and 64kg provides the zone in which most stakes winners, from both maiden and multiparous mares, are born.

Birth weights: sales prices and earnings

Here the results narrow further again from the stakes winning data. In the UK only three per cent of the top 10 per cent of sales horses weighed more than 64kg as foals, and only two per cent below 44kg.

In the UK, 95 per cent of foals of the top-earning foals weighed between 44 kg and 64kg. Foals born in the band between 44kg and 66kg have the best results Difference in body weight percentile of UK and US young horses

Pagan says: “There is a difference in the size of UK thoroughbreds versus US, and that is the finding that I went ‘Wow!’; it is a very interesting difference”

The graph (opposite) shows clearly that the growth rates in the US and the UK are very different.

The majority of foals in both regions start at the same size in the 60th percentile and the US horses continue along that trajectory; the UK thoroughbreds get relatively smaller as they age.

Yearlings sales and percentiles

In the US, 50 per cent of the foals in the top 10 per cent of yearlings sold (the ‘elite’ yearlings) were in the fourth weight quartile (see opposite, blue) with another 25 per cent in the third quartile. It means that 75 per cent of the top yearling sales were above the median body weight.

In the UK, most of the top-priced yearlings were found in the second quartile (red). Conversely to the US the fourth quartile, the heaviest yearlings, only produced 12 per cent of the top 10 per cent of the sale yearlings.

The UK sales market essentially discriminates against big yearlings, while in the US big yearlings are more popular in the sale ring. The data proves that heavy yearlings are not popular in the UK, but it is vice versa in the US

Does the sales data correlate with stakes race winners?

In the US, 44 per cent of the horses who won stakes races came from the fourth weight quartile (see middle table, blue graph), whereas in the UK the most stakes winners come from the second quartile (red graph).

It means then the stakes-winning horses match exactly the same pattern as they sold for each region.

If looking a bit more broadly, this pattern is also repeated for the top 10 per cent of earners (bottom table).

When examining height quartiles, the top earnings in both regions were found to be in the third quartile. It really seems there is a sweet spot for racing performance in both regions and that is slightly different.

In the US this the fourth quartile body weight, third quartile height, In the UK it is second quartile body weight and third quartile height.