Table 1 Variables recorded by examination, interview and records from the Norwegian Trotting Association (NTA) with units, range (continuously distributed variables) and number of observations in each category (categorized variables).

Height (tape measure) corrected to 24 months age

Centimetres

Chest circumference

Centimetres

Body condition

Normal/Abnormal

Conformational abnormalities

Normal/Abnormal

Age at examination

Months

Age at weaning

Months

Age at introduction to concentrated feeds

Months

Amount of concentrated feeds/day at time of examination

Litres

Time spent at pasture 1^st summer

Weeks

Topography of pasture 1^st summer

Flat/Intermediate/Hilly

Group size at pasture 1^st summer

Horses

Number of foals in pasture group 1^st summer

Foals

Daily time spent in paddocks 1^st winter

Hours

Time spent at pasture 2^nd summer

Weeks

Topography of pasture 2^nd summer

Flat/Intermediate/Hilly

Group size at pasture 2^nd summer

Horses

Number of yearlings in pasture group 2^nd summer

Yearlings

History of diseases

Yes/No

Accustomed to sulky before pasture 2^nd summer

Yes/No

Horse sold prior to examination

Yes/No

Started training before age 18 months

Yes/No

Trained by professional trainer at time of examination

Yes/No

Variables obtained from the NTA:

Gender

Colt/Filly

Sires BLUP-index

-

Dams BLUP-index

-

BLUP estimate*

-

Passed Recruitment race

Yes/No

Raced before end of three year season (2008)

Yes/No

Raced until the 28^th of October 2009

Yes/No