Heritabilities for Body Size and Growth Rate and Phenotypic Correlations among Measurements in Young Horses

The data consisted of the eight body measurements: body weight, height at withers, height at croup, heart girth, body length, chest width, chest depth and circumference of front cannon bone recorded at birth and then approximately at age of 6, 12, 18, 24, 30, 36 and 48 months for totally 488 Finnhorse foals. The variation in body measurements was largest in body weight (7.3–14.9%) and smallest in height measurements (2.4–4.6%), and decreased with increasing age. In general, heritability (h 2) estimates for body measurements estimated on the basis of paternal half-sib analysis (PHS) and offspring-on-dam regression (ODR) were fairly high, and increased with increasing age. The highest h 2-estimates (by PHS) were observed for body weight (0.22±0.16 to 0.88±0.27) and the lowest for cannon bone circumference (0.25±0.17 to 0.56±0.20). Heritability estimates (by PHS) for daily weight gain ranged between 0.08±0.16 and 0.86±0.32, and for cumulative growth in height at withers between 0.00±0.14 and 0.67±0.27. In general, the body measurements were mutually quite highly correlated. In conclusion, selection of foals showing optimum development and body size is possible. Selection for body size at the age of one year may lead to the selection for fast growth.