Classification of breeds into phenotypically contrasting cohorts
From the FAO data (DAD-IS 2014), the overall lower quartile (Q1), median, and upper quartile (Q3) for the combined values for wither height of 47 European breeds were 134 cm, 140 cm, and 143 cm, respectively (Figure 1A). In comparison, the median wither height for the European large (11 breeds) and European small (12 breeds) stature cohorts were 146.8 cm and 129.5 cm, respectively (Table S1, Figure 1A). The minimum median (145 cm of Charolais and Montbeliarde breeds) of the large cohort and the maximum median (133.5 cm of Finnish Ayrshire and Belted Galloway breeds) of the small cohort values were separated by 11.5 cm.
Figure 1  Distribution of the wither height (cm) of the 47 European (A) and eight African (B) Bos taurus breeds. Each colored dot represents the median of a breed’s stature using FAO data from the multiple countries and the vertical error bars range between the upper and lower quartiles. Several breeds are represented from a single country; therefore, they do not have error bars. The horizontal dashed red, green, and blue lines, respectively, represent the overall upper quartile, median, and lower quartile of all breeds’ data. The red, green, and blue dots represent cattle breeds categorized in the large, medium, and small stature cohorts, respectively (see Figure S1). Boxplots show distribution of breed median data for stature within each cohort. Similarly using the FAO data for the eight African breeds, overall Q1, median, and Q3 for wither heights calculated were 100 cm, 106 cm, and 115 cm, respectively (Figure 1B). The median wither heights for the African large (two breeds) and African small (three breeds) stature cohorts were 138.5 cm and 97.5 cm, respectively (Table S2). The separation of closest medians at the tails of the two African cohorts was 31.7 cm.
Overall, the distribution of breed-wise data (Figure 1) shows that implementing the stringent grouping strategy resulted in a clear separation (contrast) of wither height (stature) between the large and the small cohorts of the European and African categories.