Two approaches to account for genotype-by-environment interactions for production traits and age at first calving in South African Holstein cattle

Table 6 Herd characteristics, estimates of heritability (in bold) and genetic correlations (below the diagonal of bold figures) for milk yield when herds are grouped according to average rainfall (Model RF4)

Level of average rainfall (mm)	Proportion of herds with pasture^a	Milk production
Level of average rainfall (mm)	Proportion of herds with pasture^a	Mean	Residual standard deviation	Heritability and genetic correlations
> 755	80.5	5962	783	0.268
> 659 and < 755	48.8	6070	797	0.909; 0.306
> 547 and < 659	11.7	7746	1016	0.779; 0.991; 0.257
< 547	1.8	7989	1062	0.829; 0.858; 0.862; 0.250

^aInformation on feeding system was available only on a limited fraction of the herds

ISSN: 1297-9686