Table 1.

Heritability estimates for lactation traits

Trait	$h_{\mathrm{HF}}^2$ (SE)	${\delta }_{\mathrm{HF}}^2$ (SE)	$h_{\mathrm{J}}^2$ (SE)	${\delta }_{\mathrm{J}}^2$ (SE)
Milk volume	0.296 (0.010)	0.044 (0.007)	0.312 (0.012)	0.064 (0.009)
Milk fat yield	0.261 (0.010)	0.059 (0.008)	0.232 (0.012)	0.074 (0.010)
Milk protein yield	0.235 (0.009)	0.053 (0.008)	0.236 (0.012)	0.073 (0.010)
Milk fat percentage	0.700 (0.007)	0.006 (0.004)	0.616 (0.010)	0.015 (0.006)
Milk protein percentage	0.642 (0.008)	0 (0.005)	0.636 (0.010)	0.005 (0.005)

$h^2$: additive heritability: ${\delta }^2$: dominance heritability; HF: Holstein–Friesian, J: Jersey; SE: standard error