Table 4.

Variance component and genetic parameter estimates for lactation pattern and milk production traits and lactation curve parameters

Trait1	Variance components2				Genetic parameters3
	${\sigma }_a^2$	${\sigma }_{\mathit{pe}}^2$	${\sigma }_e^2$	${\sigma }_p^2$	h2	r
LY (kg)	84,166	71,259	139,090	294,514	0.29±0.04	0.53±0.01
IY (kg)	2.2	0.5	4.1	6.8	0.33±0.04	0.39±0.02
PY (kg)	2.1	1.2	3.4	6.8	0.32±0.04	0.49±0.02
YD (kg)	0.9	0.6	1.4	2.9	0.30±0.04	0.51±0.02
DP (d)	52	38	557	647	0.08±0.02	0.14±0.01
LL (d)	547	1,395	7,358	9,300	0.06±0.03	0.21±0.02
ln(a) (kg)	0.04	0.01	0.12	0.16	0.21±0.03	0.27±0.02
c (kg/d)	0.0000004	0.0000034	0.0000120	0.0000157	0.03±0.03	0.24±0.02

¹LY = Lactation milk yield; IY = Initial milk yield; PY = Peak milk yield; YD = Average yield per d; DP = Days to peak; LL = Lactation length; ln(a) and c = parameters of the MIG function.

² ${\sigma }_a^2$ = Additive genetic variance, ${\sigma }_e^2$ = Residual variance, ${\sigma }_{\mathit{pe}}^2$ = Permanent environmental variance, ${\sigma }_p^2$ = Phenotypic variance.

³h² = Heritability, r = Repeatability.