Table 5
Additive genetic (σ²_a), animal permanent environmental (σ²_pe), residual (σ²_e) variances and heritability (h²) of the test-day records of milk yield (Kg) for some selected days in milk and different milking frequency

Variances	Days in milk (DIM)
	5–35	36–65	66–95	96–125	126–155	156–185	186–215	216–245	246–275	276–305
Lact 1 (3X)
σ2a	5.0	5.7	4.9	5.2	6.1	8.1	9.1	8.0	8.5	21.7
σ2pe	9.2	11.0	11.7	11.3	11.9	13.4	15.2	17.8	20.0	18.1
σ2e	11.4	10.0	9.1	8.5	9.4	8.5	8.9	9.2	7.5	7.7
h2	0.20	0.21	0.19	0.21	0.22	0.27	0.27	0.23	0.24	0.46
Lact 2 (3X)
σ2a	4.0	4.1	6.3	6.8	7.3	9.9	14.0	16.4	14.7	12.3
σ2pe	25.5	21.7	22.3	24.2	25.6	25.7	25.1	25.4	29.3	40.9
σ2e	20.9	19.0	15.7	14.3	13.4	12.7	12.5	11.5	11.2	10.1
h2	0.08	0.09	0.14	0.15	0.16	0.20	0.27	0.31	0.27	0.19
Lact 1 (4X)
σ2a	10.1	8.9	12.0	11.6	11.5	11.2	11.0	9.5	9.1	13.5
σ2pe	20.3	14.3	11.6	10.7	10.6	10.9	11.4	12.7	15.6	21.6
σ2e	8.9	9.5	8.6	8.3	8.5	7.3	7.8	6.0	6.5	6.0
h2	0.26	0.27	0.37	0.38	0.38	0.38	0.36	0.34	0.29	0.33
Lact 2 (4X)
σ2a	16.6	12.0	10.4	10.0	8.7	10.2	14.4	16.6	19.2	15.5
σ2pe	18.5	25.0	27.2	26.9	26.1	25.8	25.8	25.9	27.6	37.2
σ2e	21.6	16.4	15.2	11.6	12.3	11.4	8.9	8.0	7.9	6.7
h2	0.29	0.23	0.20	0.21	0.18	0.22	0.29	0.33	0.35	0.26