The overall least square means of first lactation milk yield (kg), average daily milk yield (kg), first lactation length (d), fat (%), protein (%), lactose (%) and solids- not-fat (%) were found to be 2572.27±41.12, 8.42±0.13, 296.68± 3.46, 4.52±0.02, 3.47±0.01, 4.08±0.02 and 8.40±0.01, respectively. Location and age at sexual maturity had a significant effect on first lactation milk yield and average daily milk yield. Season of birth had significant effect on protein was non-significant on other components of milk. Year of birth had significant effect on protein and solids-not-fat but not on fat and lactose. Location had a significant effect on fat and lactose only. Age at sexual maturity had a significant effect on lactose and SNF whereas, fat and SNF were non-significant. Season of calving had a significant effect on lactose and SNF and had non-significant effect on first lactation milk yield, average daily milk yield, first lactation length, fat, protein, services per conception for second pregnancy and first service period. Year of calving had significant effect on first lactation milk yield, average daily milk yield, first lactation length, fat, lactose and SNF but non significant for protein, services per conception for second pregnancy and first service period were non-significant. Heritability estimates of first lactation milk yield, average daily milk yield, first lactation length, fat, lactose, protein and SNF were 0.44±0.10, 0.20±0.10, 0.15±0.02, 0.09±0.06, 0.04±0.06, 0.13±0.11 and 0.06±0.11, respectively.

Highlights

• Progeny testing is the method commonly employed in sire selection.
• The estimated overall means indicates production potential of crossbred Jersey cows (Jersey × Sahiwal) under progeny testing program.