Influence of Sire Selection and Milking Frequency on Milking Characteristics in Holstein Cows

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Abstract
Sixty-five Holstein cows, either second to fourth generation daughters of cows randomly bred to noncommercial sires originating in the Virginia Tech dairy herd [estimated mean PD milk (1982) = -455 kg, control animals], or daughters of cows bred to commercially available AI sires [weighted mean PD) milk (1982) = +402 kg, selection animals] were used. Cows were randomly assigned to be milked twice or three times daily for two lactations starting at first parturition. Primary and residual milk yield per milking, total milk yield (total daily primary plus residual milk), machine milking time, and average milk flow rate were recorded at 50, 100, and 150 d postpartum. Selection cows produced more primary milk and total milk per day and required more machine time per milking than control cows. Quantities and percentages of residual milk were similar between selection and control cows but were greater in second lactation than in first lactation. Three times daily milking reduced primary milk yield, and machine milking time per milking, and average rate of milk flow at milking compared with twice daily milking. Daily primary milk yield was increased in first lactation cows milked three times daily and total milk was increased overall as a result of milking three times per day. Cows milked three times daily yielded more residual milk and required approximately 28% more machine milking time per day than did cows milked twice daily.