EFFECTS OF MILKING FREQUENCY AND SELECTION FOR MILK-YIELD ON PRODUCTIVE EFFICIENCY OF HOLSTEIN COWS

One hundred primiparous Holstein cows, either daughters of cows randomly bred to noncommercial sires (estimated mean PD milk = –467 kg, control cows) or to daughters of commercially available sires (mean PD milk = +398 kg, selection cows), were randomly assigned to be milked twice or thrice daily beginning at parturition. Dry matter intake, BW, milk yield, and fat content and measures of reproductive efficiency were recorded for two lactations. Selection group cows yielded approximately 25 and 30% more milk during first and second lactation, respectively, than control cows. Dry matter intake, but not BW or milk fat percentage, was increased by selection for milk yield. Milk yield per unit of DM intake was greater for selection cows than for controls at 30, 90, and 200 d postpartum. Milking three limes daily increased milk yield overall by 14 and 6% during first and second lactation, respectively. Interactions were present whereby control cows experienced greater milk yield response to three times daily milking than did selection cows. Cows milked three times daily had decreased milk fat percentage and tended to weigh less, suggesting more body tissue was catabolized for milk production, since DM intake was not altered from that of cows milked twice daily. Neither selection for milk yield nor increased milking frequency affected conception rates or days open. © 1990, American Dairy Science Association. All rights reserved.