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Department of Dairy Science
and Department of Agricultural Engineering, University of Wisconsin, Madison 53706
ABSTRACT
Twenty dairy cows were allotted to two treatment groups in a continuous feeding experiment over two lactation cycles. Cows in Group 1 were fed ad libitum to assure 5% orts, a constant 60:40 forage-to-grain ratio (dry basis) whereas Group 2 cows were fed 50:50, 63:35, and 85:15 ratios during early (Period 1, 21 wk) and late (Period 2, 23 wk) lactation, and the dry period (Period 3, 8 wk). There was no significant difference between Groups in the 2-yr average 308-day actual or 4% fat-corrected milk. The 4% fat-corrected milk production during lactations 1 and 2 for Group 1 was 6591, 6398 and for Group 2 was 6006, 6678 kg. Fat test was higher during early lactation in Group 1; otherwise milk composition data were similar. The 2-yr average daily and yearly total dry matter intakes were not different between treatments. Digestible energy concentration of diets for Groups 1 and 2 during Periods 1, 2, and 3 were: 2.88, 2.93; 2.90, 3.08; and 2.99, 2.93 Mcal/kg dry matter. Cows in Group 2 had a more positive energy balance during early lactation, produced more actual milk, consumed more dry matter, lost less body weight, had higher blood glucose and lower ketone values, showed an earlier postcalving estrus, and recovered lost postpartum weight faster than cows in Group 1.
1 Research supported by die College of Agricultural and Life Sciences, University of Wisconsin, Madison, and by Hatch Project 6003.
2 Land O'Lakes, Inc., Fort Dodge, IA 50501.
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