Performance of First Lactation Dairy Cows Fed Complete Rations of Several Ratios of Forage to Concentrate

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Abstract
Holstein cows (74) in 1st lactation averaging 27.6 mo. of age at parturition were fed blended diets ad lib with ratios of forage to concentrate (dry basis) of 80:20, 65:35, 50:50 or 35:65 from 7-16 wk of lactation. Of the forage in each diet, 2/3 was early bloom alfalfa-brome hay and 1/3 was well matured corn silage. Daily yields of actual milk, 4% fat-corrected milk and solids-corrected milk, were each adjusted for preexperimental yield by covariance. Actual milk yield increased curvilinearly and solids-corrected milk yield increased linearly; fat-corrected milk yield was unaffected as ratios of forage to concentrate decreased. Milk fat percent decreased and milk protein percent increased curvilinearly whereas lactose increased linearly with decreasing ratios of forage to concentrate. Feed intake increased as did live weight and heart girth but not wither height as ratios of forage:concentrate decreased.