Effect of Production and Ration Composition on Production Performance of Cows Fed Mixed Rations of Corn Silage and Concentrates

Abstract

Corn silage and concentrates were mixed at time of feeding to form low-medium-and high-energy complete feeds which were fed for four 8-week periods as the only source of energy and protein to groups of cows producing low, medium, and high daily amounts of milk. Rate of decrease in daily milk production for cows receiving medium-and high-energy feeds was associated only slightly with initial production. However, a greater reduction (P<0.01) in daily production of 4% fat-corrected milk associated with higher initial fat-corrected milk was found in cows receiving high energy feed. Initial milk was associated with decrease in daily production for the cows receiving low energy feed (P<0.01). The direction of constants for milk, fat-corrected milk and body weight changes were consistent with overfeeding low relative to high producers within a group. A combined analysis across all feeds indicated that the reduction in daily milk production of cows receiving medium-energy feed was less than for those receiving high energy feed. Complete feeds containing 45 to 50% concentrates and 50 to 55% corn silage adequately supported milk production when the mixture was fed ad libitum. However, interpretation of responses for cows producing above 30kg daily was limited by small numbers of observations.Number of observations, mean initial daily milk production (kg), least-squares means for decrease in daily milk (kg), and increase in body weight (kg/week) were 48,14.5,1.93, 4.11, 71, 20.6, 2.10, 3.61, 60, 26.9, 3.34, 2.72 for the cows receiving the low, medium- and high-energy feeds.