Varying Energy in a Complete Feed for High-Producing Cows

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Abstract
Twelve lactating Holstein cows which had been in production for at least 40 days were used in a series of four (3 X 3) Latin squares to determine the com- parative effects of three complete feeds of varying energy (A-60, B-65, and C- 70 Mcal estimated net energy per 45.45 kg dry matter). Grain sorghum silage was the only source of roughage. The daily means for rations A, B, and C were: dry matter intake---17.8, 19.9, and 21.6 kg; estimated net energy in- take-22.8, 28.5, and 33.1 Meal; 4% fat- corrected milk yield-19.1, 20.9, and 22.6 kg; and solids-corrected milk yield-18.6, 20.8, and 22.7 kg. Milk constituents also increased with increased energy in the ration; the means for rations A, B, and C were: milk fat 3.5, 3.4, and 3.6%; total solids 11.8, 11.9, and 12.2%; solids-not- fat 8.3, 8.5, and 8.8%; and protein 3.0, 3.1, and 3.2%. No differences were signif- icant in the molar percentages of rumen volatile fatty acids. As the energy of the ration increased, efficiency of energy utilization decreased.
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