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Journal of Dairy Science Vol. 62 No. 6 954-964
© 1979 by American Dairy Science Association ®
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Influence of Protein Percent and Source on Cows in Early Lactation1

J. Foldager2 and J. T. Huber

Department of Dairy Science, Michigan State University, East Lansing 48824

ABSTRACT

Four rations were compared in 68 lactating cows (17 per group) from 14 to 140 days postpartum. Treatments were negative control (12.5% crude protein of plant origin), positive control (16% crude protein of plant origin), urea (16% crude protein-75% from plant origin, 25% from urea in both urea-treated silage and in concentrate), ammonia-urea (16% crude protein-similar to urea except that silage was treated with ammonia). Mean daily milk yields, adjusted by covariance, from 3 to 20 wk did not differ and were 28.0, 29.0, 27.9, and 27.5 kg for the respective treatments. For wk 3 to 6 postpartum, high producing cows (over 25 kg during wk 2) from the positive control outyielded those on urea. Intakes of dry matter and calculated net energy did not differ between treatments but were generally higher for the negative control. Production of milk or composition of its major components did not differ. Rumen ammonia and urea of plasma reflected quantities of protein and nonprotein nitrogen fed. Milk yields of cows in early lactation were not significantly increased by added soybean meal or by nonprotein nitrogen to raise the crude protein of corn silage-type rations from 12.5 to 16%.

FOOTNOTES

1 Published with the approval of the Director of the Agricultural Experiment Station as Journal Article No. 8625.

2 National Institute of Animal Science, Department of Cattle and Sheep Experiments, 25 Rolighedsvej, DK-1958, Copenhagen V, Denmark.






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Copyright © 1979 by the American Dairy Science Association ®.