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Utilization of nutrients by the dairy cow and optimal N:energy ratio in the diet
Published online by Cambridge University Press: 01 June 2009
Summary
The dietary and individual animal factors influencing the utilization of digestible nitrogen and of metabolizable energy for milk production were studied and change in the optimal nitrogen:energy ratio during lactation was investigated using 35 different experimental diets and the individual results obtained from 119 Friesian cows whose daily milk production varied from 4 to 30kg.
The amount of N secreted in the milk and the daily milk production depended above all on the metabolizable energy intake and on the stage of lactation. They were related to the dietary N: energy ratio.
The percentages of digestible N and of metabolizable energy utilized for milk production were also related to the dietary digestible N: metabolizable energy ratio of the diet.
The optimal digestible N:metabolizable energy ratio ranged from about 2·2g/MJ during the first 3 months of lactation to about 1·7g/MJ in the sixth and seventh months and 1·3g/MJ from the tenth month. When expressed in g N intake per MJ energy intake, this optimal ratio ranged from 1·6 after calving to 1·1 at the end of lactation.
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- Copyright © Proprietors of Journal of Dairy Research 1973
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