HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS Top of Form QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:  Bottom of Form Institution: Alta Gov't Library - Neil Crawford Centre Site Sign In as Member This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Cited by other online articles Google Scholar Articles by Castillo, A. R. Articles by France, J. Articles citing this Article PubMed PubMed Citation Articles by Castillo, A. R. Articles by France, J. Journal of Animal Science, Vol 79, Issue 1 247-253, Copyright © 2001 by American Society of Animal Science JOURNAL ARTICLE The effect of protein supplementation on nitrogen utilization in lactating dairy cows fed grass silage diets A. R. Castillo, E. Kebreab, D. E. Beever, J. H. Barbi, J. D. Sutton, H. C. Kirby and J. France Department of Agriculture, University of Reading, UK. The study set out to examine the effects of supplementing grass silage with various levels of protein concentration and degradability on dietary nitrogen (N) excretion in lactating dairy cows consuming at least 60% forage. Six Holstein/Friesian cows in early to midlactation were offered six diets comprising two levels of crude protein (210 and 290 g/kg DM) and three levels of protein degradability in the concentrate achieved using different amounts of untreated or formaldehyde-treated soybean meal. Despite a difference of almost 100 g/d in N intake, apparent fecal and milk N outputs were not significantly affected. Protein degradability also had no effect on N outputs in feces and milk. However, there was a major effect of both level and degradability of CP on urinary N output. Moreover, an interaction between level and degradability of CP was detected, such that the rate at which urinary N increases with increasing CP degradability was higher on the high-CP than on the low-CP diet. A low level of protein (150 g/kg DM in the diet) and medium to low rumen-degradable protein supplements provided a significant reduction in N excretion without compromising lactational performance (mean 24.8 kg/d), in terms of both milk yield and composition. This study also demonstrated that a high efficiency of N utilization could be achieved on low-CP diets (supplying less than 400 g N/d), with feces being the main route of N excretion, whereas an exponential excretion of urinary N was observed as N intake exceeded 400 g N/d. This article has been cited by other articles: (Search Google Scholar for Other Citing Articles) S. M. Reynal and G. A. 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[Full Text] HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS Copyright © 2001 by the American Society of Animal Science.