HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pesti, G. M. Search for Related Content PubMed Articles by Pesti, G. M.

Impact of dietary amino acid and crude protein levels in broiler feeds on biological performance

Department of Poultry Science, The University of Georgia, Athens 30602-2772

¹ Corresponding author: gpesti{at}uga.edu, gpesti{at}bellsouth.net

The concept of a requirement for dietary protein has been controversial since it was discovered that proteins are composed of amino acids and that some amino acids are dietary essentials for maximum growth and performance. In addition to the 10 essential amino acids and 3 that can be accreted only from limited substrates, poultry need a quantity of amino acids to synthesize the other 8 that are needed to synthesize body proteins. Adding purified amino acids or amino acid precursors has been known for more than 50 yr to allow for reduced levels of intact proteins to provide adequate levels of essential and nonessential amino acids (CP). It has been recognized that individual essential amino acid requirements are functions of the total CP level. Increasing the total CP level while maintaining ideal ratios of essential amino acids increases growth, feed utilization efficiency, and carcass yields (i.e., decreases carcass fat). A published data set is used here to demonstrate 1) that potential problems arise from analyzing combined data sets inappropriately; 2) that in the overwhelming majority of studies, there is a positive response in growth (P < 0.0002) and feed utilization efficiency (P < 0.0002) to increasing dietary protein levels; 3) that the relationships are much stronger in faster growing broiler strain birds; and 4) that there is no clear break point or "requirement" for CP in the range of dietary protein levels typically studied. Regardless of whether it is called "CP level" or "essential + nonessential amino acid level," there is no clear requirement, only a smooth response curve that approaches maxima at lower levels for growth, and then feed utilization efficiency, and then lean meat yield, and finally the minimum for carcass fat. As a result, decisions on feeding levels for essential and nonessential amino acids should depend on the input-output relationships and costs.

Key Words: broiler • amino acid • crude protein • requirement • model