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

Abstract

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.

The Effect of Varied Dietary Crude Protein Levels with Balanced Amino Acids on Performance and Egg Quality Characteristics of Layers at First Laying Phase

“…In addition, [10] found that chronic heat exposure significantly decreased protein digestion and reported that the feed digestibility of different components of the diets (protein, fats, starch) decreased with exposure of chickens to high temperature. The results of the present study agree with those of other studies, which indicated that reduction of dietary CP to 16% did not significantly affect the body mass gain of growing chicken [11,12]. In the same vein, [13] stated that increasing the crude protein content of the diet will increase egg production, egg weight and bird's weight but if the crude protein is included beyond the required level there will be no significant differences in egg production, egg weight and bird's weight.…”

Effect of Sauropus Androgynus Leaves Extract (Sale) on Fat Deposition in Broiler Fed Low Protein Diets

“…Hernandez et al (2012) found that the reduction of protein levels by 1.5% or 3.0% decrease nitrogen excretion into the environment of 9.5 and 17% in male broilers, and 11.8 and 14.6% in females. On the other hand, feeding low protein diets increased fat deposition in broiler chickens (Farahdiba et al, 2011;Jlali et al, 2012;Labussiere et al, 2008: Pesti, 2009Wood et al, 2004) .…”

Ideal Protein Concept in Broiler Starter Phase (0-28 Days) Using Low-Protein Diets Supplemented with the Most Limiting Essential Amino Acids

“…However, some other studies on low protein diets for broilers [13] showed depressed feed intake and was reported as the negative effect of low crude protein (LCP). The variations in the WG and FCR values for the broiler starter phase of production can best be explained by the several corroborative studies [3,4,14,15,16,17]. It has been reported that chickens fed low-protein feeds, despite having enough of each essential amino acid (to support excellent growth), failed to thrive and were excessively fat.…”

“…It has been reported that chickens fed low-protein feeds, despite having enough of each essential amino acid (to support excellent growth), failed to thrive and were excessively fat. It was realized that chickens require the essential amino acids plus some other amount of nonessential amino acids to synthesize protein at acceptable rates [17]. Therefore, it was clear that chickens require not only the essential amino acids but also some other quantity of amino acids, which have been referred to as the "nonessential" amino acids.…”