RESPONSE OF BROILER CHICKS TO ESSENTIAL AND NON-ESSENTIAL AMINO ACID SUPPLEMENTATION OF LOW CRUDE PROTEIN DIETS

Authors: CORZO, A - MISSISSIPPI STATE UNIV; FRITTS, C - MISSISSIPPI STATE UNV; KIDD, M - MISSISSIPPI STATE UNV; Kerr, Brian

Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2004
Publication Date: 1/10/2005
Citation: Corzo, A., Fritts, C.A., Kidd, M.T., Kerr, B.J. 2005. Response of broiler chicks to essential and non-essential amino acid supplementation of low crude protein diets. Animal Feed Science And Technology. 118:319-327.

Interpretive Summary: The efficiency of utilization of amino acids is best when all amino acids are at or slightly below, but not above, their need for protein accretion and maintenance. Formulating diets that meet, but do not exceed, amino acid needs also results in less nitrogen excretion. Formulating broiler diets on a digestible amino acid basis and utilizing the economically feasible commercial amino acid supplements (i.e., methionine, lysine, and threonine sources) results in diets marginally reduced in crude protein that support equal broiler growth compared to broilers fed diets containing higher crude protein with excess amino acids. Published reports involving the inclusion of amino acids other that methionine, lysine, and threonine sources whereby crude is reduced to the extent that numerous amino acid supplements are needed, vary in terms of the impact on broiler productivity. Differences in crude protein level, amino acid fortification, dietary ingredients, amino acid requirements imposed, bird age, and bird strain may have contributed to the discrepancies in the former reports. Moreover, it may be that non-essential amino acid needs also contributed to discrepancies in the former reports. The degree of limitation of most non-essential amino acids as dietary crude protein is reduced is unknown in broilers. Therefore, an experiment was conducted to evaluate the responses of the addition of various non-essential amino acids to a low crude protein diet in male broiler chicks. Experimentation indicted that supplementation of the low crude protein diets with glycine, leucine, and aspartic acid resulted in similar body weight gain of chicks fed a higher crude protein, control diet. Supplementation with glycine and leucine to the low crude protein diet resulted in similar feed conversion. Nitrogen retention was improved by feeding low crude protein, amino acid supplemented diets, and lowest with the higher crude protein, control diet. Results described in this report provide nutritionists at universities, feed manufactures, and broiler production facilities data on the potential need for certain non-essential amino acids in low crude protein diet formulations.

Technical Abstract: A study was conducted to evaluate individual and combined responses of non-essential crystalline amino acid supplementation to a low crude protein starter diet. Five hundred and forty Ross 508 day-old male chicks were placed in ninety petersime battery cages (6 chicks/cage). Birds were fed a pre-starter diet from placement until Day 5 formulated to meet or exceed NRC (1994) recommendations. They were subsequently fed dietary treatments from 5 to 21 days of age. Treatments consisted of a control diet (22% CP), a low crude protein (18%) diet supplemented with L-Lys, DL-Met, L-Thr, and L-Ile, six treatments composed of individual additions of Gly, L-Ala, L-Asp, L-Glu, L-Pro and L-Leu to the low crude protein diet, and the low crude protein diet with the combined supplementation of the aforementioned amino acids. At Day 13 the control and low crude protein diet supplemented with all the non-essential amino acids resulted in chicks with higher BW gain and feed conversion than all other treatments. At Day 21, supplementation with Gly, Leu and Asp to the low crude protein diet resulted in similar BW gain of chicks fed the control diet. Supplementation with Gly and Leu to the low crude protein diet resulted in similar feed conversion to that of chicks fed the control diet. Feed intake was unaffected by dietary treatments. Chicks fed the low crude protein diet or the low crude protein diets supplemented with individual amino acids, except Leu, had lower blood plasma uric acid concentration than chicks fed the control. Nitrogen retention was lowest with the control diet. Results indicate that when feeding chicks a diet reduced by four percentage points in crude protein, that there may be a need for certain non-essential amino acids.