Using crystalline amino acids to supplement broiler chicken requirements in reduced protein diets

Abstract

Reducing dietary CP can reduce N pollution. Much research has been reported in corn-based diets; however, the amino acid ( AA ) profiles of wheat-based diets differ. Poor performance as a result of reduced protein ( RP ) has been overcome in corn-based diets with essential AA and glycine ( Gly ) supplementation. The current study examined RP levels and Gly in wheat-based diets. An industry standard protein ( SP ) diet plus 3 RP diets with and without Gly supplementation, to match the SP treatment at 0.713 and 0.648% digestible Gly for the grower and finisher periods respectively, were fed to male broilers from day 10 of age. Grower CP included 22.5, 20.6, 18.3, and 17.7% (days 10–21) and finisher CP included 19.7, 17.8, 16.2, and 15.5% (days 21–35). Performance, meat yield, N efficiency, water intake, and apparent ileal digestibility of N and AA were measured. No difference in body weight gain ( BWG ), feed intake, or feed conversion ratio ( FCR ) were observed at 20% CP compared to the SP treatment. However, further reducing protein reduced BWG ( P < 0.001), feed intake ( P < 0.001), and increased FCR ( P < 0.001). Supplementation of 0.713% Gly in the grower period increased BWG ( P < 0.001) and reduced FCR ( P < 0.001). Relative meat yield was not affected by dietary protein, however reducing CP increased relative fat pad weight ( P < 0.001). Nitrogen efficiency increased with decreased CP in both grower (R 2 = 0.69) and finisher (R 2 = 0.80) treatments. Water intake decreased (R 2 = 0.83) with decreasing CP intake. Apparent ileal digestibility of AA and N were higher in RP diets ( P < 0.05). The benefits of reduced water intake and increased N efficiency and the disadvantages of poor performance and increased body fat in RP corn-based diets have been identified in RP wheat-based diets. Furthermore, at 18.5% CP the supplementation of crystalline AA and Gly can maintain BWG and FCR observed in SP diets.

The Response of Broiler Chickens to Dietary Soybean Meal Reduction with Glycine and Cysteine Inclusion at Marginal Sulfur Amino Acids (SAA) Deficiency

“…Each percent reduction of protein in the diet reduced 10% of the N excretion [36]. Our study confirmed that a reduced protein diet reduced nitrogen excretion, which is in agreement with the reduction of nitrogen emissions in feces [19,31,32,[36][37][38].…”

Effects of Dietary Crude Protein Levels on Fecal Crude Protein, Amino Acids Flow Amount, Fecal and Ileal Microbial Amino Acids Composition and Amino Acid Digestibility in Growing Pigs

“…Other studies have shown that adding branched chain AA to low-protein diets can improve the growth performance in pigs to a level similar to that of adequate protein diets [22]. In addition, crystalline AA can provide growth requirements for broilers in low-protein diets [23]. In conclusion, added EAA to low-protein diet can make up for the problem of protein deficiency, and even improve animal production performance and lipid metabolism.…”

Impact of Reduced Dietary Crude Protein in the Starter Phase on Immune Development and Response of Broilers Throughout the Growth Period

“…As animals require specific amino acids, formulations requiring specific amino acids often lead to crude protein (CP) levels that are overly costly and result in excess nitrogen being excreted as an environmental pollutant ( 10 ). The industry has therefore taken strides to formulate diets on a digestible amino acid basis, rather than formulating on crude protein levels, which are much less precise ( 11 ). The resulting reduction in crude protein is made possible through the supplementation of the diet with crystalline amino acid sources to supply sufficient limiting essential amino acids ( 11 – 13 ).…”

“…The industry has therefore taken strides to formulate diets on a digestible amino acid basis, rather than formulating on crude protein levels, which are much less precise ( 11 ). The resulting reduction in crude protein is made possible through the supplementation of the diet with crystalline amino acid sources to supply sufficient limiting essential amino acids ( 11 – 13 ). While extensive research has been conducted to determine the standard ileal digestible amino acid requirements for all feeding phases of broiler chickens in healthy conditions ( 14 ), the requirements for optimal immune development, or during a challenge, remain largely unknown ( 15 ).…”