Protein levels and essential-to-total nitrogen ratio in diets for broiler chickens

• Ano de defesa: 2024
• Autor(a) principal: Ferreira, Rafael de Sousa
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa; Zootecnia
• Palavras-chave em Português: Frango de corte - Nutrição; Aminoácidos na nutrição animal; Nitrogênio na nutrição animal; Proteínas na nutrição animal; CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL
• Link de acesso: https://locus.ufv.br/handle/123456789/32709; https://doi.org/10.47328/ufvbbt.2024.348

Two experiments were carried out to evaluate the effects of essential: total nitrogenratios (eN-to-tN) in reduced crude protein (CP) diets supplemented with non-essential amino acid (NEAA) (experiment I), and NEAA mixture and mixture and non-protein nitrogen (experiment II) on performance, nitrogen retention, metabolizable energy values, and amino acid digestibility from broiler chickens from 12 to 23 days of age. In the first experiment experiment, 576 broilers were used and allocated to eight treatments: T1 (positive control) - 220 g/kg CP and 0.50 eN-to-tN ratio; T2 - 200 g/kg CP (0.54 eN-to- tN); T3- 200 g/kg CP + 9.84 g/kg NEAA mixture (0.52 eN-to-tN); T4 - 200 g/kg CP + 18.51 g/kg NEAA mixture (0.50 eN-to-tN); T5 - 190 g/kg CP (0.50 eN-to-tN); T6 - 190 g/kg CP + 14.92 g/kg NEAA mixture (0.54 eN-to-tN); T7 - 190 g/kg CP + 22.93 g/kg NEAA mixture (0.52 eN-to-tN); T8 - 190 g/kg CP + 31.58 g/kg NEAA mixture (0.50 eN- to-tN). Decreasing eN-to-tN ratio from 0.58 to 0.50 improves the final body weight, body weight gain, and feed conversion ratio of broilers from 12 to 23 d post-hatching. A high retained nitrogen was observed on broilers fed diet with eN-to-tN ratio of 0.58 or 0.54 when compared to broilers fed eN-to-tN ratio of 0.50. Reducing CP from 220 to 200 or 190 g/kg with supplementation of NEAA, reaching eN-to-tN ratio of 0.58 to 0.50 resulted in higher metabolizable energy utilization and improved amino acid digestibility. In the second experiment, 648 broilers were used and allocated to eight treatments. The first treatment was a positive control with 220 g/kg CP and eN-to-tN ratio of 0.50. The second treatment was a negative control with 190 g/kg CP and an eN-to-tN ratio of 0.58. From negative control, other seven dietary treatments were formulated, supplementing the diets with 190 g/kg CP with different levels of NEAA mixture (60% Ala, 20% Gly, 20% Glu) and non-protein nitrogen (urea, ammonium acetate, monoammonium phosphate). The results show that reducing CP from 220 to 190 g/kg without supplementation of NEAA mixture or non-protein nitrogen compromised (P<0.05) the growth performance of broilers. However, a decrease in nitrogen intake and nitrogen excretion was observed in the negative control treatment. Metabolizable energy values decreased when negative control treatment was supplemented with NEAA mixture combined with ammonium acetate or monoammonium phosphate. Apparent and standardized ileal digestibility of some amino acids increased when there was a reduction of CP when compared to those fed with positive control treatment. The supplementation of NEAA and/or non-protein nitrogen seems to be efficient in a diet with reduced CP, allowing a reduction from 220 to 190 g/kg of CP and achieve an eN-to-tN of 0.50. Keywords: amino acids; broilers; ideal protein; nitrogen