Leucine and valine supplementation of low-protein diets for broiler chickens from 21 to 42 days of age

Ospina-Rojas, I. C.
Murakami, A. E.
Duarte, C. R. A.
Nascimento, G. R.
Garcia, E. R. M.
Sakamoto, M. I.
Nunes, R. V.

^*Department of Animal Science, Universidade Estadual de Maringá; Av. Colombo, 5790, Bloco J45, 87020–900, Maringá, PR, Brazil
^†Department of Animal Science, Universidade Estadual de Mato Grosso do Sul; Rodovia Aquidauana, km 12, 79200–000, Aquidauana, MS, Brazil
^‡Department of Animal Science, Universidade Camilo Castelo Branco; Av. Hilario da Silva Passos, 950, 13690–970, Descalvado, SP, Brazil
^§Department of Animal Science, Universidade Estadual do Oeste do Paraná, Marechal Cândido Rondon; Rua Pernambuco, 1777, 85960–000, PR, Brazil

Accepted July 31, 2016.

Received April 24, 2016.

Poultry Science (PS) 96(4):p 914-922, April 2017. | DOI: 10.3382/ps/pew319

ABSTRACT

The objective of this study was to determine the requirements and interactions between the standardized ileal digestible (SID) Leu and Val levels in low-protein diets, and their effects on performance, serum characteristics, carcass yield and diameter of muscle fibers of broiler chickens from d 21 to 42 posthatch. A total of 1,500 21-day-old Cobb 500 male broiler chickens were distributed in a completely randomized design in a 5 × 5 factorial arrangement for a total of 25 treatments with 3 replicates of 20 birds each. Treatments consisted of 5 SID Leu levels (1.0, 1.2, 1.4, 1.6, or 1.8%) and 5 SID Val levels (0.52, 0.67, 0.82, 0.97, or 1.12%). At 42 d of age, there was interaction (P < 0.05) between the SID levels of Leu and Val on feed intake and weight gain. There was a quadratic effect (P < 0.05) of Leu and Val levels on feed conversion, with minimal point estimated at the levels of 1.19 and 0.86%, respectively. Dietary Leu supplementation reduced linearly (P < 0.05) serum concentrations of triglycerides and β-hydroxybutyrate. Dietary Leu increased (P ≤ 0.05) the fiber diameters of the pectoralis major muscle and breast yield at the levels of 1.24 and 1.13%, respectively, while the thigh yield was improved with the level of 0.71% Val. Abdominal fat decreased linearly (P < 0.05) with increasing levels of dietary Leu and Val. The SID Leu and Val levels needed to optimize weight gain and feed conversion in low-CP diets for broiler chickens from d 21 to 42 posthatch were estimated at 1.15 and 0.86%, and 1.19 and 0.86%, respectively. The supplementation of Leu and Val can reduce the abdominal fat deposition in birds fed low-CP diets during the grower phase. Leu and Val interactions can influence the performance but not the serum characteristics, carcass yield and diameter of muscle fibers of broilers fed low-protein diets. Therefore, it is necessary to consider the dietary Leu content to estimate the ideal level of Val in low-CP diets for optimum broiler performance.