The Revista Brasileira de Zootecnia (RBZ) is a publication dedicated to the broad field of Animal Science. We publish high-quality, original scientific research that spans across diverse areas within the discipline. The scope of RBZ encompasses a wide range of topics, including aquaculture, biometeorology and animal welfare, forage crops and grasslands, animal and forage plants breeding and genetics, animal reproduction, ruminant and non-ruminant nutrition, meat science and muscle biology, precision livestock, and animal production systems and agribusiness.
The Revista Brasileira de Zootecnia (RBZ) is a publication dedicated to the broad field of Animal Science. We publish high-quality, original scientific research that spans across diverse areas within the discipline. The scope of RBZ encompasses a wide range of topics, including aquaculture, biometeorology and animal welfare, forage crops and grasslands, animal and forage plants breeding and genetics, animal reproduction, ruminant and non-ruminant nutrition, meat science and muscle biology, precision livestock, and animal production systems and agribusiness.
The Revista Brasileira de Zootecnia (RBZ) is a publication dedicated to the broad field of Animal Science. We publish high-quality, original scientific research that spans across diverse areas within the discipline. The scope of RBZ encompasses a wide range of topics, including aquaculture, biometeorology and animal welfare, forage crops and grasslands, animal and forage plants breeding and genetics, animal reproduction, ruminant and non-ruminant nutrition, meat science and muscle biology, precision livestock, and animal production systems and agribusiness.
Two experiments were conducted with the objective of evaluating the lysine requirements for Ross broilers, males, from 22 to 42 and 43 to 49 days old, maintaining 71% met + cys:lys ratio. Nine hundred broilers averaging initial body weight of 780 g at 22 days old and 2.556 g at 43 days old were used in each experiment and allotted to a completely randomized experimental design, with six treatments, six replicates and 25 birds by experimental unit. The treatments consisted of six different synthetic lysine levels, according to the phase and the fixed ratio. Minimum nutrition requirements, except lysine and met + cys, were met. Feed intake, body weight gain, feed gain ratio, carcass yield and the prime cuts yield were evaluated. The lysine requirements were estimated by the regression models. Considering the performance data, the nutritional requirements of total lysine were of 1.140% for maximum performance, in the period from 22 to 42 days old, and of 1.024% for maximum performance and carcass and breast yield, in the period from 43 to 49 days old.
Levels of lysine for broilers in the periods from 22 to 42 and from 43 to 49 days old, maintaining the methionine + cystine ratio
Júnior,Valene da Silva Amarante and Costa,Fernando Guilherme Perazzo and Barros,Leilane da Rocha and Nascimento,Germano Augusto Jerônimo do and Brandão,Patrícia Araújo and Silva,José Humberto Vilar da and Pereira,Walter Esfrain and Nunes,Ricardo Vianna and Costa,Janaine Sena da and Ribeiro,Marcelo Luís Gomes. Levels of lysine for broilers in the periods from 22 to 42 and from 43 to 49 days old, maintaining the methionine + cystine ratio. R. Bras. Zootec. [online]. 2005, vol.34, 4, [cited 2026-04-24], pp.1188-1194. Available from: <https://rbz.org.br/article/levels-of-lysine-for-broilers-in-the-periods-from-22-to-42-and-from-43-to-49-days-old-maintaining-the-methionine-cystine-ratio/>. ISSN 1516-3598. https://doi.org/10.1590/S1516-35982005000400013.
Júnior,Valene da Silva Amarante; Costa,Fernando Guilherme Perazzo; Barros,Leilane da Rocha; Nascimento,Germano Augusto Jerônimo do; Brandão,Patrícia Araújo; Silva,José Humberto Vilar da; Pereira,Walter Esfrain; Nunes,Ricardo Vianna; Costa,Janaine Sena da; Ribeiro,Marcelo Luís Gomes. Levels of lysine for broilers in the periods from 22 to 42 and from 43 to 49 days old, maintaining the methionine + cystine ratio. R. Bras. Zootec., v.34, 4, p. 1188-1194. Aug. 2005. Available from: <https://rbz.org.br/article/levels-of-lysine-for-broilers-in-the-periods-from-22-to-42-and-from-43-to-49-days-old-maintaining-the-methionine-cystine-ratio/>. acess on 24 Apr. 2026. https://doi.org/10.1590/S1516-35982005000400013.
Júnior,Valene da Silva Amarante, & Costa,Fernando Guilherme Perazzo, & Barros,Leilane da Rocha, & Nascimento,Germano Augusto Jerônimo do, & Brandão,Patrícia Araújo, & Silva,José Humberto Vilar da, & Pereira,Walter Esfrain, & Nunes,Ricardo Vianna, & Costa,Janaine Sena da, & Ribeiro,Marcelo Luís Gomes. (2005). Levels of lysine for broilers in the periods from 22 to 42 and from 43 to 49 days old, maintaining the methionine + cystine ratio. R. Bras. Zootec., 34(4) , 1188-1194. https://doi.org/10.1590/S1516-35982005000400013.
JúniorValene da Silva Amarante, CostaFernando Guilherme Perazzo, BarrosLeilane da Rocha, NascimentoGermano Augusto Jerônimo do, BrandãoPatrícia Araújo, SilvaJosé Humberto Vilar da, PereiraWalter Esfrain, NunesRicardo Vianna, CostaJanaine Sena da, RibeiroMarcelo Luís Gomes. Levels of lysine for broilers in the periods from 22 to 42 and from 43 to 49 days old, maintaining the methionine + cystine ratio. R. Bras. Zootec. [Internet]. 2005 Aug [cited 2026 Apr 24]; 34(4): 1188-1194. Available from: https://rbz.org.br/article/levels-of-lysine-for-broilers-in-the-periods-from-22-to-42-and-from-43-to-49-days-old-maintaining-the-methionine-cystine-ratio/. https://doi.org/10.1590/S1516-35982005000400013.
Figure 6
Differential abundance for the species Faecalibacterium prausnitzii (A) and Megamonas funiformis (B).
