Relação ideal dos aminoácidos essenciais para mantença, crescimento e produção de aves
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Data
2016-02-26
Autores
Dorigam, Juliano Cesar de Paula [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O tradicional método dose-resposta usado para determinar a relação ideal dos aminoácidos essenciais (IAAR) tem sido considerado muito oneroso, principalmente quando reprodutores são usados, pois é necessário um ensaio para cada aminoácido essencial (EAA). Por outro lado, o método da deleção tem sido considerado um meio rápido e prático para determinar a IAAR, pois apenas um ensaio é necessário. Dessa forma, o objetivo desta tese foi determinar a relação ideal dos aminoácidos essenciais para reprodutores (matrizes e galos) e frangos de corte utilizando o método da deleção. O primeiro estudo teve como objetivo estimar o perfil de aminoácidos essenciais e a relação ideal para a mantença de aves pelo método da deleção. Um ensaio de balanço de nitrogênio foi realizado utilizando 198 galos adultos, alojados individualmente em gaiolas metabólicas. Os tratamentos foram 33 dietas purificadas sendo 11 dietas com uma mistura de aminoácidos que fornecem alto consumo de proteínas de 500 mg N /BWkg0.75 por dia, 11 dietas que fornecem a ingestão média de proteína de 250 mg N /BWkg0.75 por dia (em cada dieta um aminoácido testado foi reduzido a 50%) e 11 dietas proporcionando baixa ingestão de proteína de 125 mg de N /BWkg0.75 por dia (formulada omitindo o aminoácido testado). Cada tratamento teve seis repetições. Após 48 h de jejum, recebendo água mais sacarose, os galos foram alimentados com 40 g das dietas por tubo, uma vez por dia, durante três dias. As excretas foram coletadas no prazo de 72 horas após a primeira ingestão. As dietas e as excretas foram analisadas quanto ao teor de nitrogênio. Para cada um dos aminoácidos estudados, uma regressão linear foi ajustada entre balanço de nitrogênio e ingestão do aminoácido. As exigências de mantença foram estimadas como a ingestão de aminoácidos para manter o equilíbrio de nitrogênio igual a zero. As exigências diárias dos aminoácidos para mantença foram estimadas em: Lys 11, Met 29, Thr 23, Trp 5, Arg 50, Val 29, His 6, Gly 54, Phe 49, Leu 78 e Ile 21 mg /BWkg0.75 por dia. Portanto, concluiu-se que a proporção de aminoácidos para mantença seria Lys 100, Met 276, Thr 220, Trp 48, Arg 467, Val 275, His 60, Gly 511, Phe 467, Leu 735 e Ile 198% independente da unidade usada. O perfil de aminoácidos essenciais e a relação ideal para mantença das aves, estimado neste estudo, contribui para a melhoria do modelo fatorial para estimar exigências de aminoácidos essenciais para aves. No segundo estudo, duas abordagens utilizando o método da deleção dos aminoácidos (AA), um com abate comparativo e outro com balanço de nitrogênio, foram utilizados para reavaliar as pressupostas relações ideais entre os aminoácidos essenciais (EAA): lisina (Lys), metionina+cistina (Met+Cys), treonina (Thr), triptofano (Trp), arginina (Arg), valina (Val), isoleucina (Ile), leucina (Leu), fenilalanina + tirosina (Phe+Tyr), glicina + serina (Gly+Ser), e histidina (His) para o crescimento de frangos de corte do genótipo Cobb 500 durante três períodos (I: 6 a 21, II: 22 a 37, e III: 38-53 d). Por ensaio, 120 frangos, machos, foram alojados em gaiolas metabólicas para avaliação dos dados de balanço de nitrogênio e eficiência de utilização de cada AA. Uma dieta balanceada em AA (BD) foi formulada de acordo com as recomendações das tabelas brasileiras (Rostagno et al., 2011) para a proteína ideal de frangos de corte em crescimento. As dietas com diferentes AAs limitantes foram criadas pela deleção da BD com amido de milho para alcançar 0,70 do nível de AA como BD e resuplementado com AA cristalinos, exceto o AA em estudo. As dietas com a deleção de cada AA levaram a uma piora significativa na utilização da proteína e indicou posição limitante válida destes AA. Além disso, no início e no final do ensaio, um grupo de aves com peso médio de cada repetição foi abatida sem perda de sangue para determinar a deposição de nitrogênio pela técnica do abate comparativo. O valor médio das relações ideais dos onze EAA testados, determinadas pelo abate comparativo, nos três períodos foram: Lys 100, Met+Cys 65, Thr 66, Trp 17, Arg 108, Val 79, Ile 61, Leu 122, Phe+Tyr 128, Gly+Ser 155, e His 41. Com base nos dados de eficiência dos AA observados, as relações ideais determinadas pelo balanço de nitrogênio foram: Lys 100, Met+Cys 72, Thr 65, Trp 17, Arg 106, Val 76, Ile 67, Leu 107, Phe + Tyr 115, Gly+Ser 137, e His 35. Existem algumas diferenças entre os resultados obtidos pelos dois métodos (Louvain e Goettingen), mas o método de Goettingen apresentou resultados mais condizentes com a literatura e menor variação nos resultados. No terceiro estudo, o objetivo foi determinar os parâmetros do modelo para a máxima retenção de nitrogênio (NRmaxT), a exigência de mantença de nitrogênio (NMR) e a eficiência de utilização de lisina (bc-1) para determinar a exigência de lisina (Lys) de aves reprodutoras pesadas. Os ensaios de balanço de nitrogênio foram realizados em dois períodos (I: 31-35 semanas e II: 46-50 semanas). Foram utilizados sete tratamentos com oito repetições e uma ave por gaiola; os tratamentos consistiram de sete dietas com níveis de proteína variando de 58,8-311,9 g/kg de ração, com a Lys sendo limitante na proteína dietética (c = 3,91 g de Lys em 100 g de CP). Para cada período, os dados de nitrogênio ingerido (NI), nitrogênio excretado (NEX), nitrogênio na massa de ovos (NEM), nitrogênio depositado (ND, ND = NI-NEX) e nitrogênio retido (NR, NR = ND + NEM + NMR) foram obtidos num ensaio de balanço de nitrogênio de 25 dias. A NMR foi calculada pela relação exponencial entre NEX e NI. O NRmaxT e o b (inclinação relacionadas com a qualidade da proteína) foram estimados pelo ajuste exponencial entre NR e NI. Foi obtido o bc-1 dividindo b por c. Com base no teste da razão de verossimilhança para os parâmetros do modelo, os valores obtidos foram 255 mg /BWkg0.67 para NMR, 0,000117 para b e 1684 mg/BWkg0.67 (período I) e 1484 mg/BWkg0.67 (período II) para NRmaxT. As ingestões de Lys foram estimadas pela função Lys = (ln (NRmaxT) -ln (NRmaxT-NR)):(16 × bc-1)) função, que resultou nas ingestões de Lys de 915 e 876 mg/d para matrizes nos períodos I e II, respectivamente. O estudo conclui que a exigência Lys ideal esta de acordo com os dados da literatura, mas as recomendações podem ser adaptadas de acordo com o consumo de ração, a deposição de proteína desejada e a eficiência de utilização do AA na dieta. No quarto estudo, o objetivo foi aplicar os dados de eficiência (bc-1) dos AAs lisina (Lys), metionina+cistina (Met+Cys), treonina (Thr), triptofano (trp), arginina (Arg), valina (Val), isoleucina (Ile), leucina (Leu), fenilalanina+tirosina (Phe+Tyr), glicina + serina (Gli+Ser) e histidina (His) para obter uma relação ideal de AA (IAAR) para matrizes. Os ensaios de balanço de nitrogênio foram realizados de 31 a 35 semanas e de 46 a 50 semanas. Foram utilizados doze tratamentos com oito repetições e uma ave por gaiola. Uma dieta balanceada (BD) foi formulada para atender a IAAR e a exigência de outros nutrientes para matrizes. As dietas limitantes foram formuladas diluindo BD com amido de milho e resuplementados com AAs cristalinos e outros ingredientes para alimentação animal, com exceção do AA em estudo. Em cada período, os dados de nitrogênio ingerido (NI), nitrogênio excretado (NEX), nitrogênio na massa de ovo (NEM), nitrogênio depositado (ND, ND = NI-NEX) e nitrogênio retido (NR, NR = ND + NEM + NMR) foram obtidos em um ensaio de 25 dias. Os valores de qualidade de proteínas (b) foram estimadas por b = (ln (NRmaxT) -ln (NRmaxT-NR)) : (NI)), onde NRmaxT é o potencial para a retenção máxima de nitrogênio de matrizes. Os valores de bc-1 foram obtidos dividindo b pela concentração do AA na dieta (c, g AA / 16 g de N). A posição limitante de cada AA foi confirmada e os valores de bc-1 foram usados para obter um IAAR média: Lys (100), Met + Cys (83), Trp (24), Thr (81), Arg (114), Val (90), Ile (93), Leu (105), Phe + Tyr (109), Gly + Ser (95), e His (35). A IAAR estava de acordo com a recomendação da literatura, validando este procedimento alternativo para a determinação da IAAR para aves reprodutoras pesadas. Finalmente, o objetivo deste quinto estudo foi aplicar o método da deleção para obter uma IAAR para aves reprodutoras pesadas. Os ensaios de balanço de nitrogênio foram realizados de 31 a 35 semanas e de 46 a 50 semanas. Foram utilizados doze tratamentos com oito repetições e uma ave por gaiola. Uma dieta balanceada (BD) foi formulada para atender rigorosamente a IAAR e a exigência de outros nutrientes. As dietas limitantes foram formuladas diluindo BD com amido de milho e resuplementados com aminoácidos cristalinos (EAA) e outros ingredientes para alimentação animal, com exceção do EAA em estudo. Cada ensaio durou 25 dias. As perdas de penas, a produção de ovos e o peso do ovo foram registrados diariamente e as amostras foram armazenadas para determinar NEM e o nitrogênio nas perdas de penas (NDFL), respectivamente. No início e no final de cada período, um grupo de matrizes foi abatido para determinar o nitrogênio depositado no corpo (NDB) e penas (NDF). A NR foi calculada como a soma de NDB, NDF, NDFL, NEM, e a exigência de nitrogênio para mantença (NMR = 255 mg /BWkg0.67 por dia). A redução percentual no NR resultante da deleção de cada EAA em relação à BD e o percentual do AA para excluir a partir da BD foram utilizados para calcular a exigência ótima do AA na dieta. A IAAR média determinada foi: Lis (100), Met + Cys (86), Trp (23), Thr (80), Arg (113), Vai (90), Ile (91), Leu (133), Phe + Tyr (108), Gly+Ser (94), e His (35). A IAAR determinada neste estudo estava de acordo com a recomendação da literatura para frangos de corte, especialmente usando o método de Goettingen, validando o método da deleção para determinar o IAAR. Além disso, o método foi padronizado para matrizes reprodutoras e os resultados deste estudo permitiram atualizar a relação ideal para estas aves. Da mesma forma, o método da deleção para determinar a IAAR de mantença também foi padronizado e o perfil ideal atualizado. Por fim, a padronização destes métodos vai permitir que a pesquisa brasileira usufrua de um procedimento rápido e de baixo custo para estimar e avaliar a IAAR.
The traditional dose-response method used to determine the ideal essential amino acid ratio (IAAR) has been considered too costly, especially when breeders are used, because an assay for each essential amino acid (EAA) is necessary. On the other hand, the deletion method has been considered a quick and practical way to determine the IAAR, because only one assay is required. Thus, the aim of this thesis was to determine the optimal ratio of essential amino acids for breeders (broiler breeder hens and roosters) and broilers using the deletion method. The first study aimed to estimate the essential amino acid profile and the ideal ratio for maintenance of poultry by deletion method. A nitrogen (N) balance trial was conducted using 198 adult roosters, housed individually in metabolic cages. The treatments were 33 purified diets being 11 diets with an EAA mixture providing high protein intake of 500 mg N/BWkg0.75 per day, 11 diets providing medium protein intake of 250 mg N/BWkg0.75 per day (in each diet one EAA tested was reduced 50%) and 11 diets providing low protein intake of 125 mg N/BWkg0.75 per day (made by omitting the EAA tested). Each treatment had six replicates. After 48 h of fasting receiving water plus sucrose, the roosters were fed 40 g of the diets by tube once a day for three days. The excreta were collected within 72 h after the first feeding. The diets and excreta were analyzed for nitrogen content. For each EAA studied, a linear regression was fitted by N balance and EAA intake. The maintenance requirements were estimated as the EAA intake to maintain the N balance equal to zero. The daily EAA requirements for maintenance were estimated to be: Lys 11, Met 29, Thr 23, Trp 5, Arg 50, Val 29, His 6, Gly 54, Phe 49, Leu 78 and Ile 21 mg/BWkg0.75 per day. Therefore, the EAA ratio for maintenance was concluded to be Lys 100, Met 276, Thr 220, Trp 48, Arg 467, Val 275, His 60, Gly 511, Phe 467, Leu 735 and Ile 198% independent of the scale. The EAA profile and the ideal ratio for maintenance of poultry estimated in this study contribute to improve factorial model for estimating EAA requirements for poultry. In the second study, two approaches using amino acid deletion method, one with comparative slaughter and another with N balance, were used to re-evaluate the actual assumptions of ideal ratios between the EAA: lysine (Lys), methionine+cystine (Met+Cys), threonine (Thr), tryptophan (Trp), arginine (Arg), valine (Val), isoleucine (Ile), leucine (Leu), phenylalanine+tyrosine (Phe+Tyr), glycine+serine (Gly+Ser), and histidine (His) for growing broilers of Cobb 500 genotype during three periods (I: 6 to 21, II: 22 to 37, and III: 38 to 53 d). Per trial, 120 male chickens were housed in metabolic cages for assessment of individual N-balance and AA efficiency data. An AA balanced diet (BD) was formulated according to recommendations of Brazilian tables (Rostagno et al., 2011) for the ideal protein in growing broilers. The diets with different limiting AAs were created by dilution of BD with corn starch to achieve 0.70 of the AA level in BD and supplemented with crystalline AAs, except the AA under study. The AA diluted diets led to significant impairment of protein utilization and indicated valid limiting position of these AAs. Also, at start and the end of the trial a group of birds with mean body weight of each replicate was killed with no blood loss to determine nitrogen deposition by comparative slaughter technique. The mean value of the optimum ratios of the eleven tested EAAs determined by comparative slaughter in the three periods are: Lys100, Met+Cys 65, Thr 66, Trp 17, Arg 108, Val 79, Ile 61, Leu 122, Phe+Tyr 128, Gly+Ser 155, and His 41. Based on observed AA efficiency data, the optimum ratios determined by nitrogen balance are: Lys 100, Met+Cys 72, Thr 65, Trp 17, Arg 106, Val 76, Ile 67, Leu 107, Phe+Tyr 115, Gly+Ser 137, and His 35. There are some differences among the results obtained by the two methods (Louvain and Goettingen approach), but the Goettingen approach provided result in accordance with the literature and less variation in the results. The third study aimed to determine the model parameters for maximum nitrogen retention (NRmaxT), nitrogen maintenance requirement (NMR) and the efficiency of lysine utilization (bc-1) to determine the lysine (Lys) requirements of broiler breeder hens. The N balance trials were performed in two periods (I: 31-35 wks and II: 46-50 wks). Seven treatments were used with eight replicates and one hen per cage; the treatments consisted of seven diets with protein levels ranging from 58.8 to 311.9 g/kg of feed, with Lys being limiting in the dietary protein (c = 3.91 g of Lys in 100 g of CP). For each period, the data of nitrogen intake (NI), nitrogen excretion (NEX), nitrogen in egg mass (NEM), nitrogen deposition (ND, ND=NI-NEX) and nitrogen retention (NR, NR=ND+NEM+NMR) were obtained in a balance trial of 25 days. The NMR was calculated by the exponential relationship between NEX and NI. The NRmaxT and b (slope related to protein quality) were estimated by the exponential fit between NR and NI. The bc-1 was obtained dividing b by c. Based on the likelihood ratio test for the model parameters, the obtained values were 255 mg/BWkg0.67 for NMR, 0.000117 for b and 1684 mg/BWkg0.67 (period I) and 1484 mg/BWkg0.67 (period II) for NRmaxT. The Lys intakes were estimated by the function Lys = (ln(NRmaxT)-ln(NRmaxT-NR)):(16×bc-1)), which resulted in the Lys intakes of 915 and 876 mg/d for breeder hens in the periods I and II, respectively. The current study concludes that the optimal Lys requirement is in range with literature data, but the recommendations can be adapted according to feed intake, aimed protein deposition and dietary AA efficiency. The fourth study aimed to apply the individual AA efficiency data (bc-1) for lysine (Lys), methionine+cystine (Met+Cys), threonine (Thr), tryptophan (Trp), arginine (Arg), valine (Val), isoleucine (Ile), leucine (Leu), phenylalanine+tyrosine (Phe+Tyr), glycine+serine (Gly+Ser) and histidine (His) to derive an ideal AA ratio (IAAR) for breeder hens. N-balance trials were performed from 31 to 35 wks and from 46 to 50 wks. Twelve treatments with eight replicates and one hen per cage were used. A balanced diet (BD) was formulated to meet the IAAR and the requirement of other nutrients for breeder hens. The limiting diets were formulated diluting BD with corn starch and refilled with crystalline AAs and other feed ingredients, except for the AA under study. In each period, the data of N-intake (NI), N-excretion (NEX), N in egg mass (NEM), N-deposition (ND, ND=NI-NEX) and N-retention (NR, NR=ND+NEM+NMR) were obtained in a balance trial of 25 days. The b values (protein quality) were estimated by b = (ln(NRmaxT)-ln(NRmaxT-NR)):(NI)), where NRmaxT is the potential for maximum nitrogen retention of breeder hens. The bc-1 values were obtained dividing b by the dietary AA concentration (c, g AA/16g N). The limiting position of each AA was confirmed and the bc-1 values were used to obtain an average IAAR: Lys (100), Met+Cys (83), Trp (24), Thr (81), Arg (114), Val (90), Ile (93), Leu (105), Phe+Tyr (109), Gly+Ser (95), and His (35). The IAAR was in the line with the recommendation from the literature, validating this alternative procedure for predicting dietary IAAR for broiler breeder hens. Finally, the aim of the fifith study was to apply the deletion method to derive an IAAR for broiler breeder hens. The nitrogen balance trials were performed from 31 to 35 wks and from 46 to 50 wks. Twelve treatments with eight replicates and one hen per cage were used. A balanced diet (BD) was formulated to strictly meet the IAAR and the requirement of other nutrients. The limiting diets were formulated diluting BD with corn starch and refilled with crystalline amino acids (AA) and other feed ingredients, except for the AA under study. Each feeding trial lasted 25 days. The feather losses, egg production and egg weight were recorded daily and the samples were stored to further determine NEM and nitrogen in feather losses (NDFL), respectively. At the start and the end of each period, a group of breeder hens were slaughtered to further determine nitrogen deposition in the body (NDB) and feathers (NDF). The NR was calculated as the sum of NDB, NDF, NDFL, NEM, and the nitrogen maintenance requirement (NMR=255 mg/BWkg0.67 per day). The percent reduction in NR resulting from the individual AA deletions relative to BD and the percent of the AA to delete from the BD were used to calculate the optimum in-feed AA requirement. The average IAAR determined was: Lys (100), Met+Cys (86), Trp (23), Thr (80), Arg (113), Val (90), Ile (91), Leu (133), Phe+Tyr (108), Gly+Ser (94), and His (35). The IAAR determined in this study corroborate with the recommendations for broilers in the literature, particularly when using the Goettingen approach, validating the deletion method for determining the IAAR. In addition, the method has been standardized for broiler breeder hens and the results of this study allowed updating the ideal ratio for these birds. Likewise, the deletion method for determining the IAAR for maintenance was also standardized and the ideal profile updated. Finally, the standardization of these methods will allow Brazilian research enjoy a rapid and low-cost procedure to estimate and evaluate the IAARs.
The traditional dose-response method used to determine the ideal essential amino acid ratio (IAAR) has been considered too costly, especially when breeders are used, because an assay for each essential amino acid (EAA) is necessary. On the other hand, the deletion method has been considered a quick and practical way to determine the IAAR, because only one assay is required. Thus, the aim of this thesis was to determine the optimal ratio of essential amino acids for breeders (broiler breeder hens and roosters) and broilers using the deletion method. The first study aimed to estimate the essential amino acid profile and the ideal ratio for maintenance of poultry by deletion method. A nitrogen (N) balance trial was conducted using 198 adult roosters, housed individually in metabolic cages. The treatments were 33 purified diets being 11 diets with an EAA mixture providing high protein intake of 500 mg N/BWkg0.75 per day, 11 diets providing medium protein intake of 250 mg N/BWkg0.75 per day (in each diet one EAA tested was reduced 50%) and 11 diets providing low protein intake of 125 mg N/BWkg0.75 per day (made by omitting the EAA tested). Each treatment had six replicates. After 48 h of fasting receiving water plus sucrose, the roosters were fed 40 g of the diets by tube once a day for three days. The excreta were collected within 72 h after the first feeding. The diets and excreta were analyzed for nitrogen content. For each EAA studied, a linear regression was fitted by N balance and EAA intake. The maintenance requirements were estimated as the EAA intake to maintain the N balance equal to zero. The daily EAA requirements for maintenance were estimated to be: Lys 11, Met 29, Thr 23, Trp 5, Arg 50, Val 29, His 6, Gly 54, Phe 49, Leu 78 and Ile 21 mg/BWkg0.75 per day. Therefore, the EAA ratio for maintenance was concluded to be Lys 100, Met 276, Thr 220, Trp 48, Arg 467, Val 275, His 60, Gly 511, Phe 467, Leu 735 and Ile 198% independent of the scale. The EAA profile and the ideal ratio for maintenance of poultry estimated in this study contribute to improve factorial model for estimating EAA requirements for poultry. In the second study, two approaches using amino acid deletion method, one with comparative slaughter and another with N balance, were used to re-evaluate the actual assumptions of ideal ratios between the EAA: lysine (Lys), methionine+cystine (Met+Cys), threonine (Thr), tryptophan (Trp), arginine (Arg), valine (Val), isoleucine (Ile), leucine (Leu), phenylalanine+tyrosine (Phe+Tyr), glycine+serine (Gly+Ser), and histidine (His) for growing broilers of Cobb 500 genotype during three periods (I: 6 to 21, II: 22 to 37, and III: 38 to 53 d). Per trial, 120 male chickens were housed in metabolic cages for assessment of individual N-balance and AA efficiency data. An AA balanced diet (BD) was formulated according to recommendations of Brazilian tables (Rostagno et al., 2011) for the ideal protein in growing broilers. The diets with different limiting AAs were created by dilution of BD with corn starch to achieve 0.70 of the AA level in BD and supplemented with crystalline AAs, except the AA under study. The AA diluted diets led to significant impairment of protein utilization and indicated valid limiting position of these AAs. Also, at start and the end of the trial a group of birds with mean body weight of each replicate was killed with no blood loss to determine nitrogen deposition by comparative slaughter technique. The mean value of the optimum ratios of the eleven tested EAAs determined by comparative slaughter in the three periods are: Lys100, Met+Cys 65, Thr 66, Trp 17, Arg 108, Val 79, Ile 61, Leu 122, Phe+Tyr 128, Gly+Ser 155, and His 41. Based on observed AA efficiency data, the optimum ratios determined by nitrogen balance are: Lys 100, Met+Cys 72, Thr 65, Trp 17, Arg 106, Val 76, Ile 67, Leu 107, Phe+Tyr 115, Gly+Ser 137, and His 35. There are some differences among the results obtained by the two methods (Louvain and Goettingen approach), but the Goettingen approach provided result in accordance with the literature and less variation in the results. The third study aimed to determine the model parameters for maximum nitrogen retention (NRmaxT), nitrogen maintenance requirement (NMR) and the efficiency of lysine utilization (bc-1) to determine the lysine (Lys) requirements of broiler breeder hens. The N balance trials were performed in two periods (I: 31-35 wks and II: 46-50 wks). Seven treatments were used with eight replicates and one hen per cage; the treatments consisted of seven diets with protein levels ranging from 58.8 to 311.9 g/kg of feed, with Lys being limiting in the dietary protein (c = 3.91 g of Lys in 100 g of CP). For each period, the data of nitrogen intake (NI), nitrogen excretion (NEX), nitrogen in egg mass (NEM), nitrogen deposition (ND, ND=NI-NEX) and nitrogen retention (NR, NR=ND+NEM+NMR) were obtained in a balance trial of 25 days. The NMR was calculated by the exponential relationship between NEX and NI. The NRmaxT and b (slope related to protein quality) were estimated by the exponential fit between NR and NI. The bc-1 was obtained dividing b by c. Based on the likelihood ratio test for the model parameters, the obtained values were 255 mg/BWkg0.67 for NMR, 0.000117 for b and 1684 mg/BWkg0.67 (period I) and 1484 mg/BWkg0.67 (period II) for NRmaxT. The Lys intakes were estimated by the function Lys = (ln(NRmaxT)-ln(NRmaxT-NR)):(16×bc-1)), which resulted in the Lys intakes of 915 and 876 mg/d for breeder hens in the periods I and II, respectively. The current study concludes that the optimal Lys requirement is in range with literature data, but the recommendations can be adapted according to feed intake, aimed protein deposition and dietary AA efficiency. The fourth study aimed to apply the individual AA efficiency data (bc-1) for lysine (Lys), methionine+cystine (Met+Cys), threonine (Thr), tryptophan (Trp), arginine (Arg), valine (Val), isoleucine (Ile), leucine (Leu), phenylalanine+tyrosine (Phe+Tyr), glycine+serine (Gly+Ser) and histidine (His) to derive an ideal AA ratio (IAAR) for breeder hens. N-balance trials were performed from 31 to 35 wks and from 46 to 50 wks. Twelve treatments with eight replicates and one hen per cage were used. A balanced diet (BD) was formulated to meet the IAAR and the requirement of other nutrients for breeder hens. The limiting diets were formulated diluting BD with corn starch and refilled with crystalline AAs and other feed ingredients, except for the AA under study. In each period, the data of N-intake (NI), N-excretion (NEX), N in egg mass (NEM), N-deposition (ND, ND=NI-NEX) and N-retention (NR, NR=ND+NEM+NMR) were obtained in a balance trial of 25 days. The b values (protein quality) were estimated by b = (ln(NRmaxT)-ln(NRmaxT-NR)):(NI)), where NRmaxT is the potential for maximum nitrogen retention of breeder hens. The bc-1 values were obtained dividing b by the dietary AA concentration (c, g AA/16g N). The limiting position of each AA was confirmed and the bc-1 values were used to obtain an average IAAR: Lys (100), Met+Cys (83), Trp (24), Thr (81), Arg (114), Val (90), Ile (93), Leu (105), Phe+Tyr (109), Gly+Ser (95), and His (35). The IAAR was in the line with the recommendation from the literature, validating this alternative procedure for predicting dietary IAAR for broiler breeder hens. Finally, the aim of the fifith study was to apply the deletion method to derive an IAAR for broiler breeder hens. The nitrogen balance trials were performed from 31 to 35 wks and from 46 to 50 wks. Twelve treatments with eight replicates and one hen per cage were used. A balanced diet (BD) was formulated to strictly meet the IAAR and the requirement of other nutrients. The limiting diets were formulated diluting BD with corn starch and refilled with crystalline amino acids (AA) and other feed ingredients, except for the AA under study. Each feeding trial lasted 25 days. The feather losses, egg production and egg weight were recorded daily and the samples were stored to further determine NEM and nitrogen in feather losses (NDFL), respectively. At the start and the end of each period, a group of breeder hens were slaughtered to further determine nitrogen deposition in the body (NDB) and feathers (NDF). The NR was calculated as the sum of NDB, NDF, NDFL, NEM, and the nitrogen maintenance requirement (NMR=255 mg/BWkg0.67 per day). The percent reduction in NR resulting from the individual AA deletions relative to BD and the percent of the AA to delete from the BD were used to calculate the optimum in-feed AA requirement. The average IAAR determined was: Lys (100), Met+Cys (86), Trp (23), Thr (80), Arg (113), Val (90), Ile (91), Leu (133), Phe+Tyr (108), Gly+Ser (94), and His (35). The IAAR determined in this study corroborate with the recommendations for broilers in the literature, particularly when using the Goettingen approach, validating the deletion method for determining the IAAR. In addition, the method has been standardized for broiler breeder hens and the results of this study allowed updating the ideal ratio for these birds. Likewise, the deletion method for determining the IAAR for maintenance was also standardized and the ideal profile updated. Finally, the standardization of these methods will allow Brazilian research enjoy a rapid and low-cost procedure to estimate and evaluate the IAARs.
Descrição
Palavras-chave
Aminoácidos, Balanço de nitrogênio, Método da deleção, Relação ideal, Amino acids, Deletion method, Ideal ratio, Nitrogen balance