ABSTRACT. An experiment was conducted to evaluate the effect of diets with reduced energy level content, supplemented with carbohydrase, on broiler performance and the coefficient of metabolizability of nutrients. A total of 720 one-day-old male Cobb-500 chicks were distributed in a completely randomized design, with six treatments, eight repetitions of 15 birds each. The treatments were: (1) a positive control, basal diet to meet the requirements of broiler chickens (PC); (2) a negative control, basal diet with a reduction of 80 kcal kg-1 (NC); (3) NC + alphagalactosydase; (4) NC + xylanase; (5) NC + xylanase and alphagalactosydase, and (6) NC + enzymatic blend (alphagalactosydase, xylanase, pectinase and amylase). The nutrient digestibility was not improved by use of enzymes. At 7 days of age, the broilers which were fed diets supplemented with enzymes showed a lower feed intake (FI) and better feed conversion ratio (FCR) than the broilers fed on PC. Both the NC and enzymatic blend resulted in a worse performance of the broilers at 21, 35 and 42 days old. The use of alphagalactosydase and xylanase, isolated or in combination, in a corn-soybean meal-based diet is effective in improving the growth performance of broilers fed energy-reduced diets.

ABSTRACT Two experiments were carried out to evaluate the effects of digestible valine supplementation in pre-starter and starter diets on the productivity, nutrient metabolizability coefficient (NMC), and immune response of broilers from breeders of different ages. Experiments I and II were conducted with broilers in the pre-starter (1 to 7 days of age) and starter (8 to 21 days of age) phases, respectively. Broilers were fed diets that differed in their digestible valine content. In each trial, 400 male Cobb 500® chicks were randomly housed in a 2 × 4 factorial arrangement with eight treatments and five replicates of 10 birds each. The main effects were breeder age (37 vs. 52 weeks) and the digestible valine level in pre-starter (9.2, 10.2, 11.2, and 12.2 g/kg) and starter (8.3, 9.3, 10.3, and 11.3 g/kg) diets. Productive performance, intestinal histology, and immune response of broilers were evaluated. Supplementation with 11.2 g/kg valine in pre-starter diets improved NMC and increased villus height and villus:crypt ratio in the duodenum, jejunum development, and lymphocyte proliferation in the spleen of broilers at seven days of age, without improving performance (body weight gain, feed intake, and feed conversion ratio). In the starter phase, valine supplementation reduced feed intake but did not affect NMC, intestinal development, or immune response. The present results suggest that the same level of digestible valine should be used in the diet of broilers born to breeders of different ages, and the use of 9.2 and 8.3 g/kg digestible valine in pre-starter and starter diets, respectively, is sufficient to ensure satisfactory broiler performance. However, to improve the duodenum and jejunum development and immune response of broilers in the pre-starter phase, higher digestible valine levels are required.

ABSTRACT. The main purpose of this study was to evaluate the characteristics of eggs produced by Japanese quails fed with guava extract. A total of 400 eggs collected from the quails fed with experimental diets, were distributed in a completely randomized design in factorial arrangement 4 x 4 with main effects including four dietary levels of guava extract (0, 3, 6 and 9 g kg-1) and four storage periods (0, 9, 18 and 27 days) totalizing 16 treatments with five replicates of five eggs. The eggs were produced by Japanese quails, fed with experimental diets. The diets were isonutritive formulated by corn-soybean basis. The eggs were stored for different periods, at the same conditions, to constitute the treatments. The parameters evaluated were egg weight loss (g and %), yolk color, Haugh unit, specific gravity, eggshell thickness and pH of the yolk and albumen. Data were submitted to ANOVA, and means were compared using Scott-Knott test, using α = 0.05. The specific gravity of fresh eggs was better with the use of 6 g kg-1 of guava extract in the diet. The use of 3 g kg-1 of guava extract resulted in smaller eggshell thickness of fresh eggs. The Haugh unit was affected just by the storage periods. The dietary guava extract (3, 6 or 9 g kg-1) increased the pH of albumen in eggs stored for 27 days. The use of 6 g kg-1 of guava extract in quails diet increase the specific gravity in fresh eggs and increase the yolk color when the eggs are stored.

RESUMO Objetivou-se avaliar o efeito do extrato de goiaba em dietas de matrizes de codornas japonesas (Coturnix japonica) sobre o desempenho produtivo e a qualidade dos ovos férteis. O experimento foi realizado na Universidade Federal de Goiás. Foram utilizadas 384 matrizes de codornas Japonesas, distribuídas em 4 tratamentos, com 6 repetições, total de 12 fêmeas e 4 machos em cada repetição. Os tratamentos foram quatro níveis de extrato de goiaba nas rações (0,0%, 0,3%, 0,6% e 0,9%). O extrato de goiaba continha 2,13% de ácido elágico, considerado um princípio antioxidante da goiaba. As rações foram isonutritivas. O período experimental foi de 84 dias. Foi avaliada a produção de ovos, consumo de ração, conversão alimentar, massa de ovos, ganho de peso e qualidade interna e externa dos ovos. Os resultados foram submetidos à análise de variância e de regressão com 5% de probabilidade. A utilização do extrato de goiaba não influenciou a produção de ovos, o consumo de ração, a conversão alimentar e a massa de ovos. A altura de gema e albúmen, a unidade Haugh e o índice de gema e de albúmen diminuíram linearmente à medida em que os níveis de extrato de goiaba na ração aumentaram. O diâmetro do albúmen foi maior com 0,48% de extrato de goiaba na ração. A coloração da gema foi influenciada pela utilização do extrato, apresentando coloração mais escura com 0,498% de extrato de goiaba na ração. Conclui-se que o extrato de goiaba não melhora o desempenho e qualidade dos ovos de codornas japonesas.

SUMMARY The aim of this study was to evaluate the guava extract as an antioxidant additive in diets of Japanese quail breeders on the performance and egg’s quality. The experiment was conducted at University Federal of Goias. A total of 384 Japanese quail breeders were used, distributed in four treatments, with six replicates, with a total of 12 females and four males in each replicate. The treatments were performed with four levels of guava extract in the diets (0.0%, 0.3%, 0.6% and 0.9%). The guava extract contained the ellagic acid, considered the guava antioxidant active principle. The diets were isonutritive. Feed and water were offered ad libitum. The experimental period was 84 days. Egg production, feed intake, feed conversion ratio, egg mass, body weight variation and egg quality were evaluated. The results were submitted to analysis of variance and regression analysis. The adopted probability was 5%. Egg production, feed intake, feed conversion ratio and egg mass were not influenced by the use of guava extract. The yolk and albumen height, the Haugh Unit and the yolk and albumen index decreased linearly as the levels of guava extract in the diet increased. The diameter of the albumen was higher with the use of 0.48% of guava extract in the diet. The yolk color was affected by the guava extract, presenting a darker color with 0.50% of guava extract in the diet. It was concluded that the guava extract used as an antioxidant additive does not improve the performance and egg quality of Japanese quails.

ABSTRACT An experiment was conducted aiming to evaluate the effect of different levels of crude protein, based on the ideal protein concept and two rearing systems, on productive performance of brown laying hens. A total of 400 Hisex Brown laying hens between 30 and 45 weeks of age were distributed in a completely randomized design and a 2×4 factorial arrangement, with main effects including two rearing systems (cage and floor) and levels of crude protein (140, 150, 160, and 180 g kg−1), totalizing eight treatments. Five replicates with 10 birds each were used per experimental unit. The following parameters were evaluated: egg production, feed intake, body weight gain, feed conversion ratio, and quality traits such as dirty, cracked, or broken eggs. No interaction effect was observed between dietary protein levels and rearing systems for body weight gain, feed intake, egg production, egg weight, and feed conversion ratio. Feed intake and egg production were higher in the floor rearing system. Feed conversion ratio (kg/dz) was improved in birds reared in the cage system. The rate of cracked and broken eggs was higher in the cage system. The layers reared in the floor system produced a higher percentage of dirty eggs. The dietary protein level did not affect the evaluated parameters. Thus, we conclude that a floor rearing system is an option for layers, and the dietary protein level can be reduced up to 140 g kg−1 for Hisex Brown hens from 30 to 45 weeks of age.

Resumo Realizou-se um experimento objetivando avaliar a utilização de Neem como antimicrobiano em rações de frangos de corte. Foram utilizados 240 pintos de corte, Cobb, com 1 dia de idade, distribuídos em delineamento inteiramente casualizado, 4 tratamentos, 6 repetições, 10 aves por unidade experimental, o período experimental foi de 21 dias. Os tratamentos consistiram: dieta basal sem inclusão de antimicrobiano; dieta com 0,05% de tilosina; dieta com 0,05% e 0,1% de Neem. Avaliou-se: o desempenho zootécnico, a digestibilidade da ração, contagem intestinal de Salmonella sp. e Escherichia coli, e o desenvolvimento dos órgãos linfoides. Dados de desempenho e metabolização dos nutrientes da ração foram submetidos à ANOVA, médias comparadas pelo teste Tukey, adotou-se α=0,05. Dados de contagem de E. coli foram analisados pelo teste de Kruskal-Wallis. O Neem não influenciou as variáveis de desempenho. O coeficiente de metabolizabilidade da matéria seca e extrato etéreo da ração foi melhor com utilização de tilosina (P<0,05). Não se observou crescimento de Salmonella durante o período experimental. A utilização de Neem não reduziu a população de E. coli, e não influenciou no peso dos órgãos linfoides. A utilização do Neem não afetou o desempenho, digestibilidade e microbiota intestinal das aves até 21 dias.

Abstract In the present work, we carried out an experiment aiming at evaluating the use of Neem as an antimicrobial substance in the feeds of broiler chickens. We used 240 one-day-old Cobb broiler chicks distributed in an entirely casual design, with 4 treatments, 6 repetitions and 10 birds per experimental unit, during a 21-day experimental period. Treatments consisted of a basal diet with no antimicrobial inclusion, a diet with 0.05% of tylosin, and a diet with 0.05% and 0.1% of Neem. Parameters evaluated were zootechnical performance, feed digestibility, intestinal count of Salmonella sp. and Escherichia coli, and the development of lymphoid organs. Data on the performance and metabolization of nutrients were subjected to an ANOVA and averages were compared with a post-hoc Tukey test considering α=0.05. Data on E. coli counts were analyzed with a Kruskal-Wallis test. Neem did not influence performance variables. The metabolization coefficient of dry matter and feed ethereal extract was better with tylosin (P<0.05). No growth of Salmonella was observed during the experiment. The use of Neem did not reduce E. coli population and had no influence on lymphoid organs' weight. Therefore, Neem had no effect on the performance, digestibility and intestinal microbiota of birds up to 21 days old.

RESUMO Objetivou-se avaliar a utilização de óleo de copaíba ou sucupira na ração de frangos de corte, sobre o desempenho e saúde intestinal. Foram utilizados 600 pintos de corte machos, da linhagem Cobb500 com um dia de idade, distribuídos em delineamento inteiramente casualizado, com quatro tratamentos e seis repetições com 25 aves cada. Com o objetivo de aumentar o desafio, as aves foram criadas sobre cama reutilizada. Os tratamentos consistiram de: ração controle; ração com antibiótico melhorador de desempenho avilamicina; ração com 2.000 mg/kg de óleo de copaíba e ração com 500 mg/kg de óleo sucupira. Os dados foram submetidos à análise de variância e teste Tukey (5%). A adição de 500 mg/kg do óleo de sucupira resultou em queda do desempenho das aves no período de 21, 33 e 40 dias de idade, já a adição do óleo de copaíba proporcionou resultados de desempenho semelhantes ao antibiótico. A suplementação com óleo de copaíba ou sucupira não promoveu alterações no epitélio intestinal dos frangos avaliados. A adição do óleo de sucupira foi prejudicial ao desempenho das aves. O óleo de copaíba pode ser utilizado em dietas para frangos como melhorador de desempenho.

SUMMARY The aim of this study was to evaluate the effect of supplemental copaiba or sucupira oils on broiler performance and intestinal health. A total of 600 one-day old Cobb 500 male broilers were distributed in a completely randomized design with four treatments and six replicates with 25 broilers each. To increase the health challenge, the broilers were reared on reused litter. The treatments consisted of: control diet; diet with a performance enhancing antibiotic (avilamycin); diet with 2,000 mg/kg copaiba oil and a diet with 500 mg/kg sucupira oil. Data were submitted to analysis of variance and Tukey test (5%). The addition of sucupira oil at 500 mg/kg decreased broiler performance at 21, 33, and 40 days of age, whereas the addition of copaiba oil resulted in similar performance relative to the antibiotic. Dietary supplementation of copaiba or sucupira oils did not change the intestinal epithelium of broilers. The addition of sucupira oil negatively affected broiler performance. Copaiba oil can be used in broiler diets as a performance enhancer.

ABSTRACT This work aimed to investigate the antioxidant capacity of the guava agroindustrial waste as a functional additive in broiler feed to improve the performance and meat quality of boilers. The experiment was conducted in a completely randomized design, consisting of four treatments and six replicates with 12 birds. Treatments included different levels of guava byproduct in the feed: 0, 0.5, 1.0, and 1.5%. We evaluated the performance of broilers at 7 and 21 days old. At 21 days old, two birds from each experimental unit were euthanized for intestine histologic evaluation (duodenum, jejunum, and ileum) and breast and deboned thigh samples were collected for analyzes of pH, colorimetry (L*, a*, and b*), and thiobarbituric reactive substances (TBARS). The use of guava byproduct in the diet at 7 days old did not affect feed intake and feed conversion of the birds. However, the body weight and weight gain increased linearly with the inclusion of the byproduct. At 21 days old, the guava byproduct did not depress the performance of birds. There was no effect of treatments on villus height, crypt depth, and villus:crypt ratio of the duodenum and jejunum of the birds. The inclusion of guava byproduct resulted in lower crypt depth and linear increase in villus:crypt ratio of the ileum. There was no significant difference in pH and colorimetry of the breast and thigh. With increasing inclusion of byproduct, TBARS value was reduced to 0.72%, indicating greater lipid stability in thigh meat in this inclusion amount. Guava byproduct can be used as an alternative antioxidant additive in broiler feed because it does not depress the productive performance and improves thigh meat quality of boilers.

ABSTRACT In this study, we evaluated the effects of substitution of partial and total spray-dried blood plasma (BP) with soy protein concentrate (SPC) in the diet of post-weaning piglets on their performance, intestinal histomorphometry, and blood parameters. Fifty-four castrated male piglets, weaned at an average age of 21 days and an initial average weight of 7.01±0.294 kg, were distributed in a completely randomized block design, with three diets (0%SPC-5%BP, 2.5%SPC-2.5%BP, and 5%SPC-0%BP), six replicates, and three piglets per experimental unit. The experimental feeds were formulated to meet the requirements of the piglets at 21-32 and 33-42 days of age (pre-starter diet) and 43-66 days of age (starter diet). From 21 to 32 and 21 to 42 days of age, daily feed intake, daily weight gain, and final weight of the animals were higher in the group fed 2.5%SPC-2.5%BP and 0%SPC-5%BP. From 21 to 66 days of age, daily weight gain and daily feed intake were higher in the animals fed 2.5%SPC-2.5%BP. No effect was observed on the histomorphometry variables. The total leukocyte count was higher in animals fed 2.5%SPC-2.5%BP and 5%SPC-0%BP and the lymphocyte count was lower in the piglets that received 0%SPC-5%BP. The combined use of soy protein concentrate and spray-dried blood plasma in the feeds of piglets between 21 and 42 days of age improves their productive performance.

Resumo Objetivou-se determinar a exigência de metionina + cistina total para frangas na fase inicial e verificar seu efeito sobre a fase de postura. Na primeira fase experimental, 720 aves (50% Lohmann LSL e 50% Lohmann Brown) com uma semana de idade foram distribuídas em delineamento experimental inteiramente casualizado, em esquema fatorial 5 x 2 (níveis de met + cis e linhagens), com quatro repetições e 18 aves por repetição. Os níveis de met + cis total estudados foram 0,536; 0,616; 0,696; 0,776; e 0,856 %. Ao atingirem 22 semanas de idade, iniciou-se a segunda fase experimental, sendo utilizadas 240 aves (50% Lohmann LSL e 50% Lohmann Brown) provenientes da primeira fase experimental. A ração fornecida às aves nesta fase foi igual para todos os tratamentos. Na fase de produção avaliaram-se os efeitos residuais das dietas fornecidas no período inicial sobre os parâmetros produtivos. As exigências de metionina + cistina recomendadas para aves leves e semipesadas, no período de 1 a 6 semanas de idade, são de 0,778% de met + cis total (correspondendo a 0,700% de met + cis digestível) e 0,739% de met + cis total (correspondendo a 0,665% de met + cis digestível), respectivamente.

Abstract An experiment was carried out to evaluate the requirement of methionine +cystine for growing pullets at starter phase (1 to 6 weeks old) and its effect on the laying phase. In the first experiment, 720 birds (50% Lohmann LSL and 50% Lohmann Brown) at one week of age were distributed on a completely randomized design, 5 x 2 factorial arrangement (levels of met + cys and strain), with four replications and 18 birds each. The levels of total methionine + cystine studied were 0.536; 0.616; 0.696; 0.776; and 0.856 %. At 22 weeks of age, 240 birds were used for the second experimental phase. The diets given to birds at this phase was the same for all the treatments. In the production phase, the residual effects of the experimental diets provided during the initial phase on the production parameters were evaluated. The level of methionine + cystine recommended for white-egg and brown-egg pullets in the period from 1 to 6 weeks of age are 0.778 % of total methionine + cystine (0.700% met + cis digestible) and 0.739% of total methionine + cystine (0.665% of digestible methionine + cystine), respectively.

ABSTRACT Seventy-two barrows were used to evaluate the effects of the use of soy protein concentrate (SPC) in diets of post-weaning piglets on their performance, intestinal histomorphometry, and blood parameters. Piglets were weaned at 21 days of age and distributed in a randomized-block experimental design with four treatments (0, 3, 6, and 9% SPC), six replications, and three piglets per replication. Diets were formulated to meet the requirement of the piglets according to phases of 21 to 32, 33 to 42, and 43 to 66 days of age. Both feed and water were provided ad libitum during the entire experiment. The feed of the phase of 43 to 66 days was based on corn and soybean meal. In the period between 21 and 32 days of age, the use of SPC in the diet did not impact the daily weight gain (DWG) or the daily feed intake (DFI) of the piglets, whereas there was a linear effect on feed conversion (FC), which decreased as the levels of SPC in the feed were increased. In the period between 33 and 42 days of age, a linear effect was observed on FC, which increased as the level of SPC in the feed was increased. In this period, no effects of SPC were observed on DWG or DFI. Inclusion of SPC in the diets does not influence performance, intestinal histomorphometry, or blood parameters of piglets in the period between 21 and 66 days of age.

Resumo Objetivou-se determinar a exigência nutricional de cálcio e a melhor relação cálcio:fósforo em rações para poedeiras leves de 24 a 40 semanas de idade. Foram utilizadas 324 aves Hy-Line W-36, distribuídas em delineamento inteiramente casualizado, esquema fatorial 3x3, sendo três níveis de cálcio (3,9; 4,2 e 4,5 %) e três relações cálcio/fósforo (9,3; 10,53 e 12,12/1), totalizando nove tratamentos, seis repetições e seis aves por unidade experimental. Avaliou-se o desempenho produtivo, a qualidade do ovo, as características ósseas, o balanço de cálcio e fósforo e a mortalidade. Não houve interação (P>0,05) entre os níveis de cálcio e as relações cálcio/fósforo para nenhuma das variáveis, porém os níveis de cálcio promoveram efeito (P<0,05) sobre o peso e porcentagem da casca, cálcio na casca, ovos perdidos, consumo de cálcio e fósforo, cálcio e fósforo na excreta, cálcio e fósforo retido. A relação cálcio/fósforo influenciou significativamente (P<0,05) o consumo de ração, ganho de peso, conversão alimentar, consumo de cálcio e fósforo, fósforo na excreta e fósforo retido. Rações contendo 4,5% de cálcio e relação cálcio:fósforo de 12,12:1, correspondendo ao consumo de cálcio de 3,71 g/ave/dia e de fósforo de 306 mg/ave/dia, garantem desempenho satisfatório em rações para poedeiras leves no período de 24 a 40 semanas.

Abstract The objective of this study was to determine the nutritional requirement for calcium and the best calcium:phosphorus ratio in the diet for laying hens from 24 to 40 weeks of age. 324 Hy-Line W-36 birds were distributed in a completely randomized design in 3x3 factorial scheme, consisting of three levels of calcium (3.9, 4.2, and 4.5%) and three calcium:phosphorus ratios (9.3, 10.53, and 12.12:1) totaling nine treatments, six replicates and six birds each. We evaluated performance, egg quality, bone characteristics, balance of calcium and phosphorus, and mortality. There was no interaction (P> 0.05) between calcium levels and calcium:phosphorus ratio for the variables, but levels of calcium affected (P <0.05) weight and shell percentage, calcium in the shell, lost eggs, consumption of calcium and phosphorus, calcium and phosphorus excretion, and retained calcium and phosphorus. The calcium:phosphorus ratio affected significantly (P <0.05) feed intake, weight gain, feed conversion per dozen eggs, egg mass, calcium and phosphorus intake, phosphorus excretion, and retained phosphorus. Diets containing 4.5% calcium and the calcium:phosphorus ratio of 12,12:1, corresponding to a calcium intake of 3.71 g/hen/day and phosphorus of 306 mg/bird /day, guarantee satisfactory performance in diets for laying hens from 24 to 40 weeks.

Quinhentos frangos de corte machos da linhagem Cobb foram distribuídos em delineamento em blocos casualizados com cinco tratamentos, quarto repetições e 25 aves por unidade experimental para avaliar os efeitos da adição de L-glutamina na dieta das aves sem anticoccidiano e promotor de crescimento. As dietas experimentais continham L-glutamina em diferentes níveis (0,0;5,0;10,0;15.0 e 20,0g/kg). O experimento foi conduzido com frangos de corte de 1 a 42 dias de idade. As variáveis avaliadas foram consumo de ração, conversão alimentar, ganho de peso, mortaliade, coeficientes de digestibilidade da matéria seca, da proteína bruta e do extrato etéreo, rendimento de carcaça e morfometria do intestino delgado. Os dados foram submetidos à análise de regressão polinomial. As médias foram comparadas pelo teste Tukey. - Considerou-se o erro tipo I sendo P < 0,05. O nível de L-glutamina na dieta influenciou a conversão alimentar dos frangos de 1 a 7 dias de idade, sendo melhor com 10,0g/kg L-glutamina. Rendimento de carcaça e coeficientes de digestibilidade não foram afetados pelos níveis de glutamina na dieta. Adição de L-glutamina influenciou a profundidade de cripta do intestino delgado aos 18 e 42 dias de idade. Recomenda-se a adição de 10,0g/kg L-glutamina na dieta pré-inicial das aves.

Five hundred commercial male Cobb broilers were allotted in a randomized blocks design with five treatments, four replicates and 25 chicks per experimental unit in order to evaluate the effects of adding L-glutamine to the diet with no anticoccidial agents and growth promoters. Experimental diets contained L-glutamine at different levels (0.0; 5.0; 10.0; 15.0 or 20.0g/kg), through the experimental period. Experiment was conducted with broiler chicken from 1 to 42 days old. The parameters evaluated were feed intake, feed conversion ratio, body weight gain, mortality, digestibility coefficients of dry matter, crude protein and ether extract, carcass yield and intestinal mucosa structure of small intestine. The data obtained were submitted to polynomial regression analysis. Means were compared using Tukey test.Was considered a type I error set at P < 0.05. The level of L-glutamine in the diet influenced feed conversion ratio of broilers at 1-7 days old, which was improved at 10.0g/kgL glutamine. Carcass yield and digestibility coefficients of the diet were not affected by the levels of glutamine in the diet. Adding L-glutamine influenced crypt depth in small intestine of broilers at 18 and 42 days old. It is recommended the addition of 10.0g/kg L-glutamine to the pre-started diet.

Two-hundred sixteen white laying hens were used to assess the ideal ratio of digestible threonine:lysine in diets for laying hens at 24 to 40 weeks of age. Birds were assigned to a randomized block design, with six treatments, six replicates per treatment and six birds per experimental unit. The cage was used as the blocking criterion. Experimental diets contained different digestible threonine:digestible lysine ratios (65, 70, 75, 80, 85 and 90%) with 142 g/kg of crude protein. Experimental diets were formulated to be isonitrogenous and isocaloric with different contents of L-glutamic acid. Feed intake (g/hen/d), egg production (%), egg weight (g), egg mass (g/hen/d), feed conversion ratio (kg/dozen and kg/kg egg), eggshell weight (g), albumen weight (g), yolk weight (g) and body weight gain (g) were assessed. The maximum egg production was observed at 78% digestible threonine:digestible lysine ratio, while the best values of feed conversion ratio (kg/dozen egg) and feed conversion ratio (kg/kg of egg) were observed at 77.6% and 75%, respectively. Feed intake, egg mass and egg contents (yolk, albumen and eggshell) were not affected by treatments. The estimated digestible threonine:digestible lysine ratio of Hy-Line W36 laying hens at 24 to 40 weeks of age is 78%, corresponding to 5.70 g/kg of dietary digestible threonine.

Two hundred fifty-two Hy-Line W36 laying hens were allotted in a randomized block design with 6 treatments, 7 replicates and 6 hens per experimental unit in order to determine the ideal digestible isoleucine: digestible lysine (Ile:Lys) ratio for laying hens aged 24-40 weeks. Experimental diets contained 5.92, 6.33, 6.73, 7.14, 7.54 and 7.95 g/kg of digestible isoleucine, resulting in different Ile:Lys ratios (0.73:1, 0.78:1, 0.83:1, 0.88:1, 0.93:1 and 0.98:1). Experimental diets were isonitrogenous, with different dietary contents of glutamic acid, and made isocaloric by adjusting the levels of cornstarch. All essential amino acids were provided proportionally to digestible lysine. Feed intake, egg production, egg weight, egg mass, feed conversion ratio per egg mass, feed conversion ratio per dozen eggs, albumen, yolk and eggshell content were assessed. Feed intake, egg production, egg mass and feed conversion ratio were influenced by Ile: Lys ratios quadratically. The egg weight was not affected by Ile: Lys ratio. No differences were observed in the egg quality according to Ile: Lys ratios. The data indicates that the optimum digestible isoleucine: digestible lysine ratio for laying hens aged 24-40 week is 0.84:1, corresponding to the consumption of 681 mg of isoleucine and 811 mg of lysine/hen day-1.