True Amino Acid Digestibility Research Articles

Apparent and true digestibility of protein and amino acid in feedstuffs used in Nile Tilapia feed as determined by the technique of dissection

The objective of this study was to determine the coefficients of apparent and true digestibility of protein and amino acids of five feedstuffs (corn, wheat bran, soybean meal, corn gluten meal and fish meal) in 900 sex-reversed Nile tilapia (Oreochromis niloticus) of the Thai strain during the growth phase, with an initial weight of 315±8.45 g. A total of 750 fish were distributed according to a randomized block design (repetitions in time) into five treatments with six replicates of 25 fish each. The remaining 150 fish were fed a protein-free diet to measure endogenous protein and amino acid losses in order to determine the true digestibility of these components. Each tested diet contained a single protein source, which consisted of one of the evaluated feedstuffs. Digestibility was indirectly estimated using chromic oxide at 0.50% as marker. Digesta was collected from the last 5 cm of the distal intestine (between the ileal-rectal valve and the anus) using the dissection technique. Apparent digestibility coefficients of protein and amino acids were, on average, 74.69 and 73.62% for corn, 73.74 and 72.81% for wheat bran, 86.01 and 84.66% for soybean meal, 85.19 and 84.29% for corn gluten meal, 76.74 and 75.56% for fish meal, respectively. True digestibility coefficients of protein and amino acids were, on average, 85.21 and 83.97% for corn, 84.41 and 83.74% for wheat bran, 87.22 and 87.51% for soybean meal, 87.97 and 87.34% for corn gluten meal, and finally 79.58 and 78.44% for fish meal, respectively.

Prediction of digestible amino acid and true metabolizable energy contents of sorghum grain from total essential amino acids

SUMMARYAccurate information on metabolizable energy and true digestible amino acid (TDAA) content of sorghum grain is important in order to formulate sorghum-based poultry diets accurately. Estimates of ingredient nutritional values using bioassay methods require live birds and special facilities, which are time-consuming and costly. Accordingly, prediction by mathematical models would be of some considerable benefit. Sixty-eight samples of sorghum grain, representing 32 different varieties, were used to test the correlation between TDAA and nitrogen-corrected true metabolizable energy (TMEn) with total essential amino acids. Two methods of multiple linear regressions (MLR) and artificial neural network (ANN) models were used to find the relationship between total amino acids (model inputs) with TDAA and TMEn contents (model outputs) in sorghum grain. The fitness of the models was tested usingR2, mean square (MS) error and bias. There is a strong relationship between total amino acid concentration with both TDAA and TMEn content in sorghum grain. The TDAA and TMEn values were more accurately estimated by ANN model compared to values obtained from the MLR model. TheR2values corresponding to testing and training of the ANN model showed a higher accuracy of prediction than the equation constructed by MLR method. Based on the experimental evidence, it is concluded that the TDAA and TMEn values in sorghum grain can be predicted from total essential amino acids using ANN models. Consequently, this method provides an opportunity to reduce the risk of formulating an unbalanced TDAA diet for poultry.

Justifying phytogenic feed additive matrix values in conjunction with exogenous feed enzymes

SUMMARY Phytogenic feed additives (PFA) are purported to possess antimicrobial properties as well as nutrient-sparing characteristics that may aid in alleviating high diet costs. However, for PFA to assist nutritionists, matrix values must be determined and implemented in practical diet formulation. In experiment 1, we used broiler performance measures to evaluate proposed matrix values (PMV) for a commercially available PFA, and we assessed nutrient sparing when the product was combined with a commercial phytase, carbohydrase, and protease that can be described as an exogenous enzyme blend (EEB). In experiment 2, we determined the TMEn and true amino acid digestibility (TAAD) of the diets used in experiment 1. Main effects and interactions of PFA, PMV, and EEB were determined. Decreasing the basal diet by the PMV of the PFA decreased broiler BW gain and increased FCR. Including PFA in this diet restored BW gain and FCR. The PFA was not additive or synergistic with EEB. Incorporating PFA with PMV and EEB tended to decrease the TMEn and tested the TAAD. Decreased 4- to 21-d broiler BW gain, TMEn, and TAAD associated with using PFA with PMV and EEB may be associated with several mechanisms regarding plane of nutrition, gut microflora, substrate competition, or their combination.

Corn types with different nutritional profiles, extruded or not, on piglets (6 to 15 kg) feeding

Two experiments were carried out to determine the nutritional value and verify piglets' performance in the nursery phase fed with diets containing common corn (CC), extruded common corn (ECC), high-lysine corn (HLC), extruded high-lysine corn (EHLC), high-oil corn (HOC) and extruded high-oil corn (EHOC). In the total digestibility trial 14 barrows averaging 6.49 ± 0.16 kg initial body weight were allotted in metabolism cages, distributed in a randomized design with seven diets, six replicates, and one piglet per experimental unit. The values of digestible energy (DE), as well as metabolizable energy (ME) as-fed basis for CC, ECC, HLC, EHLC, HOC and EHOC were: 3,428 and 3,327 kcal/kg; 3,439 and 3,355 kcal/kg; 3,533 and 3,414 kcal/kg; 3,515 and 3,427 kcal/kg; 3,483 and 3,377 kcal/kg; 3,585 and 3,482 kcal/kg, respectively. In the performance experiment, 84 piglets, weaned at 21 days old, initial live weight of 6.06 ± 0.54 kg were used. Animals were allotted in a completely randomized design in a 3 × 2 factorial arrangement, using three types of corn (CC, HLC and HOC), two forms of processing (processed or not by extrusion), seven replicates and two piglets per experimental unit. Six diets containing CC, ECC, HLC, EHLC, HOC and EHOC were studied. There were no advantages in the digestibility and performance by extruding the types of corn with different nutritional profiles, for their use in commercial diets for piglets. The results of the two experiments emphasize the importance of segregating the types of corn, extruded or not, in their real chemical and energetic composition as well as the values of true digestible amino acids for the formulation of piglet diets in the nursery phase.

Prediction of the true digestible amino acid contents from the chemical composition of sorghum grain for poultry

Accurate knowledge of true digestible amino acid (TDAA) contents of feedstuffs is necessary to accurately formulate poultry diets for profitable production. Several experimental approaches that are highly expensive and time consuming have been used to determine available amino acids. Prediction of the nutritive value of a feed ingredient from its chemical composition via regression methodology has been attempted for many years. The artificial neural network (ANN) model is a powerful method that may describe the relationship between digestible amino acid contents and chemical composition. Therefore, multiple linear regressions (MLR) and ANN models were developed for predicting the TDAA contents of sorghum grain based on chemical composition. A precision-fed assay trial using cecectomized roosters was performed to determine the TDAA contents in 48 sorghum samples from 12 sorghum varieties differing in chemical composition. The input variables for both MLR and ANN models were CP, ash, crude fiber, ether extract, and total phenols whereas the output variable was each individual TDAA for every sample. The results of this study revealed that it is possible to satisfactorily estimate the TDAA of sorghum grain through its chemical composition. The chemical composition of sorghum grain seems to highly influence the TDAA contents when considering components such as CP, crude fiber, ether extract, ash and total phenols. It is also possible to estimate the TDAA contents through multiple regression equations with reasonable accuracy depending on composition. However, a more satisfactory prediction may be achieved via ANN for all amino acids. The R(2) values for the ANN model corresponding to testing and training parameters showed a higher accuracy of prediction than equations established by the MLR method. In addition, the current data confirmed that chemical composition, often considered in total amino acid prediction, could be also a useful predictor of true digestible values of selected amino acids for poultry.

Digestibilidade dos aminoácidos do milho, farelo de soja e gérmen integral de milho em galos e frangos de corte cecectomizados

Este experimento foi conduzido para avaliar a digestibilidade dos aminoácidos do milho, farelo de soja e gérmen integral de milho em galos e frangos de corte cecectomizados. Foram utilizados 16 galos Lohmann-LSL com 45 semanas de idade, 40 frangos de corte machos AgRoss 508, sendo 20 com 21 dias de idade e outros 20 com 42 dias de idade, todos cecectomizados. Adotou-se delineamento inteiramente casualizado com três categorias animais (galos; frangos aos 21 dias; e frangos aos 42 dias de idade) para cada alimento avaliado e cada ave considerada uma unidade experimental. O ensaio durou 84 horas: nas 36 horas iniciais, as aves foram submetidas a jejum e nas 48 horas subsequentes, à ingestão forçada dos alimentos, feita com sonda esofágica introduzida diretamente no inglúvio das aves. As excretas produzidas foram colhidas duas vezes ao dia nas 48 horas subseqüentes. Os valores de aminoácidos digestíveis verdadeiros determinados para o milho e gérmen integral de milho determinados com frangos submetidos ao procedimento experimental aos 21 dias de idade foram inferiores aos do grupo controle (galos). Contudo, os mesmos resultados não foram observados para o farelo de soja. O aproveitamento de aminoácidos foi maior nos frangos submetidos ao procedimento experimental aos 42 dias de idade em comparação aos do grupo controle (galos adultos), independentemente do alimento avaliado. O teor de aminoácidos digestíveis verdadeiros totais obtidos foi de 7,24; 6,25 e 7,33% para o milho, 9,66; 9,14 e 9,91% para o gérmen integral de milho e 41,82; 41,78 e 42,02% para o farelo de soja, valores determinados com galos, frangos aos 21 e aos 42 dias de idade, respectivamente. Observou-se que, com o amadurecimento do trato digestório, aumenta o aproveitamento proteico em aves que consomem milho e gérmen integral de milho.

Digestibility for dogs and cats of meat and bone meal processed at two different temperature and pressure levels*

This study evaluated the effect of two rendering processes applied to meat and bone meal (MBM) production, associated or not with extrusion, by measuring diet apparent total tract digestibility of dogs and cats, and true digestibility of amino acids (AA) by cecectomized roosters. Four diets were evaluated, with the main protein source as follows: conventional and extruded MBM; high temperature and pressure (HPT; 135 °C, 3 bar, 20 min) and extruded MBM; conventional non-extruded MBM; HPT non-extruded MBM. Nutrient digestibility and food metabolizable energy content were evaluated with dogs and cats by the method of total collection of faeces. True AA digestibility was evaluated by a precision-fed assay with cecectomized roosters. The evaluated MBM had high-ash content. The HPT process of MBM increased the digestibility of crude protein of the diets by cats, and the true digestibility of several AA by cecectomized roosters. The extrusion process did not modify the apparent total tract nutrient digestibility of MBM by dogs and their amino acid digestibility by roosters, but increased the digestibility of the dietary protein by cats. Dogs fed HPT MBM presented a higher urea post-prandial response, suggesting reductions in bioavailability and protein synthesis from absorbed AA.

Corns with Different Nutritional Profiles on Growing and Finishing Pigs Feeding (30 to 90 kg)

Three experiments were carried out to determine the nutritional value and to verify the pig performance in growing and finishing phases (30 to 90 kg) fed on diets containing common corn (CC), high-lysine corn (HLC) and high-oil corn (HOC). In the total digestibility trial (Exp. I) 12 barrows were used. Values of digestible energy (DE) and metabolizable energy (ME) as-fed basis for CC, HLC and HOC, were: 3,396 and 3,275 kcal/kg; 3,248 and 3,139 kcal/kg; 3,445 and 3,308 kcal/kg, respectively. In order to determine the apparent and true ileal digestibility coefficients of amino acids, as well as the values of true digestible amino acids of the CC, HLC and HOC, an ileal digestibility trial was done (Exp. II) with T-cannulated barrows (T simple). The treatments consisted of three diets, with one of them as the sole source of protein (CC, HLC and HOC). In the performance experiment (Exp. III), 36 crossbred pigs, allotted in a completely randomized design with three treatments and 12 replications were used. Treatments consisted of three diets: 1 - CC; 2 - HLC and 3 - HOC. It was observed no difference for performance and carcass variables among the corns with different nutritional profiles. Results of the three experiments highlighted the importance of segregating corns in their real chemical and energetic composition as well

True and apparent digestibility of protein and amino acids of feed in Nile tilapia

It was determined in this work the coefficients of apparent and true digestibility of protein and amino acids of five feeds (corn, wheat bran, soybean meal, corn gluten meal, fish meal) in Nile tilapia. It was used 252 reverted Thai strain Nile tilapia (Oreochromis niloticus) in growth phase, with weight of 310 ± 9.68 g, distributed in experimental randomized blocks design, with five treatments, six replicates per treatment and seven fish per experimental unit. Each experimental diet contained a single source of protein, composed by the studied ingredients. An additional group of fish was fed protein-free diet for quantification of the endogenous fraction and determination of true digestibility coefficients. Digestibility was estimated by the indirect method by using chromium oxide at the concentration of 0.50% of the diet as a marker, performing fecal collection at every four hour interval by using decantation technique. Coefficients of apparent digestibility of the protein and amino acids are: corn, 83.57 and 82.45%; wheat bran 82.87 and 81.47%; soybean meal 91.12 and 89.41%; corn gluten meal 90.07 and 87.78%; fish meal 83.53 and 81.65% respectively. Coefficients of true digestibility of protein and the mean of the amino acids are: corn, 90.02 and 89.60%; wheat bran 89.62 and 89.14%; soybean meal 93.58 and 91.88%; corn gluten meal 92.50 and 90.34%; fish meal 86.01 and 84.27%, respectively.

The effects of supplementary bacterial phytase on dietary true metabolisable energy, nutrient digestibility and endogenous losses in precision fed turkeys

1. A total of 40 female BUT9 turkeys were used in a precision-feeding assay to investigate the effect of dietary phytase on true metabolisable energy corrected for N retention (TME N ), coefficients of true dry matter (TDMD), mineral, amino acid and nitrogen (TND) digestibilities and the excretion of endogenous mucin, measured as sialic acid (SA). 2. Five treatments were used in this study: control (C), C + 250 phytase units (FTU) per kg feed, C + 500 FTU, C + 2500 FTU, and glucose only for endogenous losses estimation. Diets were formulated to be nutritionally adequate with the exception that the P content was relatively low (3·6 g/kg non-phytate P). 3. Inclusion of phytase increased TND in a quadratic manner with the optimum being achieved at approximately 500 FTU, at which TND was 37 % greater than in the control. The concentration of SA in the excreta decreased linearly with increased phytase supplementation. Dietary TME N , TDMD and true mineral digestibility coefficients were not significantly affected by phytase supplementation. 4. Phytase inclusion increased digestibility coefficients for indispensable, dispensable and total amino acids in a linear manner. The scale of the response to phytase was greatest with threonine and least with lysine digestibility, suggesting a specific mechanism of action that benefits gut health. 5. The strong negative relationship between secretion of SA and threonine digestibility suggests that a large part of the threonine benefit may be from reduced mucin synthesis. This supports the hypothesis that dietary phytase may play a role in improving the health status of the intestine and, as a result, reduces the maintenance energy requirements of turkeys.

Evaluation of protein and energy quality of poultry by-product meal using poultry assays

In the present study, two experiment were conducted to evaluate three poultry by-product meal (PBM; A, B and C), that is produced in commercial rendering plants. In first experiment, true amino acids (AA) digestibility and TMEn of the PBM were determined using the precision-fed cecectomized rooster. In second experiment, 1 week old male chicks were fed from 8 to 21 days of age with a corn-SBM diet or diets containing 5 or 10% PBM C formulated to be equal in total or digestible AA to the corn-SBM diet. TMEn and true amino acid digestibility varied among PBM (P 0.05) than that of the chicks fed the corn-SBM diet. The results of this study indicated that PBM has substantial nutritional value for poultry and diets containing 10% PBM in chick diets had no detrimental effects on performance if the diets were formulated to contain adequate levels of digestible AA. Key words: Energy, protein quality, poultry by-product meal.

Composição química, valores energéticos e digestibilidade verdadeira dos aminoácidos de farinhas de carne e ossos e de peixe para aves

Foram determinados a composição química, os valores energéticos, os coeficientes de digestibilidade e aminoácidos digestíveis verdadeiros de subprodutos de abatedouros, pelo método da "alimentação forçada" com galos cecectomizados. O delineamento experimental utilizado foi o inteiramente casualizado, com duas farinhas de peixe (FP1 e FP2), duas farinhas de carne e ossos (FCO1 e FCO2) e uma dieta jejum, tendo seis repetições e um galo por unidade experimental. Os valores de energia metabolizável aparente (EMA), EMA corrigida pelo balanço de nitrogênio (EMAn), energia metabolizável verdadeira (EMV) e EMV corrigida pelo balanço de nitrogênio (EMVn), valores expressos em kcal/kg de matéria natural, foram de 3.060, 3.188, 2.347 e 2.191 para a FP1, 3.238, 3.181, 2.603 e 2.377 para a FP2, 3.932, 4.057, 3.182 e 3.026 para a FCO1 e de 3.399, 3.710, 2.587 e 2.501 para a FCO2. Os coeficientes de metabolizabilidade da EMA, EMAn, EMV e EMVn, em porcentagem da energia bruta (EB), foram de 61,42; 64,99; 78,94 e 68,23 para a FP1, 63,58; 63,45; 80,94 e 74,00 para a FP2, 52,67; 58,40; 71,40 e 58,05 para a FCO1 e 49,04; 53,20; 67,73 e 55,97 para a FCO2. Os coeficientes médios de digestibilidade verdadeira dos aminoácidos essenciais e não-essenciais, em porcentagem, para a FP1, FP2, FCO1 e FCO2 foram, respectivamente, 94,32 e 92,87; 92,95 e 90,47; 83,24 e 76,94 e 83,83 e 76,96.

True Amino Acid Digestibility of Fermented Shrimp Waste in Broiler Chicks

Thirty 55 days old of MB-202 male broiler chicken were used in a completely randomized design to evaluate the digestibility of Aspergillus sp. fermented shrimp waste (FSW) by force feeding technique. There were 4 dietary treatments, each having 6 replicates. Three diets each of A. niger FSW (FSWn) , A. oryzae FSW (FSWo) and A. sojae FSW (FSWs) were formulated and one raw SW diets as control. The birds were fasted for 24 h and force feeding as quickly as possible and total excreta sampling for amino acids digestibility evaluation. The amino acid digestibility of FSW groups were higher as compared to the raw SW. Among FSW groups treatment, the digestibilities FSWn were higher for all amino acid. Supplementation of the diets with lysine have more attention in order to utilization of FSW as broiler feedstuff.

Avaliação nutricional e energética do farelo de girassol para aves

Foram realizados dois ensaios de metabolismo a fim de determinar a energia metabolizável aparente (EMA), por meio do método de coleta total de excretas com frangos, e a energia metabolizável verdadeira (EMV) e a digestibilidade verdadeira dos aminoácidos do farelo de girassol, por meio do método de alimentação forçada com galos cecectomizados. No primeiro ensaio, foi utilizado o delineamento experimental inteiramente ao acaso com 80 frangos Cobb, distribuídos em dois tratamentos, ração referência (RR) e RR mais 20% de inclusão de farelo de girassol e oito repetições e cinco aves por unidade experimental. No segundo ensaio, foi utilizado o delineamento experimental inteiramente ao acaso com 14 galos Leghorn, distribuídos em dois tratamentos, farelo de girassol e jejum, sete repetições e um galo por unidade experimental. O farelo de girassol apresentou 90,0% de matéria seca, 28,1% de proteína bruta, 4.42kcal/kg de energia bruta, 22,4% de fibra bruta, 2,9% de extrato etéreo, 0,8% de fósforo e 0,3% de cálcio. A EMV, a EMV corrigida, a EMA e a EMA corrigida determinadas foram 3.013; 2.200; 2.141 e 1.983kcal/kg, respectivamente. A lisina foi o aminoácido essencial que apresentou a menor digestibilidade e a arginina, a maior.

Effects of Dietary Fat Levels on Amino Acid Digestibility at Different Sites of Chicken Intestines

The present study was conducted to investigate the effects of varying dietary fat levels (3%-10%) on amino acid digestibility at different sites of fistulized chicken intestines. Chickens were fistulized to either the middle part of the jejunum (MJ), the distal end of the jejunum (DJ), the middle part of the ileum, the distal end of the ileum or the distal end of the rectum. Intestinal digesta were collected from each site of the intestine, and contents of amino acids were measured. True digestibilities of individual amino acids were not affected by the sites of intestines in the 3, 5 and 8% fat groups. The true digestibility of total amino acid in intestinal digesta at the MJ was significantly lower than that at the DJ in the 10% fat group. In addition, true digestibilities of individual amino acids at the MJ tended to be lower than those at the DJ in the 10% fat group. Comparison of the data at the MJ between groups showed that the true digestibilities of total amino acid and Met in intestinal digesta in the 10% fat group were significantly lower than those in other groups. The true digestibilities of all amino acids, except for Met, in intestinal digesta at the MJ in the 10% fat group tended to be lower than those in other groups. These results suggest that dietary fat levels influence the digestion of amino acids at the proximal part of the jejunum in chickens.

Effects of Dietary Protein Levels on Amino Acid Digestibility at Different Sites of Male Adult Chicken Intestines

The present study was conducted to investigate the effects of varying dietary protein levels on amino acid digestibility at different sites of fistulized chicken intestines. Chickens were fistulized to either the middle part of the jejunum (MJ), the distal end of the jejunum, the middle part of the ileum, the distal end of the ileum or the distal end of the rectum (DR). Intestinal digesta were collected from each site of the intestine, and contents of amino acids were measured. The true digestibilities of all amino acids in intestinal digesta at MJ were significantly lower than those at DR in the 10% protein group. In the 15% protein group, the true digestibilities of Asp, Thr, Glu, Pro, Gly, Val, Met and Ile in intestinal digesta at MJ were significantly lower than those at DR. The true digestibility of Ser in intestinal digesta at MJ was significantly lower than that at DR in the 20% protein group. In the 30% protein group, there was no significant difference in the true digestibilities of amino acids in intestinal digesta between the sites of the intestine. The true digestibilities of all amino acids in intestinal digesta at MJ in the 10% protein group were significantly lower than those in other groups. These results clearly demonstrated that dietary protein levels influence amino acid digestibility at MJ in chickens.

Improvement of pellet quality with proteins recovered from whole fish using isoelectric solubilization-precipitation

Muscle proteins are known to form thermally induced gel networks and may bind particles such as feed constituents. Dietary incorporation of functional proteins may improve pellet quality. Muscle proteins were recovered from rainbow trout by using isoelectric solubilization-precipitation. The objectives of this study were 1) to determine the proximate composition and amino acid content, AMEn, TMEn, and true amino acid digestibility of trout protein isolate and paste (TPP), and 2) to determine the effects of TPP on feed manufacturing, pellet quality, and true amino acid digestibility of broiler diets formulated to include TPP. Four treatments, consisting of 1) a control, 2) 5% TPP (HTPP), 3) 2.5% TPP (LTPP), and 4) 3.9% added moisture (MOIS), were manufactured at the West Virginia University pilot feed mill using a Latin square design. Five percent TPP had the highest pellet quality, followed by LTPP, MOIS, and the control. The improvement in pellet quality could be attributed to gelation of the recovered proteins. Addition of TPP reduced pellet mill production rate. Relative electrical energy usage decreased with MOIS but increased with HTPP relative to the control and LTPP treatments. Negative effects of increased viscosity likely associated with TPP were absent with LTPP. Digestibility of Asp, Glu, Pro, Ile, and Leu were lower for HTPP than the control. However, Ala digestibility was decreased in LTPP compared with the control. Therefore, fish muscle proteins incorporated at less than 5% of the diet may be beneficial to the broiler industry as a pellet binder and nutritive feed additive.

Estimation of true intestinal digestibility of dry matter, nitrogen and amino acids of cowpea and silverleaf desmodium forage legumes and Brachystegia spiciformis (musasa) browse legume

True intestinal digestibility of dry matter (DM), rumen-undegraded dietary protein (UDP) and amino acids of cowpea, silverleaf desmodium and Brachystegia spiciformis (musasa) were estimated. The true intestinal digestibility was calculated as the difference between the content of a bag that was preincubated in the rumen for 12, 24 and 48 h and was recovered in the faeces. Significantly higher DM and nitrogen disappearance rate in the rumen, postruminally and throughout the whole tract were found for cowpea than for silverleaf desmodium and musasa. Total amino acids or true nitrogen digestibility values of silverleaf desmodium and musasa tended to be higher than in cowpea. The true digestibilities for the individual amino acids in the different undegraded protein sources showed significant differences. The true intestinal digestibility of DM, nitrogen and amino acids in the mobile bags after 24 h and 48 h of preincubation in the rumen were higher for silverleaf desmodium and musasa, than in cowpea. Musasa and silverleaf desmodium provided little rumen-degradable nitrogen and supplied UDP to the intestines. The UDP supplied postruminally would be used for productive processes such as milk production and growth.

Apparent and true amino acid digestibility of artemia meal in broiler chicks (Short communication)

In order to determine the amino acid digestibility of artemia meal, five-week old male broiler chicks were given a semi-purified diet in which artemia meal was the sole source of protein. Apparent amino acid digestibility values of the assay diet, using ileal and excreta contents, were calculated using chromic oxide as indigestible marker. True digestibility values were calculated using endogenous output determined by feeding a nitrogen-free diet. The results showed that in determination of apparent amino acid digestibility of excreta, serine had the lowest (0.80) and methionine the highest (0.92) digestibility, while glycine had the lowest (0.88) and arginine and leucine the highest (0.95) apparent ileal digestibility. In measuring true excreta and ileal amino acid digestibility, alanine and glycine had the lowest (0.90 and 0.93) and methionine the highest (0.96 and 0.99) digestibility, respectively. In general, the site of measurement had no effect on apparent or true amino acid digestibility of artemia meal.

Coeficiente de digestibilidade verdadeira dos aminoácidos e valores de aminoácidos digestíveis do milho submetido a diferentes temperaturas de secagem e períodos de armazenamento

Determinou-se o coeficiente de digestibilidade verdadeira dos aminoácidos de amostras de milho submetidas a diferentes temperaturas de secagem (temperatura ambiente e secagem artificial a 80, 100 e 120°C) e períodos de armazenamento (0, 60, 120 e 180 dias). A digestibilidade verdadeira dos aminoácidos foi determinada pelo método de "alimentação forçada" utilizando-se galos Leghorn adultos cecectomizados, alojados individualmente em baterias metálicas. Utilizou-se delineamento inteiramente casualizado em esquema fatorial 4 × 4 (quatro temperaturas de secagem e quatro períodos de armazenamento) com um galo por unidade experimental e oito repetições por temperatura de secagem e período de armazenamento. As perdas endógenas foram determinadas com galos em jejum. O aumento da temperatura de secagem ocasionou redução linear da digestibilidade de metionina + cistina e isoleucina e efeito quadrático sobre a digestibilidade de metionina, treonina, lisina, triptofano e fenilalanina. Os maiores coeficientes de digestibilidade de metionina, treonina, lisina, triptofano e fenilalanina foram observados nas temperaturas 40, 25, 27, 32 e 40°C, respectivamente, obtidas por equação de regressão. Observou-se redução linear da digestibilidade de metionina e treonina com o tempo de armazenamento. A temperatura de secagem e o tempo de armazenamento dos grãos de milho reduzem a digestibilidade da maioria dos aminoácidos.