Excess excretion of nitrogen (N) caused by inaccurate animal feeding might increase the environmental concerns in terms of soil and water pollutions. Nitrogen is one of the most expensive elements in animal nutrition and either under-feeding or over-feeding of this element may be associated with financial losses through the suppressed performance or expensive diets. Determination of nutrient availability could warrant accurate feed formulation to meet animal requirements. Nutrients digestibility determination in poultry is usually carried out by collecting excreta (feces + urine) from the bird or collecting digesta from the ileum. Standardized ileum digestibility is also possible by measuring the endogenous loss of amino acids. endogenous loss of amino acids is affected by the type of protein source, the protein level of the diet, the amount of dietary fiber, the presence of anti-nutritional agents, the method of slaughter, the type of marker used, the age of the bird, the species, diet and body size. Among these factors, the level of amino acids in the diet is a major factor. Therefore, this study was conducted to determine essential amino acids digestibility of corn, wheat, soybean meal and corn gluten meal in Japanese quails during third week of age.
A total of 600 of 14-days-old Japanese quails were assigned in a completely randomized design to five treatments, four replications and 30 birds in each floor pen. The dietary treatments included nitrogen free diet, corn, wheat, soybean meal and corn gluten meal which were prepared in such a way that the test ingredient was the sole source of the protein and amino acids in each diet. The standardized ileal amino acid digestibility (SIAAD) values in aforementioned feeds were determined using direct method, and an N-free diet (NFD) was used to measure the basal endogenous amino acids losses (EAAL) from 14 to 21 d of age. Titanium dioxide was added to all diets as indigestible marker of 5 g / kg. At the end of the experiment, all the birds of each pen were killed by an intracardiac injection of 0.5 mL sodium pentobarbital. Ileal digesta were collected by gentle manipulation and pooled on a replicate basis and were immediately frozen. The ileum was considered as part of the small intestine starting from the Meckel’s diverticulum and up to 15 mm before the ileocaecal junction. Titanium was determined colorimetrically and amino acid profiles were determined for corn, soybean meal, corn gluten meal and wheat using acidic hydrolysis and chromatographically. The house temperature was set at 35, 29 and 26 ° C in the first, second and third weeks of age, respectively and the relative humidity of the house was 55-60%. The birds freely accessed water and experimental diets, and 23 h light and one h darkness was considered throughout the experiment. Data were analyzed by one-way ANOVA in Graphpad software and Tukey’s test was used to compare the means.
The EAAL values of methionine, lysine, threonine, arginine, valine, isoleucine, leucine, and histidine were determined to be 32.6, 306, 241, 104, 355, 497, 49.6, and 80.1 mg/kg DMI, respectively. The apparent digestibility values of amino acids methionine, lysine, threonine, arginine, valine, isoleucine, leucine, and histidine as a number of essential amino acids in corn were 92.97, 70.38, 79.76, 88.98, 84.75%; in wheat were 90.80, 86.47, 82.63, 86.70, 88.33, 45.79, 96.77, 81.24%; in soybean meal were 94.73, 86.96, 80.09, 14.91, 81.54, 13.85, 80.47, 95.19% and in corn gluten meal were 04.86, 84.67, 82.76, 51.89, 73.83, 18.91, 76.15, 53.67%, respectively. The SIAAD of methionine, lysine, threonine, arginine, valine, isoleucine, leucine, and histidine for corn, wheat, soybean meal, and corn gluten meal were 94.48, 83.96, 88.33, 89.80, 93.85, 92.15, 94.06, 97.53%; 92.54, 95.48, 89.81, 88.48, 94.72, 90.11, 84.17, 84.15%; 95.27, 83.08, 81.48, 91.45, 83.11, 87.82, 81.93, 95.87%; 86.27, 71.23, 87.03, 90.12, 85.11, 93.23, 76.21, and 74.38%, respectively. Research has shown that the type of ingredients and concentration of diet amino acids have a significant effect on the digestibility coefficients. This difference is in fact due to the changes in the endogenous share of amino acids in the total amount of ileal amino acids.
Generally, the highest SIAAD coefficients of methionine, lysine, and arginine were obtained in SBM and threonine was obtained in corn. On the other hand, the lowest SIAAD coefficients of these amino acids were observed in corn gluten meal, corn and wheat, respectively. Also, comparing the results of this study with findings from other species showed that the apparent and standardized ileal digestibility of essential amino acids in corn, wheat, soybean meal and corn gluten meal is different in Japanese quail than in broiler chickens.
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