Digestible Amino Acid Content Research Articles

Near-Infrared Reflectance Spectroscopy in Precision Feed Formulation

Because of the problems inherent in determining the digestible amino acid content of batches of feedstuffs used for the formulation of feeds, feed manufactures routinely over-formulate for digestible amino acids. A producer wishing to assure that no more than 20% of the batches of feed produced are nutritionally inadequate must over-formulate by 7.5% for a feed containing 65% maize, 25% soybean meal, and 5% poultry by-products when using randomly-selected batches of these feedstuffs. Selecting batches based on protein content allows for a reduction of this safety margin to 6.3%, since protein is a predictor, albeit a poor one, for digestible amino acid content.Near-Infrared Reflectance Spectroscopy (NIRS) was evaluated as a tool to directly predict the digestible amino acid content of animal meals with the objective to develop a nutritionally relevant quality control tool. Using a database containing 78 animal meals, we developed calibrations that explained 70-90% of the variation in digestible amino acid content. Achieving such a degree of accuracy for all feedstuffs of interest would permit over-formulation to be reduced to 3%. The precision of NIRS technology and its short sample analysis time would give feed mills an efficient, economical quality control tool for producing feeds that more accurately match the nutritional profile calculated.

Nutrient Composition of Spent Hen Meals Produced by Rendering

To obtain information on the nutrient content and variability of spent hen meal, we examined meal produced form end-of-lay hens by three Renderers using conventional rendering procedures. Meal from three Renderers varied considerably in nutrient content. Amino acid content as percentage of sample varied among Renderers, but when expressed as percentage of protein less variability was observed, especially for amino acids of practical concern. Although amino acid digestibility varied somewhat among sources, overall agreement was good; values in the present study should provide guidelines for estimating digestible amino acid content of spent hen meals produced by conventional rendering. Mean amino acid digestibility among sources was not directly associated with digestibility in 0.2 or 0.002% pepsin. Nutrient content of samples produced by a commercial renderer over a 27-wk period appeared reasonably consistent

Diet Formulation for Broilers Based on Total Versus Digestible Amino Acids

A number of true amino acid digestibility assays were conducted in adult roosters on a range of feedstuffs. Using these feedstuff batches, different broiler starters and growers were formulated. A corn-soy positive control diet with high amino acid digestibility (HD) was compared to another diet using various by-products to partially replace corn and soybean meal. This second diet with low amino acid digestibility (LD) was formulated to contain the same levels of total lysine and total sulfur amino acids as diet HD. A third diet (LD + AA) was similar to diet LD, but with L-lysine•HCl and DL-methionine added to obtain levels of true digestible amino acids equal to diet HD. All three treatments consisted of a starter diet fed to 21 days and a grower diet fed to 42 days of age. Diet LD significantly depressed growth, feed efficiency, and breast meat yield compared to control diet HD. Balancing digestible amino acid contents by additional L-lysine•HC1 and DL-methionine essentially restored growth performance and carcass quality to the level of the control diet. This result demonstrates the potential benefit of switching diet formulation from total to digestible amino acids. The analysis of feed cost per kg broiler weight or per kg breast weight revealed considerable benefits from cheap by-products when diets were properly balanced in their digestible amino acid contents.

True ileal digestibility of amino acids in meat and bone meal for the growing pig—application of a routine rat digestibility assay

Eight samples of meat and bone meal were evaluated for their nutrient compositions and true digestible amino acid contents using a routine rat ileal digestibility assay. The rat assay has been validated for application to the growing pig. Ileal endogenous amino acid excretion, used for the correction of apparent digestibility values to true estimates, was determined for rats given a protein-free diet, or an enzymically hydrolysed casein (EHC) based diet and after ultrafiltration of the ileal digesta. The meat and bone meals varied in their nutrient composition and in the true ileal digestibility of protein and amino acids. The gross contents (g per 100 g air-dry weight) for crude protein, ash, lysine and methionine + cystine ranged from 47.8 to 59.3, 19.1–31.1, 2.45–3.89 and 1.25–1.93, respectively. Mean ileal endogenous nitrogen (N) and amino acid flows were significantly higher with the EHC versus the protein-free method, except for histidine and glycine. The mean ileal endogenous N flows were 1843 μg and 1124 μg g −1 food dry matter intake for rats fed the EHC and protein-free diets, respectively. The true nitrogen and amino acid digestibility coefficients based on endogenous flows determined by the EHC method were markedly higher than those determined using the traditional protein-free method. The true ileal N and lysine digestibility coefficients based on the respective endogenous flows for rats fed the EHC diet ranged from 62.7 to 88.9% and 66.4–92.3%, respectively. Values determined with endogenous flows for rats fed the protein-free diet ranged from 59.0 to 85.2% for N, and 63.2–88.9% for lysine. The variable ileal digestible N and amino acid contents of meat and bone meal emphasise the limitation of tabulated compositional values and the need for a routine relatively inexpensive digestibility assay.

Apparent ileal digestibility of crystalline l-tryptophan in young pig diets

An Increasing amount of data are being generated on the digestible amino acid content of feedstuffs. Progress towards formulations based on digestible amino acids rather than total values is promising. A wider variety of feedstuffs may feature in feed formulations along with greater use of crystalline amino acids when more confidence can be placed on their digestible amino acid values. However crystalline amino acids are often assumed to be 100 per cent digestible. This study was designed to assess the digestible value of crystalline L-tryptophan in young pig diets.

The ileal digestibility of nitrogen and amino acids in meat and bone meals determined using a rat assay

The proximate and gross amino acid compositions of meat and bone meals from three rendering plants sampled five times throughout the killing season and from one plant sampled on four occasions, were determined. Apparent and true ileal nitrogen and amino acid digestibilities were determined using a rat assay on three of the samples from each plant. There was considerable between- and within-plant variation for most of the chemical components, in particular the amino acids. Mean apparent ileal nitrogen digestibility of the 12 samples was 0.64 with a range of 0.54–0.75. Ileal apparent amino acid digestibilities of the meals, with a few exceptions, showed a similar pattern to nitrogen digestibility. Regression equations derived for the prediction of apparent ileal amino acid digestibilities from apparent ileal nitrogen digestibility had residual standard errors of 0.04–0.10. Endogenous ileal nitrogen and amino acid excretions were determined following protein-free alimentation. The resultant overall mean differences between true and apparent ileal amino acid digestibility ranged from 0.019 (arginine) to 0.094 (threonine) and that for nitrogen digestibility was 0.046. The variable ileal digestible amino acid content of meat and bone meals emphasises the limitation of tabulated analytical values and the need for a routine relatively inexpensive assay if the meals are to be used efficiently as protein supplements in diet formulation.

Factors affecting the requirement of dietary sulphur-containing amino acids of young pigs.

In the first of 3 experiments, requirement for total and digestible sulphur amino acids (SAA) was estimated in 240 pigs, 14 to 40 kg. A diet with low digestible amino acids content (digestible sulphur amino acids (SAA) 0.37%) was supplemented with all essential amino acids except methionine and 0, 0.05, 0.1, 0.1 or 0.2% synthetic DL-methionine added, providing diets with 0.42, 0.47, 0.52 and 0.57% digestible SAA. A control diet contained 0.52% digestible SAA. At similar levels of digestible SAA, there was no difference in performance between the experimental and the control diet, showing that optimum performance can be obtained with a less digestible diet supplemented with essential amino acids. Optimum performance was at 0.52% digestible SAA content in the diet, corresponding to about 0.65% total SAA. In experiment 2, 360 pigs 15 to 40 kg, were used to study SAA requirement at sub-optimal (0.60%) and optimal (0.70%) dietary threonine levels. Increasing threonine from 0.60 to 0.70%, increased (P