The rate of chromium transit through the gastrointestinal tract

The effect of drying method temperature, collection method, and marker type on apparent ileal amino acid digestibility in 21-day-old broilers fed corn-soybean meal-barley based diet

For accurate estimation of nutrient digestibility, an ideal drying and sampling method is required to preserve the quality of the digesta. A standard corn-soybean meal (corn-SBM) broiler starter diet was fed from d 0 to 10 before birds were placed on the experimental diets until d 21. One hundred and sixty-eight male Cobb 500 broiler chicks were used to evaluate the effect of two drying methods (freeze-dryer vs. forced air-oven) and two drying temperatures (40 vs. 55°C) (Exp 1), while ninety-six chicks were used to evaluate the effect of flushing and squeezing as well as marker types (titanium vs. chromium) on apparent ileal DM, N, Ca, P, and AA digestibility (Exp 2). There were seven (Exp 1) or eight (Exp 2) replicate cages per treatment with 6 birds/cage. Digesta from the distal two thirds of the ileum was obtained from birds following euthanasia on d 21 by squeezing (Exp 1) and squeezing or flushing (Exp 2). Samples collected were stored in the freezer at -20°C until they were either freeze-dried (FD) or oven-dried (OD) at 40 or 55°C. There were no interactions between the drying methods and drying temperatures (Exp 1) on apparent ileal DM, N, and AA digestibility. Met had the highest (92.3%) while Cys had the lowest (73.8%) digestibility value. In Exp 2, no interaction between sampling methods and marker types was observed. The effect of sampling methods was not significant except for Arg and Met where squeezing resulted in higher (P < 0.05) digestibility values. Furthermore, apparent ileal His, Ile, Cys, Ser, and Tyr digestibility tended to be higher (P < 0.1) in squeezed digesta compared to the flushed digesta. Results from these studies showed that OD ileal digesta at 40 or 55°C had no negative effect on apparent ileal AA digestibility. Likewise, marker type did not influence apparent ileal AA digestibility values.

Chromium chloride increases insulin-stimulated glucose uptake in the perfused rat hindlimb

AIM

To determine the effect of chromium chloride (CrCl3 ) on healthy skeletal muscle glucose uptake in the absence and presence of submaximal insulin using the rat hindlimb perfusion technique.

METHODS

Sprague-Dawley rats were randomly assigned to an experimental group: basal (Bas), chromium chloride (Cr), submaximal insulin (sIns) or chromium chloride plus submaximal insulin (Cr-sIns).

RESULTS

Insulin significantly increased [H(3)]-2 deoxyglucose (2-DG) uptake in the gastrocnemius muscles. Additionally, Cr-sIns displayed greater rates of 2-DG uptake than sIns (Cr-sIns 6.86 ± 0.74 μmol g h(-1) vs. sIns 4.83 ± 0.42 μmol g h(-1)). There was no difference between Cr and Bas treatment groups. It has been speculated that chromium works to increase glucose uptake by increasing insulin signalling. We found that Akt and AS160 phosphorylation was increased in the sINS treatment group, while chromium treatment had no additional effect on Akt or AS160 phosphorylation in the absence or presence of insulin. Cr-sIns significantly increased plasma membrane GLUT4 concentration above that of sIns (Cr-sIns 72.22 ± 12.7%, sIns 53.4 ± 6.1%), but in the absence of insulin, chromium had no effect.

CONCLUSION

Exposure of healthy skeletal muscle to chromium may increase skeletal muscle insulin-stimulated GLUT4 translocation and glucose uptake. However, these effects do not appear to result from enhanced insulin signalling proximal to AS160.

Amino acid digestibility and metabolizable energy of genetically selected soybean products

To determine the ME and amino acid digestibility of 5 soybean meal (SBM) samples, a precision-fed rooster assay and a chick assay were conducted. The 5 samples were cold-pressed (extruded) soybean meals or solvent-extracted (defatted) soybean meal. Of the cold-pressed varieties (unheated), there was an ultra-low trypsin SBM, a low-trypsin SBM, and a heated and unheated commodity SBM. The solvent-extracted SBM was a heated commodity blend. The TME and AME values were compared between each category: cold-pressed and defatted, as well as between the 2 assays. Semipurified diets containing dextrose as the main energy source were formulated to meet the bird's nutrient requirements, with each diet containing a different SBM product. The TME rooster assay was a precision-fed rooster assay in which 5 birds per diet were fasted for 24 h, crop intubated with 35 g of the test diet containing 46.58% cold-pressed or defatted SBM, and excreta was then collected for 48 h. The total aromatic amino acids rooster assay followed the same protocol, but cecectomized birds were used. For the chick assay, 480 one-day-old chicks were fed a standard corn-SBM starter diet until 17 d of age, and on d 18, the chicks were allowed ad libitum access to the SB-dextrose diets. Excreta were collected on d 22, dried, ground, and analyzed for gross energy and CP to determine ME. The SBM samples that were genetically selected to have lower trypsin inhibitor levels and higher protein had higher ME values and increased amino acid digestibility than the commodity cold-pressed SBM samples. Genetic selection of soybeans for certain traits can have positive effects on the ME value and amino acid digestibility for roosters and chicks.

Factors affecting endogenous amino acid flow in chickens and the need for consistency in methodology

Accurate estimation of ileal endogenous amino acid (EAA) losses is important when formulating diets on a standardized ileal digestible amino acid basis. In addition to the undigested and unabsorbed amino acids of dietary origin, amino acids of endogenous origin, which can be basal or diet specific, are found in digesta. The improvement in the techniques used in amino acid analysis as well as a shift from sampling excreta to ileal digesta has resulted in more accurate amino acid digestibility coefficients. Despite this, however, it is important to determine the amino acids in the digesta that are of endogenous origin. Although the need for standardization and its associated advantages is still subject to debate, it is important to evaluate how values from various methodologies compare. Several methods have been used to estimate ileal EAA flow. The classical methods, including the regression method, the use of nitrogen-free diet (NFD), and the fasted cecectomized rooster method, are the most widely used. The criticisms with the last 2 methods are that birds are not in a normal physiological state and the ileal EAA flow is, therefore, underestimated. Different methods have resulted in different endogenous flow estimates, with the NFD method having the lowest values when compared with flows from the regression and highly digestible protein methods. In addition to the influence of methods on ileal EAA flows, the influence of the age of the birds on flow is important. Data on EAA losses are copious in the literature; however, variation in data across and within laboratories calls for investigation of factors contributing to the variation. This review compares results from different methods and examines the issue of repeatability and consistency of EAA losses data from different laboratories. Finally, composition of an NFD for estimating EAA losses is proposed.

A comparison of methods to determine amino acid digestibility of feed ingredients for chickens

Two experiments were conducted to compare standardized ileal amino acid (AA) digestibility in 7- and 21-d-old chicks and true AA digestibility as determined by the precision-fed cecectomized rooster assay for several ingredients used in poultry feeds. Diets were formulated to contain soybean meal, cottonseed meal, poultry by-product meal, and fish meal in experiment 1 and corn, wheat, soybean meal, poultry by-product meal, feather meal, and fish meal in experiment 2 as the sole sources of protein. Celite, used as an indigestible marker, was added at 1.5% of the diet. The test diets were fed ad libitum to broiler chicks from 0 to 7 d of age in experiment 1 and from 4 to 7 and 17 to 21 d of age in experiment 2. Ileal digesta samples were collected after euthanizing the birds at 7 d of age in experiment 1 and at 7 and 21 d of age in experiment 2. Additionally, cecectomized, Single-Comb White Leghorn roosters were used for crop intubation of the test diets for determination of true AA digestibility. In experiment 1, AA digestibility of all ingredients tested was significantly lower at 7 d of age than when determined by the rooster assay. In experiment 2, no differences were detected between AA digestibility at 7 or 21 d of age in the chick assay for the majority of the indispensable AA. However, the AA digestibility coefficients obtained by the chick assay at 7 d and, in some cases, at 21 d of age, were significantly lower than those obtained by the rooster assay. In conclusion, there were differences in the AA digestibility coefficients obtained through the chick and the rooster assays. Such discrepancies could be associated with an age effect or the methodological differences between both methods.

Comparison of inert markers [chromic oxide or insoluble ash (Celite)] for determining apparent metabolizable energy of wheat- or barley-based broiler diets with or without enzymes

A broiler chick bioassay was used to measure the effect of two inert digestibility markers on the determination of dietary AME. Diets contained 80% of either wheat or barley (with or without enzyme) and either chromic oxide at 0.5% or one of three levels of insoluble ash (0.5, 1.0, or 1.5%) as markers. The various cereal and marker diet combinations were consumed ad libitum (0 to 21 d) by two groups of 10 male broilers in each of two trials. The AME of each diet was determined by measuring the respective marker ratios between diet and excreta (collected for 24 h at 7 or 21 d) or ileal digesta collected at 21 d. Growth and feed conversion were measured on each group of birds between 0 and 21 d. There was no effect of marker on growth or feed efficiency. However, determination of AME of wheat- or barley-based diets with or without enzymes were affected by choice of marker and whether markers were measured in excreta (7 or 21 d) or ileal digesta. Chromic oxide was viewed as the least accurate method for determining AME, based on chronic oxide's inability to define AME differences between barley-based diets with and without enzymes, whereas insoluble ash clearly demonstrated improved AME of wheat- and barley-based diets with an enzyme. The optimum levels of insoluble ash for accuracy and repeatability were between 0.5 and 1.0%. The AME of the diets were, on average, 5% lower when determined with 7 vs 21 d excreta and 2.5% lower for ileal digesta than excreta collected at 21 d. It was concluded that identification of components that result in variability in AME levels of diets will be improved if a bioassay uses insoluble ash as a marker.

Dietary and metabolite effects on trivalent chromium retention and distribution in rats

The purpose of this study was to determine if diet or various metabolites alter chromium (Cr) uptake and distribution in rats. Radioactively labeled Cr was detected within 15 min of oral administration to rats, and the total amount retained remained relatively constant from 1 to 24 h. Dietary Cr intake did not alter Cr retention or distribution. The majority of the Cr was retained in the carcass. However, when the amount of labeled Cr was expressed per gram of tissue, the highest amounts of Cr were found in the kidneys, spleen, and pancreas. Pharmacological doses of insulin, epinephrine, glucagon, and dibutyryladenosine-3'-5'cyclic monophosphate, prostaglandins A1, A2, B1, B2, E1, E2, F1 alpha, and F2 alpha did not significantly influence Cr retention. Glucose, sucrose, nicotinic acid, glutathione, and other metabolites administered orally in conjunction with labeled Cr also did not significantly alter Cr retention. These data indicate that most nutrients and metabolites do not alter Cr retention and distribution. The regulation of Cr homeostasis appears to be at the level of excretion.

Gastrointestinal transit and digestibility of maltitol, sucrose and sorbitol in rats: a multicompartmental model and recovery study

Using data obtained with a dye marker and the gavage technique, the kinetics of gastrointestinal transit of different loads of sugar substitutes (maltitol, sorbitol) and sugar (sucrose) in the rat were analysed using a linear multicompartmental model over a range from the realistic to the non-physiologic high, of carbohydrate intake levels and using only a few experimental time points. The model gave detailed insight into intestinal propulsion and gastrocecal transit time. Rate constants of transport between the compartments investigated were determined; they showed characteristics which could be related to the substance and the dosage administered. Analyses of the gastrointestinal content and calculations of the intestinal net water movement showed that the digestibility and absorption of the disaccharide sugar alcohol, maltitol, in the small gut depended inversely on the dose ingested. For all substances tested, caloric availability in the small intestine was calculated. At a physiological low level of maltitol intake, the results also indicated an insignificant calorie-saving effect in comparison to sucrose, an effect based mainly on the slow absorption rate of the maltitol cleavage product sorbitol.