David D. Maenz

The effect of minerals and mineral chelators on the formation of phytase-resistant and phytase-susceptible forms of phytic acid in solution and in a slurry of canola meal

Abstract Minerals can readily bind to phytic acid and thus have the potential to form mineral–phytate complexes that may be resistant to hydrolysis by phytase activity of animal, plant and microbial origin. In simple solution, at pH 7.0, mineral concentrations from 0.053mM for Zn 2+ up to 4.87mM for Mg 2+ caused a 50% inhibition of phytate-P hydrolysis by microbial phytase. The rank order of mineral potency as inhibitors of phytate hydrolysis was Zn 2+ ⪢Fe 2+ >Mn 2+ >Fe 3+ >Ca 2+ >Mg 2+ at neutral pH. Acidification of the media to pH 4.0 decreased the inhibitory potency of all of the divalent cations tested. The inhibitory potency of Fe 3+ showed a moderate increase with declining pH. Inclusion of 25mM ethylenediamine-tetraacetic acid (EDTA) completely blocked Ca 2+ inhibition of phytate hydrolysis at pH 7. Inorganic P comprised 0.20–0.25 of the total P in a slurry of canola meal. Incubation with microbial phytase increased inorganic P up to 0.50 of total P levels. Supplementation with chelators such as EDTA, citrate and phthalate increased the efficacy of microbial phytase in hydrolyzing phytic acid. Incubation of canola meal with 100mM phthalic acid plus microbial phytase resulted in complete hydrolysis of phytate-P. Competitive chelation by compounds such as EDTA, citric acid or phthalic acid has the potential to decrease enzyme-resistant forms of phytic acid and thereby improve the efficacy of microbial phytase in hydrolyzing phytic acid.

Protein fractionation byproduct from canola meal for dairy cattle

Fiber-protein is a byproduct arising from a process for fractionating high-quality protein from canola meal. The objective of this study was to evaluate the fiber-protein fraction by examining the chemical profiles, rumen degradation, and intestinal digestive characteristics and determining the nutritive value of the fiber-protein fraction as dietary components for dairy cattle in comparison with commercial canola meal and soybean meal. Available energy values were estimated based on National Research Council guidelines, whereas total true protein content potentially absorbable in the small intestine (DVE) were predicted using the predicted DVE/degraded protein balance (OEB) model. The results show that fiber-protein was a highly fibrous material [neutral detergent fiber (NDF): 556; acid detergent fiber (ADF): 463; acid detergent lignin: 241 g/kg of dry matter (DM)] compared with canola meal (NDF: 254; ADF: 212; acid detergent lignin: 90 g/kg of DM) due to the presence of a higher level of seed hulls in fiber-protein. Compared with canola meal, fiber-protein contained 90 g/kg of DM less crude protein (CP), 25% of which consisted of undegradable acid detergent-insoluble CP. Most of the ruminally undegradable nutrient components present in canola meal appeared to be concentrated into fiber-protein during the manufacturing process and, as a result, fiber-protein showed a consistently lower effective degradability of DM, organic matter, CP, NDF, and ADF compared with both canola meal and soybean meal. Available energy content in fiber-protein contained two-thirds of that of canola meal. The DVE was one-third that of soybean meal and one-fifth that of canola meal [DVE value: 58 vs. 180 (soybean) and 291 g/kg of DM (canola meal)]. The OEB value of fiber protein was positive and about half of that of soybean and canola meal [OEB value: 74 vs. 162 (soybean) and 137 g/kg of DM (canola meal)]. Fiber-protein can be considered as a secondary source of protein in ruminant feed.

Transport of putrescine across duodenal, jejunal and ileal brush-border membrane of chicks (Gallus domesticus).

Luminal polyamines and their absorption are essential for proliferation of the enterocytes and, therefore, nutrition, health and development of the animal. The transport systems that facilitate the uptake of putrescine were characterized in chick duodenal, jejunal and ileal brush-border membrane vesicles prepared by MgCl2 precipitation from three-week-old chicks. An inwardly-directed Na+ gradient did not stimulate putrescine uptake and, therefore, putrescine transport in chick intestine. In the duodenum, jejunum and ileum, kinetics of putrescine transport fitted a model with a single affinity component plus a non-saturable component. The affinity (Kt) for [3H]putrescine transport across the brush-border membrane increased along the length of the small intestine. A model of intermediate affinity converged to the data obtained for [3H]putrescine transport with Kt approximating 1.07 and 1.05 mM or duodenum and jejunum, respectively; and high affinity with a Kt of 0.35 mM for the ileum. The polyamines cadaverine, putrescine, spermidine and spermine strongly inhibited the uptake of [3H]putrescine into chick brush-border membrane vesicles, more so for the jejunum and ileum than the duodenum. The kinetics of cadaverine, spermidine and spermine inhibition are suggestive of competitive inhibition of putrescine transport. These uptake data indicate that a single-affinity system facilitates the intestinal transport of putrescine in the chick; and the affinity of transporter for putrescine is higher in the ileum than in the proximal sections of the small intestine. In addition, this study shows that the ileum of chicks plays an important role in regulating cellular putrescine concentration.

A new assay for functional lectins: the brush border lectin agglutination assay (BBLAA)

Abstract A new method, the brush border lectin agglutination assay (BBLAA), has been developed to measure the capacity of functional lectins to agglutinate the intestinal brush border membrane. Lectins were incubated with purified chick small intestinal brush border vesicles, agglutinated membrane was isolated by low speed centrifugation and then assayed using alkaline phosphatase as a marker. The brush border agglutination activity of purified plant lectins with various carbohydrate binding specificity was compared. Tomato ( Lycopersicon esculentum ) lectin, and wheat germ ( Triticum vulgaris ) agglutinin bind N -acetyl-d-glucosamine and were found to have the highest activity. An exponential sigmoid equation fit the data obtained with wheat germ agglutinin, which is consistent with a cooperative mechanism of brush border agglutination. The N -acetyl-d-galactosamine specific lectin from soybean ( Glycine max ), and the l-fucose specific lectin from asparagus pea ( Lotus tetragonolobus ) had intermediate activity. Of the mixed carbohydrate binding isolectins from red kidney bean ( Phaseolus vulgaris ), Pha-E had intermediate activity, and Pha-L no detectable activity. Jack bean ( Canavalia ensiformus ) lectin, concanavalin A, (Con A) binds glucose/mannose residues and had marginal activity. Succinylation of con A eliminated brush border agglutination activity. The BBLAA has distinct advantages when compared to other lectin assay systems in that it measures functional agglutination activity directed toward the target membrane on the intestinal epithelium, does not require antibody or enzyme conjugation, and can be used to measure total functional lectins in extracts from diets or meals.