Dietary whey protein influences plasma satiety-related hormones and plasma amino acids in normal-weight adult women.

BACKGROUND/OBJECTIVE: A distinct suppressive effect of a whey protein (including glycomacropeptide)-enriched preload drink on subsequent food intake in comparison with a maltodextrin carbohydrate-enriched preload was demonstrated in an earlier companion study with the same female subjects; however, the potential mediators underlying the effect are unclear. The objective of this study was to investigate how the ingestion of a whey protein-enriched preload beverage affected postprandial plasma concentrations of several satiety-related gastrointestinal hormones and metabolites in comparison with a maltodextrin carbohydrate-enriched preload. SUBJECTS/METHODS: Eighteen normal-weight women were studied in a single-blind, randomized block design. Blood samples were collected at various time intervals for 120 min after consumption of a test drink (300 ml, ~1300 kJ) enriched (45 g) with either maltodextrin carbohydrate or whey protein containing naturally present glycomacropeptide. RESULTS: Plasma-active ghrelin concentrations decreased after both maltodextrin carbohydrate- and whey protein-enriched test drinks (P<0.05). The whey protein-enriched beverage led to increased plasma concentrations of cholecystokinin (CCK) at 60 and 75 min (P<0.05), glucagon-like peptide-1 (GLP-1) at 90 min (P<0.001), peptide tyrosine-tyrosine (PYY) at 90 and 120 min (P<0.01) and pancreatic polypeptide (PP) from 15 to 120 min (P<0.05) compared with maltodextrin carbohydrate. Total amino acid, urea and ammonia plasma concentrations were also higher after whey protein compared with maltodextrin carbohydrate ingestion (P<0.01). CONCLUSIONS: Increased plasma concentrations of some gastrointestinal hormones related to satiety, particularly PP, and of amino acids and their metabolites, may have acted either singly or together to mediate the observed satiety response to whey protein.

Endogenous proteins in the ileal digesta of adult humans given casein-, enzyme-hydrolyzed casein- or crystalline amino-acid-based diets in an acute feeding study.

BACKGROUND/OBJECTIVES: To ascertain if the form of dietary nitrogen (free amino acids (AA), small peptides, or intact protein) affects the endogenous nitrogen containing substances lost from the upper digestive tract of humans. SUBJECTS/METHODS: Digesta were collected via a naso-ileal tube from the terminal ileum of 16 adult humans in a single parallel study following an acute feeding regimen. Subjects were given an iso-nitrogenous and isocaloric test meal containing 150 g of casein (CAS) (n=6), enzyme-hydrolyzed casein (HCAS) (n=5) or crystalline AA (n=5) dissolved in 550 ml of water, as the sole sources of nitrogen. RESULTS: The mean concentrations and flows of total nitrogen, protein nitrogen, and soluble protein nitrogen passing the terminal ileum were significantly higher (P <0.01) for the CAS and HCAS test-meal groups compared to the AA meal group. Dietary CAS and HCAS had a considerable influence on digesta mucin concentrations and flows compared to free AA (+41%). Only 3-4% of the total nitrogen remained unidentified. CONCLUSIONS: The form of dietary nitrogen (protein, small peptides or free AA) had an acute effect upon the secretion or reabsorption of endogenous proteins in the small intestine of healthy humans, as evident from significant differences in both the quantity and composition of the proteins found in digesta at the end of the ileum.

Recovery of intact IgG in the gastrointestinal tract of the growing rat following ingestion of an ovine serum immunoglobulin.

The aim of this study was to determine whether orally ingested ovine serum IgG partly resists digestion in the growing rat. Fifteen Sprague-Dawley male rats were allocated to one of three diets for a 3-week study: a control diet (CON) and two test diets containing either freeze-dried ovine serum immunoglobulin (FDOI) or inactivated ovine serum immunoglobulin (IOI). Samples of stomach chyme and intestinal digesta from the ad libitum-fed rats were subjected to ELISA and Western blot analysis. Amounts of intact ovine IgG for the FDOI diet were found to be 13.9, 20.0, 34.1, 13.0 and 36.9 µg in the total wet digesta from the stomach chyme, duodenal, jejunal, ileal and colonic digesta respectively. Qualitative detection by Western blot revealed the presence of intact ovine serum IgG with a ~150 kDa MW. This was detected in all of the gut segments (stomach chyme, duodenal, jejunal, ileal and colonic digesta) for growing rats fed the FDOI diet. No ovine IgG was detected in the chyme or digesta from rats fed the CON or the IOI diets. Ovine serum IgG partly resisted digestion in the growing rat fed the FDOI diet and was found throughout the digestive tract. These results provide a basis to explain the reported biological effects of orally administered immunoglobulin.

Effect of microbial phytase on phytate P degradation and apparent digestibility of total P and Ca throughout the gastrointestinal tract of the growing pig.

The effect of a dietary microbial phytase on mineral digestibility throughout the gastrointestinal tract (GIT) of the growing pig was studied. Thirty-two entire male pigs (~22 kg BW) were allocated equally to 4 corn-soybean meal diets. One diet was adequate in total P and Ca, the second diet was deficient in total P and Ca (low-P diet), and the third and fourth diets were the low-P diet with microbial phytase added at 1,107 U/kg or 2,215 U/kg, respectively. Titanium dioxide (3 g/kg) was included in the diets as an indigestible marker. The pigs were fed their respective diets for 42 d. Fecal samples were collected from d 38 to 41 and stomach chyme, terminal jejunal, and terminal ileal digesta samples were collected after euthanasia on d 42. Phytate P degradability and apparent total P and Ca digestibility were determined at the gastric, jejunal, ileal, and total tract levels. Phytate P degradation and apparent total P and Ca digestibility were not significantly different between the 2 microbial phytase inclusion levels. Across both microbial phytase-low-P diets, phytase supplementation increased (P < 0.05) phytate P degradability at the jejunal, ileal, and total tract levels by 101%, 77%, and 10%, respectively, but not at the gastric level. Total tract phytate P degradation was greater (P < 0.05) than ileal phytate P degradation for both the unsupplemented (52% units greater) and phytase-supplemented, low-P (26% units greater) diets. The latter result was not reflected by the apparent total P digestibility estimate, which was not significantly different between the ileal and total tract levels for both the unsupplemented and phytase-supplemented, low-P diets. Consequently, there appeared to be considerable phytate degradation in the hindgut, presumably due to the action of hindgut microbes, but the phytate P released in the hindgut did not appear to be absorbed. Apparent Ca digestibility was not significantly different among jejunal, ileal, and total tract levels for any of the dietary treatments, but apparent Ca digestibility was greater (P < 0.05) for the phytase-supplemented diets compared with the unsupplemented diets. Overall, dietary microbial phytase supplementation led to greater phytate degradation to the end of the jejunum. Because the phytate P released in the hindgut was not absorbed, ileal estimates, rather than total tract estimates, of phytate degradation appear to more accurately reflect P availability.

Effect of two microbial phytases on mineral availability and retention and bone mineral density in low-phosphorus diets for broilers.

1. The efficacy of supplementation of a low-phosphorus (low-P) maize-soyabean meal diet for broiler chickens with two different microbial (fungal and bacterial) phytases was examined. 2. Broiler chickens received a low-P maize-soyabean meal diet containing either no phytase or one of the two phytases included at one and two times the manufacturer's recommended inclusion level for 21 d. 3. Titanium dioxide was included in the diets as an indigestible marker. Excreta were collected quantitatively from d 18 to 21, and at the end of the study the birds were killed and ileal digesta and leg bone samples collected. 4. No differences were observed for body weight gain and feed intake or apparent metabolisable energy (AME) among all dietary treatment groups. 5. Dietary phytase supplementation improved the apparent retention of Ca, Na and Cu and ileal phytate P absorption from 32% to 44% across inclusion levels. 6. Bone mineral density (BMD) was improved for both phytases across inclusion levels by, on average, 9% for the tibia and 13% for the femur. 7. Dietary phytase supplementation of the low-P diet improved apparent ileal digestibility of serine, glycine, valine, isoleucine, tyrosine, histidine, lysine and arginine. 8. When the results from the present study were combined with the results from other similar published studies and analysed statistically, factors such as dietary P and Ca concentration, as well as bird breed and age, rather than the type or activity of microbial phytase, had the greatest impact on the extent to which dietary supplementation improved P and Ca retention. 9. More work is required to explain the interrelationships between the multiple factors influencing the efficacy of phytase on the availability of dietary minerals.

Orally administered ovine serum immunoglobulins modulate the intestinal levels of Lactobacillus and enterobacteria in the growing rat.

The aim was to determine whether orally administered ovine serum immunoglobulins modulate the gut microbiota in the growing rat. Thirty Sprague-Dawley male rats were used in a 21-d study and fed either a basal control diet (control; no immunoglobulin) or a similar diet containing freeze-dried ovine immunoglobulin (ovine Ig) with 15 individually fed rats per diet. Bacterial DNA isolated from ileal and colonic digesta were subjected to PCR-denaturing gradient gel electrophoresis (PCR-DGGE). In the ileum, the DGGE band number and diversity index were greater (P < 0.05) for rats fed the ovine Ig than those fed the control diet. The DNA sequencing of a selected DGGE band in the ovine Ig-fed rats revealed 99% similarity to the Lactobacillus strains. The quantitative PCR data revealed that supplementation of the diet with the ovine Ig fraction supported the growth of Lactobacillus and conversely decreased the number of enterobacteria in ileal and colonic digesta. Inclusion of the ovine Ig fraction led to a greater (P < 0.05) ratio for total Lactobacillus to total bacteria and total Lactobacillus to enterobacteria. The results from the present study show that dietary supplementation with ovine Ig may alter the intestinal environment by a specific enrichment of Lactobacillus strains and depletion of enterobacteria.

Gross and true ileal digestible amino acid contents of several animal body proteins and their hydrolysates.

Amino acid compositions of ovine muscle, ovine myofibrillar protein, ovine spleen, ovine liver, bovine blood plasma, bovine blood globulins and bovine serum albumin and the amino acid compositions and in vivo (laboratory rat) true ileal amino acid digestibilities of hydrolysates (sequential hydrolysis with Neutrase, Alcalase and Flavourzyme) of these protein sources were determined. True ileal amino acid digestibility differed (P<0.05) among the seven protein hydrolysates. The ovine myofibrillar protein and liver hydrolysates were the most digestible, with a mean true ileal digestibility across all amino acids of 99%. The least digestible protein hydrolysate was bovine serum albumin with a comparable mean true ileal digestibility of 93%. When the digestible amino acid contents were expressed as proportions relative to lysine, considerable differences, across the diverse protein sources, were found in the pattern of predicted absorbed amino acids.

Comparison of three markers for the determination of bacterial protein in terminal ileal digesta in the growing pig.

The aim of the study was to compare three methods commonly used to determine the concentrations of bacterial protein in digesta collected from the terminal ileum of growing pigs that had been fed a casein-based diet. The amounts of bacterial protein in terminal ileal digesta were determined using three different markers: 2.6-diaminopimelic acid (DAPA) and the d-amino acids, d-aspartic acid (d-Asp) and d-glutamic acid (d-Glu). The effectiveness of each marker was compared against a control based on physical fractionation by centrifugation. The total bacterial protein concentrations derived from the markers d-Asp and d-Glu were significantly different (p = 0.05) to those calculated from DAPA and the control, but there was no difference between DAPA and the control. The percentage of bacterial nitrogen ranged from 40% to 52% dependent on the marker used. Bacterial protein expressed as a percentage of the total protein, ranged from 48% to 62%, a substantial proportion of which (12-28%) was derived from lysed bacterial cells. Statistical correlations between the estimation methods were low. Such poor correlation between the markers may be the result of random errors such as variance in the epimerization of the two d-amino acids during protein hydrolysis. DAPA was accepted as a reliable marker for determining microbial protein in ileal digesta.

Effect of a novel phytase on growth performance, apparent metabolizable energy, and the availability of minerals and amino acids in a low-phosphorus corn-soybean meal diet for broilers.

The addition of microbial phytase to diets for broiler chickens has been shown to improve the availability of phytate P, total P, some other minerals, and amino acids. In this study, the effect of a novel microbial phytase expressed by synthetic genes in Aspergillus oryzae on amino acid and mineral availability was assessed. Phytase was incorporated (1,000 and 2,000 U/kg) into low-P corn-soybean meal-based diets for broilers. Broilers received the experimental diets for 3 wk, and excreta were collected from d 18 to 21 for the determination of AME and mineral retention. On the 22nd day, the broilers were killed and the left leg removed and ileal digesta collected. Ileal phytate P and total P absorption, ileal amino acid digestibility, as well as the bone mineral content and bone mineral density were determined. Ileal phytate P absorption and absorbed phytate P content of the low-P corn-soybean meal diet were significantly (P < 0.05) higher after dietary inclusion of the novel phytase (49-60% and 65-77% higher, respectively). Apparent ileal total P absorption and apparent total P retention was 12 to 16% and 14 to 19% higher (P < 0.05), respectively, after dietary inclusion of phytase. The bone mineral content and bone mineral density in the tibia were 32 to 35% and 19 to 21% higher (P < 0.05), respectively, after dietary phytase inclusion. The apparent ileal digestibility of threonine, tyrosine, and histidine increased significantly (P < 0.05) by 14, 9, and 7%, respectively, after dietary inclusion of microbial phytase. Overall, the inclusion of a novel microbial phytase into a low-P corn-soybean meal diet for broiler chickens greatly increased phytate P and total P absorption, bone mineral content and density, as well as the digestibility of some amino acids.

Dietary supplementation with ovine serum immunoglobulin attenuates acute effects on growth, organ weights, gut morphology and intestinal mucin production in the growing rat challenged with Salmonella enteritidis.

The aim was to determine the effect of orally administered ovine serum immunoglobulin (Ig) on growth performance, organ weight, gut morphology and mucin production in the Salmonella enteritidis--gavaged growing rat. Four groups consisted of non-gavaged rats fed a casein-based control basal diet (BD) and three groups of rats gavaged with 1×10(7) CFU S. enteritidis and fed a casein-based diet, a diet containing freeze-dried ovine Ig (FDOI) or a casein-based diet containing inactivated ovine Ig (IOI). The rats were randomly allocated to one of the four groups (n=15/group) and received their respective diets for an 18-day experimental study. Gavaging took place on day 15. Average daily gain and body gain : feed ratio (post-gavage, 3 days) were significantly (P<0.05) higher for the Salmonella-challenged rats fed the FDOI diet compared to those fed the BD and IOI diets. At the end of the study, the small intestine and colon were significantly (P<0.05) heavier for the gavaged rats fed the FDOI diet compared to the gavaged rats fed either the BD or IOI diet. Moreover, the relative weights of the caecum, liver and spleen of the gavaged rats fed the BD or IOI diet were significantly (P<0.05) heavier compared to the gavaged rats fed the FDOI diet. Generally, the gavaged rats fed the FDOI diet had significantly (P<0.05) higher goblet cell counts and luminal mucin protein contents than the gavaged rats fed either the BD or IOI diet and had a more functional gut morphology. Overall, the FDOI fraction prevented the acute effects of S. enteritidis.

Dietary supplementation with ovine serum immunoglobulin is associated with an increased gut luminal mucin concentration in the growing rat.

The mucus layer covering the gut epithelium is pivotal to host defence and is affected by various dietary components. Part of the reported beneficial effect of dietary immunoglobulins (Igs) on gut health may be due to effects on the gut mucus layer. The aim was to determine whether orally administered ovine serum Ig influence goblet cell count, mucin gene expression and digesta mucin protein content in the gut of the growing rat. Fourteen Sprague-Dawley male growing rats were used in a 21-day study and were fed either a casein-based control diet (CON; no Ig) or a similar diet but containing freeze-dried ovine Ig (FDOI). Daily food intake and growth rate were not affected by the dietary treatments. When compared to the rats consuming CON diet, those consuming the FDOI diet had significantly (P < 0.05) more intact and cavitated goblet cells in the intestinal villi. A similar result was found for crypt goblet cells in the small intestine and colon. Ileal Muc2, Muc3, Muc4 and stomach Muc5Ac mRNA expressions for the FDOI animals were higher (P < 0.05) compared to the the CON animals. Mucin protein content was higher (P < 0.05) in the stomach, ileum and colonic digesta of rats fed the FDOI diet. In conclusion, orally administered FDOI influenced gut mucins in the growing rat as evidenced by increased mucin gene expression and digesta mucin protein concentrations as well as an increased goblet cell count.

Immunomodulatory effects of ovine serum immunoglobulin in the growing rat.

This study aimed to determine whether orally administered ovine serum immunoglobulin (Ig) modulates aspects of immunity such as phagocytosis, lymphocyte proliferation, cytokine production, intestinal and plasma Ig concentrations in growing rats. Forty-five male Sprague-Dawley rats (n = 15/group) were used in the 21-day study, and fed a basal control diet (BD; no Ig) or two test diets: freeze-dried ovine Ig (FDOI) and inactivated ovine Ig (IOI). Phagocytic activity of peripheral blood leukocytes and lymphocyte proliferation in the presence of the mitogen concanavalin A (ConA) was greater (P < 0.05) for the FDOI-fed rats than for the BD- and IOI-fed groups. ConA-stimulated and unstimulated spleen cell culture produced higher (P < 0.05) interferon-γ and interleukin-4, respectively, from rats fed the FDOI than rats fed the BD diet. In the jejunum, ileum and plasma, rats fed FDOI produced higher (P < 0.05) concentrations of secretory IgA (sIgA) than rats fed IOI or BD. Rats fed the FDOI diet had greater jejunal (P = 0.037) and lower plasma (P = 0.025) rat IgG concentrations than rats fed either BD or IOI. In conclusion, an ovine Ig fraction selectively modulated various indices of immune function.

An appraisal of the strengths and weaknesses of newborn and juvenile rat models for researching gastrointestinal development.

Research on the impact of bioactive compounds on the development and functional maturation of the gastrointestinal (GI) tract using newborn and juvenile rats has greatly contributed to the knowledge of GI physiology and to the improved clinical management of both premature and full-term newborns. Of the animal models available, two types have been described for use with young rats--maintenance models and substitution models. Maintenance models are those in which the young are reared with the dam and therefore benefit from continuation of natural nutrition and maternal care. Substitution models are those in which the young are reared in the absence of the dam using artificially formulated milk delivered by various means into specific GI sites. In this review, we describe these models and their operation, and discuss the strengths and weaknesses of each. Attention is also given to questions of scientific validity and some animal welfare issues raised by the use of these models.

Effect of elevated temperature storage on the digestible reactive lysine content of unhydrolyzed- and hydrolyzed-lactose milk-based products.

The study aimed to evaluate the effects of storage at elevated temperatures on reactive Lys content and true ileal reactive Lys digestibility in a skim milk powder and a hydrolyzed-lactose skim milk powder. A validated bioassay based on guanidination of food and digesta samples was applied. Semisynthetic diets containing the milk powders as the sole sources of protein were formulated and fed to growing rats. Chromic oxide was included in each diet as an indigestible marker. Digesta were collected posteuthanasia and analyzed along with the diets for reactive Lys (homoarginine), and true ileal reactive Lys digestibility was calculated after correction for endogenous Lys loss. For the skim milk powder, there was no decrease in reactive Lys digestibility (Lys availability) when the powder was stored at 30 and 35 degrees C for 18 mo. In contrast, when stored at 40 degrees C for 12 mo, a small but statistically significant (6%) decrease was observed. For the hydrolyzed-lactose product, a 22% decrease in Lys availability was observed after storage at 35 degrees C for 18 mo, and a 17% decrease was observed when stored at 40 degrees C for only 6 mo. Digestible reactive (available) Lys content decreased by more than 20% for the skim milk powder stored at 30 and 35 degrees C for 18 mo and 40% when stored at 40 degrees C for 12 mo. Furthermore, available Lys decreased in the hydrolyzed-lactose skim milk powder by 41% when stored at 30 degrees C for only 18 mo and 34 and 65% when stored at 35 and 40 degrees C, respectively, for 6 mo. Elevated temperatures and prolonged storage periods negatively influenced the available Lys contents of both milk powders. The decrease in available Lys content and Lys availability was greater for the hydrolyzed-lactose skim milk powder compared with the normal skim milk powder, after storage at elevated temperatures.

Specific effects of gamma-linolenic, eicosapentaenoic, and docosahexaenoic ethyl esters on bone post-ovariectomy in rats.

Long chain polyunsaturated fatty acids (LCPUFAs) are involved in the regulation of bone metabolism. Increased dietary consumption of n-3, and possibly some n-6, LCPUFAs may limit postmenopausal bone loss. The aim of this study was to determine the effects on bone of specific fatty acids within the n-3 and n-6 LCPUFA families in ovariectomized (OVX) rats. Rats were OVX or sham-operated and fed either a control diet (OVX and sham) or a diet supplemented with 0.5 g/kg body weight/day of gamma-linolenic (GLA), eicosapentaenoic (EPA), docosahexaenoic (DHA) ethyl esters or a mixture of all three (MIX) for 16 weeks. Bone mineral content (BMC), area, and density and plasma concentrations of insulin-like growth factor-I, vitamin D, selected biochemical markers of bone metabolism, and parathyroid hormone (PTH) were determined. The OVX-induced decrease in lumbar spine BMC was significantly attenuated by DHA but not by EPA or GLA supplementation or supplementation with a mixture of all three LCPUFAs. Endosteal circumferences of tibiae were significantly greater in DHA and EPA compared to OVX. Plasma C-terminal telopeptide of type I collagen and osteocalcin concentrations were not significantly different in the DHA group compared to OVX. Femur BMC decreased by a significantly greater amount in GLA than OVX, and final plasma PTH concentrations were significantly higher in GLA compared to all other groups. In conclusion, DHA ameliorated OVX-induced bone mineral loss. GLA exacerbated post-OVX bone mineral loss, possibly as a result of PTH-induced bone catabolism.

The effect of a commercial enzyme preparation on apparent metabolizable energy, the true ileal amino acid digestibility, and endogenous ileal lysine losses in broiler chickens.

The effect of a commercial enzyme preparation containing xylanase, alpha-amylase, and beta-glucanase on dietary AME content and the apparent and true ileal amino acid digestibility of a corn-soy broiler diet and endogenous ileal lysine flow was determined. Two predominantly corn-soy diets also containing wheat bran and canola meal were formulated; one diet contained no added enzymes, whereas the other was supplemented with alpha-amylase, beta-glucanase, and xylanase. Titanium dioxide was included as an indigestible marker. The diets were given to broiler chickens, and AME and true ileal amino acid digestibility were determined. Portions of the 2 test diets were guanidinated and fed to similar aged broiler chickens and endogenous lysine flows determined. The chickens appeared healthy throughout the study, and the mean bird weights at the time of slaughter were not significantly different (P < 0.05) among any of the treatment groups. Dietary AME content was significantly (P < 0.05) higher for the enzyme-supplemented corn-soy diet (2,829 kcal/kg) compared with its unsupplemented control diet (2,766 kcal/kg). True ileal amino acid digestibility was significantly (P < 0.05) higher for all amino acids investigated. The increase ranged from 4% for arginine and glutamic acid to 12% for cystine. There was no significant difference in endogenous ileal lysine flow between broilers fed the unsupplemented diet and those fed the enzyme-supplemented diet. Overall, enzyme supplementation with an enzyme blend containing alpha-amylase, beta-glucanase, and xylanase increased the AME content of a corn-soy broiler diet as well as apparent and true ileal amino acid digestibility for all amino acids, but had no effect on endogenous ileal lysine flow.

Consumption of an n-3 polyunsaturated fatty acid-enriched dip modulates plasma lipid profile in subjects with diabetes type II.

OBJECTIVE: Recent developments in micro-emulsification technology have allowed the fortification of foods with long-chain n-3 polyunsaturated fatty acid (PUFA) without the undesirable fish odour/taste and with reasonable shelf life. The effects of supplementing the diets of people with diabetes type II with a hummus-based dip enriched with long-chain n-3PUFA on plasma fatty acid composition and lipid levels were examined. DESIGN: A pre- and post-intervention study. SETTING: This study was conducted at the University of Newcastle, Australia. SUBJECTS: Participants were recruited via advertisements on the University of Newcastle notice boards and in the local newspapers. Following initial response to study advertisements, information statements were mailed out to 29 potential participants. Thirteen participants were eligible and consented to participate in the trial. There were no dropouts as all the 13 participants completed 6-week intervention trial. METHODS: Free-living male and female subjects with diabetes type II (n=13) consumed the n-3PUFA-enriched dip for a period of 6 weeks. Fasting blood samples were collected pre- and post-intervention for analyses of fatty acids and plasma lipids. RESULTS: Following 6 weeks of consuming the enriched dip, all the long-chain n-3PUFA (20:5n-3, 22:5n-3 and 22:6n-3) were significantly (P<0.05) elevated in the plasma lipids. This represented an increase in 20:5n-3 content by 117%, an increase in 22:5n-3 content by 15% and an increase in 22:6n-3 content by 80% over the baseline values before dip consumption. A significant reduction (P<0.05) in the plasma triglyceride levels from 1.93 (1.08-2.09) mmol/l at baseline to 1.27 (0.93-2.22) mmol/l after 6 weeks was also apparent following the consumption of the n-3PUFA-enriched dip. Plasma cholesterol was unchanged; however, low-density lipoprotein (LDL)-cholesterol (2.46+/-0.21 versus 2.72+/-0.22 mmol/l, P<0.034) and high-density lipoprotein (HDL)-cholesterol (1.16+/-0.09 versus 1.22+/-0.09 mmol/l, P<0.042) were significantly increased following the dietary intervention. CONCLUSIONS: These results demonstrate that n-3PUFA are readily bioavailable from the fortified dip matrix and alter the plasma lipid profile.

Invited review: Amino acid bioavailability and digestibility in pig feed ingredients: terminology and application.

In this review, the terminology that is used to describe the bioavailability and ileal digestibility of AA in pig feed ingredients is defined. Aspects of the methodology to establish bioavailability and ileal digestibility values also are discussed, and recommendations about the use of these values are provided. Two main factors can contribute to differences between bioavailability and ileal digestibility of AA. First, some AA, such as Lys, may be absorbed in chemical complexes that preclude their use for metabolism. Second, fermentation in the upper gut may result in a net loss or gain of AA to the animal. In addition, dietary effects on the efficiency of using bioavailable AA intake for tissue growth or milk production should be considered and may be attributed to endogenous AA losses in the hindgut and the metabolic costs associated with endogenous gut protein synthesis and losses. Ileal digestibility values may be expressed as apparent ileal digestibility (AID), standardized ileal digestibility (SID), or true ileal digestibility (TID). These terms are used to specify how ileal endogenous AA losses are reflected in digestibility values. Ileal endogenous AA losses may be separated into basal losses, which are not influenced by feed ingredient composition, and specific losses, which are induced by feed ingredient characteristics such as levels and types of fiber and antinutritional factors. Values for AID are established when total ileal outflow of AA (i.e., the sum of endogenous losses and nondigested dietary AA) is related to dietary AA intake. A concern with the use of AID values is that these are not additive in mixtures of feed ingredients. This concern may be overcome by correcting AID values for defined basal endogenous losses of AA, which yields SID values. Furthermore, if the AID values are corrected for basal and specific endogenous losses, then values for TID are calculated. However, reliable procedures to routinely measure specific endogenous losses are not yet available. It is recommended that basal ileal endogenous losses of AA should be measured in digestibility experiments using a defined protein-free diet and that these losses are reported with observed AID and SID values. It is suggested that SID values should be used for feed formulation, at least until more information on TID values becomes available.

A genetic upper limit to whole-body protein deposition in a strain of growing pigs.

The genetic upper limit to daily whole-body protein deposition (Pdmax) is an important constraint on pig growth. The Pdmax was determined for a specified pig genotype using N balance and serial slaughter techniques. A traditional N-balance study, involving 36 and 90 kg of BW Large White x (Landrace x Large White) entire male pigs, was first conducted to demonstrate that a highly digestible, nutrient-dense diet (1.54% Lys; 18 MJ of DE/kg, air-dried basis) was able to support the attainment of Pdmax within the constraints of pig appetite. Animals were allocated to set levels of feed intake [set proportions of ad libitum DE intake (DEi), 50 to 100%]. Nitrogen retention increased linearly with DEi up to 25.3 and 35.2 MJ of DE/d for the 36 and 90 kg of BW pigs, respectively, then showed a departure (P < 0.05) from linearity. For DEi of the experimental diet above the latter intakes, which were approximately 80% of a determined ad libitum DEi, the pigs deposited protein at a rate approaching Pdmax. When a linear plateau response model (accepted a priori) was fitted, Pdmax values of 189.9 g/d at a DEi breakpoint of 28.3 MJ of DE/d at 36 kg of BW and 186.4 g/d at a DEi breakpoint of 37.3 MJ of DE/d at 90 kg of BW were found. In the serial slaughter study, 18 female and 18 entire male pigs were allocated to 5 slaughter BW (25, 45, 65, 85, and 110 kg) such that there were 5, 3, 3, 3, and 4 animals of each sex at each slaughter weight, respectively. Animals were fed the experimental diet ad libitum, and whole-body protein was determined at slaughter. Growth data were analyzed by differentiating and combining continuous mathematical functions for BW and body composition. The ad libitum DEi were 27.4 and 50.7 MJ/d at 36 and 90 kg of BW for the entire males and were assumed, based on the N-balance results, sufficiently high to allow expression of Pdmax. There was an effect (P < 0.05) of sex on Pdmax vs. time (days on trial). Over the BW range of 25 to 85 kg, Pdmax was constant for the entire male and female pigs at 170 and 147 g/d, respectively. Above 85 kg of BW, Pdmax was no longer constant for either sex.