Apparent ileal dry matter and crude protein digestibility of rations fed to pigs and determined with the use of chromic oxide (Cr2O3) and acid-insoluble ash as digestive markers

Effect of coated-benzoic acid on growth performance, immunity, and intestinal functions in weaned pigs challenged by enterotoxigenic Escherichia coli

Introduction

Benzoic acid (BA) could be added to the diets of weaned pigs to prevent diarrhea due to its antibacterial function. However, BA may be absorbed or decomposed before it can reach the hindgut. This study was conducted to explore the effect of a novel coated benzoic acid (CBA) on growth performance, immunity, and intestinal barrier functions in weaned pigs upon enterotoxigenic Escherichia coli (ETEC) challenge.

Methods

In a 21d experiment, 32 piglets were randomly assigned to 4 treatments: (1) a basal diet (CON), (2) CON added with CBA at 3  g/kg (CBA); (3) CON and challenged by ETEC (ECON); (4) CON added with CBA at 3 g/kg and challenged by ETEC (ECON). On d 22, all piglets were euthanised to obtain samples.

Results

Dietary CBA supplementation elevated the average daily gain (ADG) of the ETEC-challenged pigs (p < 0.05). CBA also improved the digestibility of dry matter, gross energy, and ash (p < 0.05). Moreover, CBA elevated the ratio of blood basophil and the serum concentration of total cholesterol of the ETEC challenged pigs (p < 0.05). Importantly, CBA increased the serum concentrations of immunoglobulin A (IgA), IgG, and IgM (p < 0.05). CBA not only decreased the crypt depth but also increased the ratio of villus height to crypt depth (V:C) in the jejunum and ileum (p < 0.05). Moreover, CBA increased the activities of jejunal and ileal sucrase, and the activities of duodenal and ileal maltase (p < 0.05). Importantly, CBA elevated the expression levels of critical functional genes such as the claudin-1, occluding, glucose transporter-2 (GLUT2), and sodium/glucose cotransporter-1 (SGLT-1) in the jejunal epithelium upon ETEC challenge (p < 0.05). Additionally, CBA increased the abundances of total bacteria and Bacillus, and increased the concentrations of volatile fatty acids (acetic acid, propanoic acid, and butyric acid) in cecum (p < 0.05).

Discussion

These results suggested a beneficial role for CBA in alleviating intestinal injury in weaned pigs following ETEC challenge. Such effects may be tightly associated with elevated immunity and improved intestinal epithelium functions and microbiota.

A blend of bacillus-fermented soybean meal, functional amino acids, and nucleotides improves nutrient digestibility, bolsters immune response, reduces diarrhea, and enhances growth performance in weaned piglets

This study investigated the effects of a blend of bacillus-fermented soybean meal, functional amino acids, and nucleotides (Functional protein blend-FP Blend) as a replacement for animal protein sources in a weaner pig diet without antibiotic growth promoters on nutrient digestibility, blood profiles, intestinal morphology, diarrhea incidence, and growth performance. A total of 288 crossbred weaned piglets [♂ Duroc x ♀ (Yorkshire × Landrace)] with an average body weight (BW) of 6.89 ± 0.71 kg were randomly allocated to 6 groups based on initial BW and sex (8 replicate pens per treatment; 3 gilts and 3 barrows/pen). The experiment lasted for 5 wk. Dietary treatments included PC [standard diet with 3% fish meal (FM) and 2% plasma protein (PP)], NC (nonanimal protein, AP), T1 (3% FM replaced with 5% FP Blend), T2 (3% FM and 1% PP replaced with 5% FP Blend), T3 (2% PP replaced with 5% FP Blend), and T4 (3% FM and 2% PP replaced with 5% FP Blend). Data were analyzed using Minitab version 17 software. Key results indicated that FP Blend improved the apparent ileal digestibility (AID) coefficient of dry matter, gross energy, lysine, and valine in T4 compared with NC treatment (P < 0.05), whereas AID coefficient of crude protein and other amino acids remained constant (P > 0.05). Compared with NC diet, the weaned pigs fed T4 diet reduced malondialdehyde, serum IL8, TNF-α, and increased IgG (P < 0.05), while showing no effect on serum IL6, IL10, white blood cells, IgA, and endotoxin (P > 0.05). Furthermore, FP blend significantly increased villus height in the duodenum and ileum in T4 compared with NC (P < 0.05). The average daily gain (ADG) was highest in T4 (502.73 g/d), followed by T1 (477.96 g/d) and T2 (475.85 g/d), compared with PC (450.86 g/d) and NC (439.79 g/d). T4's ADG significantly differed from PC and NC (P < 0.001), whereas no significant differences were observed in T1, T2, and T3 (P > 0.05). The feed conversion ratio (FCR) was significantly lower in T4 (1.45) compared with PC (1.57) and NC (1.59) (P < 0.001), with no significant differences among other groups. In conclusion, FP Blend demonstrated efficacy in improving nutrient digestibility, optimizing intestinal morphology, bolstering immune responses, reducing diarrhea incidence, alleviating the adverse effects of weaning stress, and enhancing growth performance of weaned piglets.

Mixed organic acids as an alternative to antibiotics improve serum biochemical parameters and intestinal health of weaned piglets

The primary aim of this experiment was to critically explore the relationship between the different levels of mixed organic acids (MOA) and growth performance, serum antioxidant status and intestinal health of weaned piglets, as well as to investigate the potential possibility of MOA alternative to antibiotics growth promoters (AGP). A total of 180 healthy piglets (Duroc × [Landrace × Yorkshire]; weighing 7.81 ± 1.51 kg each, weaned at d 28) were randomly divided into 5 treatments: 1) basal diet (CON); 2) CON + chlorinomycin (75 mg/kg) + virginiamycin (15 mg/kg) + guitaromycin (50 mg/kg) (AGP); 3) CON + MOA (3,000 mg/kg) (OA1); 4) CON + MOA (5,000 mg/kg) (OA2); 5) CON + MOA (7,000 mg/kg) (OA3). This study design included 6 replicates per treatment with 6 piglets per pen (barrow:gilt = 1:1) and the experiment was separated into phase 1 (d 1 to 14) and phase 2 (d 15 to 28). In phases 1, 2 and overall, compared with the CON, the feed conversion ratio (FCR) was reduced (P < 0.01) and the average daily gain (ADG) was increased (P < 0.05) in piglets supplemented with AGP, OA1 and OA2. The concentration of serum immunoglobulins G (IgG) was improved (P < 0.05) in piglets supplemented with OA2 in phase 2. In the jejunum and ileum, the villus height:crypt depth ratio was significantly increased (P < 0.01) in piglets fed AGP and OA1. The mRNA expression level of claudin-1 and zonula occludens-1 (ZO-1) (P < 0.01) was up-regulated in piglets supplemented with OA1 and OA2. The piglets fed AGP, OA1 and OA2 showed an increase (P < 0.05) in the content of acetate acid and total volatile fatty acids (TVFA) in the cecum, and butyric acid and TVFA in the colon compared with CON. Also, OA1 lowered (P < 0.05) the content of Lachnospiraceae in piglets. These results demonstrated that MOA at 3,000 or 5,000 mg/kg could be an alternative to antibiotics due to the positive effects on performance, immune parameters, and intestinal health of weaned piglets. However, from the results of the quadratic fitting curve, it is inferred that MOA at a dose of 4,000 mg/kg may produce a better effect.

Wheat bran fermented by mixed fungal strains improves the digestibility of crude fiber and may benefit the gut health without impacting the growth performance in weaned pigs

This study was conducted to compare the effect of raw (WB) or mixed fungi-fermented wheat bran (FWB) on the growth, nutrient digestibility and intestinal health in weaned piglets. After the preparation of FWB, twenty-one cross-bred weaned piglets (7.20 ± 0.5 kg) were separated into three groups for a 40-day trial. The pigs in the control group were fed a basal corn-soybean meal diet. For the other two groups, 8% of expanded corn in the basal diet was replaced by equivalent WB or FWB. Results showed that the content of main nutrients and the composition of dietary fiber in FWB improved compared to that for WB. The digestibility of fiber in pigs fed FWB improved (P < 0.05) compared to the control and/or WB without affecting their growth performance. Both WB and FWB decreased the conditional pathogen (Streptococcus) or/and E. coli virulence factor (STb) in the colon compared to control (P < 0.05), and the ratio of villus height to crypt depth (VCR) in jejunum increased (P < 0.05). The number of goblet cells, the expression of MUC-1 and pBD1 in jejunal mucosa, and the proportion of blood CD4⁺ T lymphocyte subset improved (P < 0.05) by FWB rather than WB. Furthermore, although only WB elevated (P < 0.05) the concentration of butyrate in the colon, both WB and FWB increased the number of butyrate-producing bacteria (P < 0.05) compared to the control. Thus, the main advantage of FWB over WB in weaned pigs is its improvement in fiber digestibility.

Acid-insoluble ash is a better indigestible marker than chromic oxide to measure apparent total tract digestibility in pigs

The aim of this study was to determine the apparent total tract digestibility (ATTD) of nutrients in cottonseed meal (CSM) and soybean meal (SBM) in simple carbohydrate and more complex wheat-based diets using 2 indigestible markers and total faecal collection. Twenty-five Large White × Landrace boars (57.8 kg) were randomly allocated to either a pure wheat diet, 40% CSM or SBM in either a sugar-starch- (1:1) or wheat-based diet for 18 d. Acid-insoluble ash (AIA) and chromic oxide (Cr2O3) were included in all diets as indigestible markers. Diets were offered (1,800 g/d per pig) in 3 meals/d from d 1 to 11 and 8 meals/d from d 12 to 17. On d 9, the pigs were moved to individual metabolism cages to allow total faecal collection. On d 18, the pigs were fed hourly for 8 h. After the 8th meal, pigs were anaesthetized and digesta sampled from the terminal ileum and rectum before lethal injection. There were no differences between ATTD of nitrogen (N) determined using AIA as a marker and measured by total faecal collection. On the other hand, the ATTD of N of diets containing CSM in sugar-starch- or wheat-based diets and the pure wheat diet determined using Cr2O3 as a marker was less (-3.11%, -4.46% and -6.59%; P < 0.001) than that measured by total faecal collection. The ATTD of N determined using AIA as a marker was highly correlated with that measured using total faecal collection (P < 0.001; R 2 = 0.95). Similarly, the ATTD of N determined using Cr2O3 as a marker was correlated with that measured using total faecal collection, although the correlation was not quite as strong as using AIA (P < 0.001; R 2 = 0.87). Also, the slope of the regression line and the intercept were closer to unity and zero for the relationship when the ATTD of N was determined using AIA compared to Cr2O3 as an indigestible marker. The ATTD of organic and dry matter behaved similarly. These data demonstrate that the basal diet and choice of indigestible marker can substantially influence the ATTD and that the use of AIA as an indigestible marker is more suitable than Cr2O3 in digestibility studies in pigs.

Effects of Dietary Starch Structure on Growth Performance, Serum Glucose-Insulin Response, and Intestinal Health in Weaned Piglets

Simple Summary

Carbohydrates are the most important energy source for monogastric animals, including humans, and dysregulation of carbohydrate metabolism has been associated with metabolic syndromes, such as type 2 diabetes mellitus (T2DM), hypertension, and obesity. Starch is the major carbohydrate source, consisting of amylose and amylopectin. This study investigated the effects of dietary starch structure on growth performance, serum glucose–insulin response, and intestinal health in weaned piglets, which may contribute to the principles of carbohydrate nutrition and facilitate the utilization of dietary starches.

Abstract

To investigate the effects of dietary starch structure (amylose/amylopectin ratio, AR) on serum glucose absorption metabolism and intestinal health, a total of ninety weaned piglets (Duroc × (Yorkshire × Landrace)) were randomly assigned to 5 dietary treatments and fed with a diet containing different AR (2.90, 1.46, 0.68, 0.31, and 0.14). The trial lasted for 21 d. In this study, the growth performance was not affected by the dietary starch structure (p > 0.05). Diets with higher amylose ratios (i.e., AR 2.90 and 1.46) led to a significant reduction of the serum glucose concentration at 3 h post-prandium (p < 0.01), while high amylopectin diets (AR 0.31 and 0.14) significantly elevated The expression of gene s at this time point (p < 0.01). High amylopectin diets also increased the apparent digestibility of crude protein (CP), ether extract (EE), dry matter (DM), gross energy (GE), and crude ash (p < 0.001). Interestingly, diet rich in amylose (AR 2.90) significantly elevated the butyric acid content (p < 0.05) and decreased the pH value (p < 0.05) in the cecal digesta. In contrast, diet rich in amylopectin (i.e., AR 0.14) significantly elevated the total bacteria populations in the cecal digesta (p < 0.001). Moreover, a high amylopectin diet (AR 0.14) tended to elevate the mRNA level of fatty acid synthase (FAS, p = 0.083), but significantly decreased the mRNA level of sodium-dependent glucose transporter 1 (SGLT1, p < 0.05) in the duodenal and jejunal mucosa, respectively. These results suggested that blood glucose and insulin concentrations were improved in high AR diets, and the diet also helped to maintain the intestinal health.

At least 3 days of adaptation are required before indigestible markers (chromium, titanium, and acid insoluble ash) are stabilized in the ileal digesta of 60-kg pigs, but values for amino acid digestibility are affected by the marker

An experiment was conducted to 1) test the hypothesis that a minimum adaptation period to diets used in ileal amino acid (AA) digestibility experiments with pigs is needed and 2) to test the null-hypothesis that ileal digestibility and basal endogenous losses of AA are not affected by the indigestible marker used. Eight ileal-cannulated barrows with an initial BW of 58.1 ± 4.3 kg were randomly allotted to a 2-period crossover design with 2 diets and 4 pigs per diet in each period. A soybean meal-based diet and an N-free diet were prepared. Both diets contained 0.4% chromium oxide, 0.4% titanium dioxide, and 0.4% Celite (a source of acid insoluble ash; AIA). Pigs were provided feed in a daily amount of 3 times the maintenance requirement for metabolizable energy, and 2 equal meals were provided each day. Ileal digesta samples were collected from 0800 to 2000 h on each day during the two 9-d collection periods. There was no period by diet interactions observed. Marker concentrations in ileal digesta were analyzed separately for each day, and the point where the concentration of each marker was stabilized in the digesta was determined using a linear broken-line analysis. For pigs fed the soybean meal diet, the breakpoints for Cr, Ti, and AIA in ileal digesta were 2.70, 2.45, and 3.77 d, respectively. In pigs fed the N-free diet, the breakpoints for Cr, Ti, and AIA in ileal digesta were 2.52, 2.39, and 2.29 d, respectively. Based on the pooled data, the basal endogenous losses of most AA calculated using Cr as an indigestible marker were less (P < 0.05) than the values calculated using Ti, but greater (P < 0.05) compared with values calculated based on AIA. The standardized ileal digestibility of most AA in soybean meal calculated using Cr or Ti as a digestibility marker were greater (P < 0.05) than the digestibility values calculated using AIA. In conclusion, 3 d of adaptation is required before markers are stabilized in the ileal outflow if Cr or Ti is used as an indigestible marker and 4 d of adaptation is required if AIA is the marker. Values for AA digestibility calculated using Cr or Ti as the marker are not different, but greater compared with values calculated using AIA as the marker.

Effects of Bacillus subtilis DSM32315 supplementation and dietary crude protein level on performance, gut barrier function and microbiota profile in weaned piglets1

Seventy-two piglets aged at 25 d were chosen to investigate the effects of Bacillus subtilis DSM32315 supplementation in diets with different protein levels on growth performance, intestinal barrier function, and gut microbiota profile in a 42-d trial. The animals were allotted to four treatment groups in a randomized complete block design involving a 2 (protein levels) × 2 (probiotic levels) factorial arrangement of treatments. Two protein levels included the high CP (HP) diets (0 to 14 d, 20.5%; 15 to 42 d, 19.5%) and the low CP (LP) diets (0 to 14 d, 18%; 15 to 42 d, 17%), and added probiotic (PRO) levels included at 0 and 500 mg/kg diet. Two interactions between CP and PRO for ADG (P < 0.01) and F/G (P < 0.05) were observed in phase 1. Within the piglets given the LP diet, probiotic supplementation increased ADG and decreased F/G ratio. Likewise, there were interactions between CP and PRO on the digestibility of CP (P < 0.01) and EE (P < 0.05), and probiotic supplementation increased the digestibility of CP and ether extract (EE) of piglets fed with LP diet, but that was not the case for piglets fed with HP diet. Furthermore, there were interactions between CP and PRO on villus height (P < 0.01) and villus height:crypt depth ratio (P < 0.05) in ileum. Piglets fed with LP diet containing probiotic had the greatest villus height and villus height:crypt depth ratio in ileum among treatments. There were also main effects of PRO on the propionic acid (P < 0.05) and butyric acid (P < 0.05), and the concentrations of propionic acid and butyric acid in colonic digesta were increased with the inclusion of probiotic in diet. Piglets fed with LP diet containing probiotic had the greatest population of Bacillus and Bifidobacterium (P < 0.05) in colon. In addition, there were interactions between CP and PRO on the mRNA expressions of occludin-1 (P < 0.05), epidermal growth factor (EGF) (P < 0.05), and insulin-like growth factor 1 receptor (IGF-1R) (P < 0.05). The LP fed piglets plus probiotic exhibited the greatest mRNA expressions of occludin-1, EGF, and IGF-1R in ileum compared with other treatments. In conclusion, moderate dietary protein restriction combining with the addition of B. subtilis DSM32315 synergistically increased growth performance, altered hindgut bacterial composition and metabolites, maintained intestinal barrier function in ileum of piglets.

Techniques for evaluating digestibility of energy, amino acids, phosphorus, and calcium in feed ingredients for pigs

Sound feed formulation is dependent upon precise evaluation of energy and nutrients values in feed ingredients. Hence the methodology to determine the digestibility of energy and nutrients in feedstuffs should be chosen carefully before conducting experiments. The direct and difference procedures are widely used to determine the digestibility of energy and nutrients in feedstuffs. The direct procedure is normally considered when the test feedstuff can be formulated as the sole source of the component of interest in the test diet. However, in some cases where test ingredients can only be formulated to replace a portion of the basal diet to provide the component of interest, the difference procedure can be applied to get equally robust values. Based on components of interest, ileal digesta or feces can be collected, and different sample collection processes can be used. For example, for amino acids (AA), to avoid the interference of fermentation in the hind gut, ileal digesta samples are collected to determine the ileal digestibility and simple T-cannula and index method are commonly used techniques for AA digestibility analysis. For energy, phosphorus, and calcium, normally fecal samples will be collected to determine the total tract digestibility, and therefore the total collection method is recommended to obtain more accurate estimates. Concerns with the use of apparent digestibility values include different estimated values from different inclusion level and non-additivity in mixtures of feed ingredients. These concerns can be overcome by using standardized digestibility, or true digestibility, by correcting endogenous losses of components from apparent digestibility values. In this review, methodologies used to determine energy and nutrients digestibility in pigs are discussed. It is suggested that the methodology should be carefully selected based on the component of interest, feed ingredients, and available experimental facilities.

Studies on cannulation method and alternative indigestible markers and the effects of food enzyme supplementation in barley-based diets on ileal and overall apparent digestibility in growing pigs

Two different cannulation procedures (simple ileal ‘T’ cannula v. The post valve ‘T’ caecal cannula (PVTC)) and two indigestible markers (TiO2 v. Cr2O3) were studied with six male littermate pigs fitted with PVTC or simple ileal ‘T’ cannulae. Six diets were used, of which two were based on wheat and wheat bran and the other four were based on two barleys of different bushel weight without and with exogenous enzymes (ß-glucanase/xylanase). Proportional TiO2 and Cr2O3 recoveries in faeces were less than 1·00, the mean values for the six diets being 0·858 for TiO2 and 0·811 for Cr2O3. With both markers, recovery in faeces was lowest for the most digestible wheat-based diet (A). The ileal apparent digestibility (IAD) coefficients of dry matter (DM), crude protein (CP), energy and amino acids measured with Cr2O3 were significantly (P < 0·001) lower than those measured with TiO2. There was no difference in overall apparent digestibility of DM, CP and energy measured with simple ileal ‘T’ cannula and PVTC techniques. However, IAD of DM, energy and CP measured with the PVTC method were significantly higher than those measured with the simple ileal ‘T’ cannula method. The data also showed that the standard errors with the simple ileal ‘T’ cannula method were greater than when using the PVTC method. Diet significantly affected ileal and overall digestibility of nutrients (P < 0·001) with values being highest for diet A and least for the wheat bran-based diet (B). Overall digestibility (OD) of DM and energy were higher for the higher bushel weight barley-based diet (C) than for the normal bushel weight barley-based diet (E). Enzyme inclusion improved OD for both barley diets and ileal digestibility of energy (0·060) and CP (0·057) for the normal bushel weight barley.

Effects of xylanase and antibiotic addition on ileal and faecal apparent digestibilities of dietary nutrients and evaluating HCl-insoluble ash as a dietary marker in growing pigs

The effects of xylanase and antibiotic addition to the diet, and the use of HCl-insoluble ash as a marker, on ileal and faecal apparent digestibilities of nutrients were studied with 12 growing pigs fitted with post-valvular T-caecum cannulae (PVTC). The results showed that the apparent ileal digestibility of non-starch polysaccharide (NSP) was high, (over 0·30). Xylanase, or antibiotics (Avoparcin) or xylanase plus antibiotics supplementation of the wheat middling-based diets did not significantly (P > 0·05) increase the ileal and faecal apparent digestibilities of NSP, neutral-detergent fibre (NDF), dry matter, crude protein, energy or amino acids. There were no significant (P > 0·05) differences between the HCl-insoluble ash and Cr2O3 recoveries at the ileal or at the faecal levels: proportionately, 0·864 and 0·911 for the ileal and faecal recoveries of HCl-insoluble ash, and 0·857 and 0. 915 for the ileal and faecal recoveries of Cr2O3, respectively.

Effects of benzoic acid (VevoVitall®) on the performance and jejunal digestive physiology in young pigs

Background

As a organic acid, benzoic acid has become one of the most important alternatives for antibiotics, and its beneficial effect on performance in animals has been proven for a decade. However, knowledge of the effects of benzoic acid on jejunal digestive physiology, especially the antioxidant capacity and mucosal glucagon-like peptide 2 (GLP-2) concentrations is lacking.

Methods

A total of 20 barrows [Duroc × (Yorkshire × Landrace)] with an average body weight (BW) of 18.75 ± 0.2 kg were used in a 14-d trial to determine the potential mechanisms of benzoic acid supplementation on the performance, nutrient digestibility and jejunal digestive physiology in young pigs. All pigs were randomly allotted to 1 of 2 diets supplemented with 0 or 5000 mg/kg benzoic acid.

Results

Relative to the control, benzoic acid supplementation increased the average daily feed intake (ADFI), and average daily gain (ADG) in young pigs (P < 0.05), improved the apparent total tract digestibility of dry matter (DM), crude protein (CP), ether extract (EE), gross energy (GE) and crude ash (P < 0.05), and enhanced the activities of trypsin, lipase and amylase in the jejunum (P < 0.05). Similarly, relative to the control, supplementing benzoic acid in the diet resulted in a trend to reduce the pH values of the digesta (P = 0.06), decreased crypt depth and increased the villus height to crypt depth ratio (P < 0.05) in the jejunum of pigs. Finally, benzoic acid supplementation increased the mRNA expression and concentration of glucagon-like peptide 2 and the activities of glutathione peroxidase and superoxide dismutase in the jejunal mucosa of young pigs (P < 0.05).

Conclusions

In conclusion, supplementation with 5000 mg/kg benzoic acid improved the performance of young pigs through promoting nutrient digestion, improving jejunal antioxidant capacity, and maintaining the jejunal morphology in young pigs.

Chromic oxide and acid-insoluble ash as markers in digestibility studies with growing pigs and sows

The results of three experiments, focused on the determination of endogenous ileal flow (EIF) of amino acids (AA) and nitrogen (N) (Exp. 1), apparent ileal digestibility (AID) of AA and N (Exp. 2), and apparent total tract digestibility (ATTD) of dry matter (DM), organic matter (OM), N, calcium (Ca) and phosphorus (P) (Exps. 2 and 3), were used to compare chromic oxide (Cr₂ O₃ ) and acid-insoluble ash (AIA) as digestibility markers. In Exps. 1 and 2, a total of six gilts fitted with T-cannula in terminal ileum, and in Exp. 3, a total of 24 pregnant sows were used. In Exps. 1 and 2, the pigs were assigned into four dietary treatments according to 4 × 6 crossover design (Exp. 1; diets with 0%, 4%, 8% and 12% of casein; Exp. 2 basal diet with different levels of phytase). In Exp. 3, the sows were assigned to four dietary treatments (basal diet with different levels of phytase) of six sows. In Exps. 1 and 2 ileal digesta and in Exps. 2 and 3 faeces were collected for the determination of EIF, AID and ATTD. Differences in EIF of AA determined by Cr₂ O₃ and AIA ranged (p ˃ 0.05) from -4.62 to 4.54%. The lowest EIF was for methionine and the greatest one for proline, determined by both markers. Apparent ileal digestibility determined by Cr₂ O₃ was slightly greater (p ˃ 0.05) in comparison with AIA. Differences ranged from 1.88% (Arg) to 7.08% (Gly). The greatest AID was for arginine and the lowest one for glycine, determined by both Cr₂ O₃ and AIA. Similarly for ATTD of DM, OM, N, Ca and P, there were no differences in digestibility determined by Cr₂ O₃ and AIA. Both, Cr₂ O₃ and AIA, are suitable and comparable markers for digestibility studies in pigs.

Short communication: Evaluation of acid-insoluble ash and indigestible neutral detergent fiber as total-tract digestibility markers in dairy cows fed corn silage-based diets

The objective of this experiment was to evaluate acid-insoluble ash (AIA) and indigestible NDF (iNDF) as intrinsic digestibility markers in comparison with total fecal collection (TC) in dairy cows fed corn silage- and alfalfa haylage-based diets. The experiment was part of a larger experiment, which involved 8 Holstein cows [102±28.4 d in milk, 26.4±0.27 kg/d of dry matter (DM) intake, and 43±5.3 kg/d milk yield]. The experimental design was a replicated 4×4 Latin square with the following treatments: metabolizable protein (MP)-adequate diet [15.6% crude protein (CP); high-CP], MP-deficient diet (14.0% CP; low-CP), and 2 other low-CP diets supplemented (top-dressed) with ruminally protected Lys or Lys and Met. Data for the 3 low-CP diets were combined for this analysis. Total feces were collected for 5 consecutive days during each period to estimate total-tract apparent digestibility. Digestibility was also estimated using AIA (digestion with 2 N HCl) and iNDF (12-d ruminal incubation in 25-μm-pore-size bags). Significant diet × digestibility method interactions were observed for fecal output of nutrients and digestibility. Fecal output of nutrients estimated using AIA or iNDF was lower compared with TC and fecal output of DM, organic matter, and CP tended to be higher for iNDF compared with AIA for the high-CP diet. For the low-CP diet, however, fecal output of all nutrients was lower for AIA compared with TC and was higher for iNDF compared with TC. Data from this experiment showed that, compared with TC, AIA underestimated fecal output and overestimated digestibility, particularly evident with the fiber fractions and the protein-deficient diet. Compared with TC, fecal output was overestimated and digestibility of the low-CP diet was underestimated when iNDF was used as a marker, although the magnitude of the difference was smaller compared with that for AIA. In the conditions of the current study, iNDF appeared to be a more reliable digestibility marker than AIA in terms of detecting dietary differences in apparent digestibility of some nutrients, but significant diet × marker interactions existed that need to be considered when estimating total-tract digestibility using intrinsic markers.

Advantages and limitations of the protein digestibility-corrected amino acid score (PDCAAS) as a method for evaluating protein quality in human diets

PDCAAS is a widely used assay for evaluating protein quality. It is a chemical score, which is derived from the ratio between the first limiting amino acid in a test protein and the corresponding amino acid in a reference amino acid pattern and corrected for true faecal N digestibility. Chemical scores exceeding 100 % are truncated to 100 %. The advantages of the PDCAAS are its simplicity and direct relationship to human protein requirements. The limitations are as follows: the reference pattern is based on the minimum amino acid requirements for tissue growth and maintenance and does not necessarily reflect the optimum intake. Truncated PDCAAS of high-quality proteins do not give any information about the power of these proteins to compensate, as a supplement, for low levels of dietary essential amino acids in low-quality proteins. It is likely that faecal N digestibility does not take into account the loss from the colon of indispensable amino acids that were not absorbed in the ileum. Anti-nutritional factors, such as lectins and trypsin inhibitors, in several plant protein sources can cause heightened endogenous losses of amino acids, an issue which is particularly relevant in animal feedstuffs. The assumption that amino acid supplementation can completely restore biological efficiency of the protein source is incorrect since the kinetics of digestion and absorption between supplemented free amino acids and amino acids present in dietary proteins, are different.

Feed ingredients differing in fermentable fibre and indigestible protein content affect fermentation metabolites and faecal nitrogen excretion in growing pigs

To study the fermentation characteristics of different non-conventional dietary fibre (DF) sources with varying levels of indigestible CP content and their effects on the production of fermentation metabolites and on faecal nitrogen (N) excretion, an experiment was conducted with 40 growing pigs (initial BW 23 kg) using wheat bran (WB), pea hulls (PH), pea inner fibres (PIF), sugar beet pulp (SBP) or corn distillers dried grains with solubles (DDGS). The diets also contained soya protein isolate, pea starch and sucrose, and were supplemented with vitamin-mineral premix. Faecal samples were collected for 3 consecutive days from day 10, fed with added indigestible marker (chromic oxide) for 3 days from day 13 and pigs were slaughtered on day 16 from the beginning of the experiment. Digesta from the ileum and colon were collected and analysed for short-chain fatty acids (SCFA) and ammonia (NH3) content. The apparent total tract N digestibility was the lowest (P < 0.001) in diets based on DDGS (74%), medium in diets with WB and SBP (76% each) and highest in those with PIF and PH (79% and 81%, respectively). Expressed per kg fermented non-starch polysaccharides (NSP), faecal N excretion was higher with DDGS and WB diets (130 and 113 g/kg NSP fermented, respectively) and lower with PIF, PH and SBP diets (42, 52 and 55 g/kg NSP fermented, respectively). The PH-based diets had the highest (P < 0.05) SCFA concentrations, both in the ileum and the colon (27 and 122 mMol/kg digesta, respectively). The highest NH3 concentration was also found in the colon of pigs fed with PH (132 mMol/kg digesta). Loading plot of principle component analysis revealed that the CP : NSP ratio was positively related with faecal N excretion and NH3 concentration in colon contents, whereas negatively related with SCFA concentration in colon contents. In conclusion, pea fibres and SBP increased SCFA and reduced NH3 concentration in the pig's intestine and reduced faecal N excretion, which makes pea fibres and SBP an interesting ingredient to use in pig diet to improve the positive effect of DF fermentation on the gastrointestinal tract and reduce faecal N excretion.

Ileal digestibility of dietary protein in the growing pig and adult human

The suitability of the pig as an animal model for predicting protein digestibility in man was evaluated. Healthy adult human subjects (mean body weight 67 kg;n11) and growing pigs (mean body weight 40 kg;n15) were fed semi-synthetic mixed meals containing, as a sole source of N, casein (C), hydrolysed casein (HC) or rapeseed isolate (R). There was no prior adaptation to the test meal. Ileal digesta were sampled through a naso-ileal tube (human subjects) or a post-valve T-caecum cannula (pigs) after ingestion of a bolus meal. The protein sources were15N-labelled. Amino acid (AA) digestibilities were not determined for R. Ileal apparent N digestibility was markedly lower (14–16 %;P < 0·001) in human subjects than in pigs (C, HC, R). Similarly, most apparent ileal AA digestibilities were lower (8 % on average;P < 0·05) in human subjects (C, HC). Ileal true N digestibility was slightly lower (3–5 %;P < 0·001) in human subjects than in pigs (C, HC, R) and most true ileal AA digestibilities were similar (P>0·05) between the species (C, HC). Exceptions were for phenylalanine, tyrosine, lysine, histidine and aspartic acid for which digestibilities were lower (3 % on average;P < 0·001) in human subjects. A similar ranking of the diets was observed for true ileal N digestibility between species. The inter-species correlation for true ileal digestibility was high for N (r0·98 over 3 × 2 data;P = 0·11) and AA (r0·87 over 26 × 2 data;P < 0·0001). Overall, this supports the use of the pig as a model for predicting differences among dietary protein digestibility, especially regarding true ileal N digestibility, in man.

A casein hydrolysate does not enhance gut endogenous protein flows compared with intact casein when fed to growing rats

We studied the effect of dietary free peptides vs. peptides released naturally during digestion on gut endogenous nitrogen (N) flow (ENFL) and amino acid (AA) flow (EAAFL). Semisynthetic diets containing 110 g/kg diet of the same casein, intact (C) or hydrolyzed (HC), were formulated with TiO2 as a dietary marker. Sprague-Dawley rats were fed the diets hourly (0800-1500 h) for 10 min each hour for 7 d. Rats received unlabeled diets for 6 d and 15N-labeled diets on d 7, whereby they were killed and digesta sampled (6 observations per group) along the intestinal tract. EAAFL and ENFL were determined by 15N-isotope dilution (ID) for C or by ID or after centrifugation and ultrafiltration (UF) for HC. Ileal EAAFL and ENFL (ID) were not enhanced with diet HC compared with diet C. The AA compositions (g/16 g N) of ileal ENFL did not differ between rats fed HC and C except for Asp, Phe, Tyr, and Ser, for which contributions were relatively lower (P < 0.05) for rats fed C. Ileal EAAFL and ENFL (HC) were considerably lower (P < 0.05) with ID than with UF, but flows of Gly, Phe, and His were similar. There was no stimulatory effect of dietary peptides from HC on endogenous ileal protein flow compared with C, but the result is tentative given the high degree of dietary N recycled within endogenous protein and which could have occurred at a differential rate between rats fed diets C and HC.

Sites of nutrient digestion in growing pigs: Effect of dietary fiber1

The impact of dietary fiber on fecal digestion is well-known and provides a comprehensive approach toward nutrient digestibility and availability. Little quantitative information is available on digestion of fiber in the different segments of the gastrointestinal tract (GIT). The objectives of this study were to obtain a method allowing the quantification of the digestive process in different segments of the GIT and to study the impact of dietary fiber on nutrient digestibility. Six barrows (average initial BW of 30 kg and fitted with a simple T-cannula at the proximal duodenum and caudal ileum) were used in a replicated 3 x 3 Latin square design. In each period, pigs were offered 1 of 3 diets differing in fiber content (low, medium, and high). Differences in fiber content were created by replacing wheat and barley with wheat bran. Titanium dioxide was included in the diet as an indigestible marker to determine the apparent digestibility coefficients in different segments of the GIT. The apparent digestibility of ash, CP, DM, and OM increased in the different segments of the GIT. Duodenal digestibility coefficients were negative for ash (e.g., -39.9% for the medium- and high-fiber diets), indicating important endogenous mineral secretions by the stomach and digestive glands. The duodenal digestibility of other nutrients and OM were positive but close to zero and numerically lower in the diets with the greater fiber contents. The fiber content in the diet did not affect the apparent ileal digestibility of nutrients. Increasing the fiber content in the diet affected the fecal digestibility of CP, ether extract, and energy (P < 0.01). The method used for studying sites of digestion in the digestive tract provides promising results, but it is limited due to the high variability that is likely caused by sampling limitations and variation between animals.

Utilização de indicadores para estimar a digestibilidade aparente em gatos

Compararam-se os métodos de coleta total (CT) e dos indicadores óxido crômico (Cr2O3), cinzas insolúveis em ácido (CIA) e lignina na determinação dos coeficientes de digestibilidade aparente (CDA) dos nutrientes para gatos. Os CDA de quatro rações foram determinados pela CT e estimados pelos diferentes indicadores em teste. Foram utilizados 24 gatos adultos castrados, alojados em gaiolas metabólicas individuais, totalizando seis animais por ração. O experimento seguiu um delineamento inteiramente ao acaso, em parcelas subdivididas, sendo as rações as parcelas, os métodos as subparcelas e cada gato uma unidade experimental. Os CDA foram significativamente menores pelo método da lignina em uma das rações estudadas (P<0,05). Os métodos Cr2O3, CIA e CT resultaram em CDA iguais em todas as rações (P>0,05). As taxas de recuperação dos indicadores, médias±erro-padrão da média, foram, respectivamente, de 97,1±2,5%, 97,3±2,9% e 83,9±9,1% para o Cr2O3, CIA e lignina. A CIA e o Cr2O3 mostraram grande potencial para utilização como indicadores, enquanto a ampla variabilidade dos resultados obtidos com a utilização da lignina não justificou seu emprego como substância índice para felinos.

Optimum ratio of histidine in the piglet ideal protein model and its effects on body metabolism. I. Basal diet formulation based on digestible amino acids according to the ideal protein model for 10 to 20 kg piglets

A 4 x 4 Latin square design was used to determine ileal apparent digestibility of amino acids (AAs) in corn, soybean meal, feather meal and dried whey in young pigs. The data were then to be used in formulating a basal diet for studies on AA metabolism in young pigs. Eight castrates T-cannulated at terminal ileum (average initial body weight 12.5 +/- 0.62 kg) were divided into 4 groups on the basis of body weight and transferred to individual metabolism crates. They were then fed four experimental diets containing the four feedstuffs to be tested (corn, soybean meal, feather meal and dried whey). The trial lasted 20 days, which included 4 five-day periods for ileal digesta collection. It was found that the digestibility of the AAs was similar to that reported in literature. Based on the findings a basal diet for this research was formulated according to an ideal protein model for the 10 to 20 kg piglet, on the basis of digestible AAs and containing 14.13 MJ/kg digestible energy, 18.22% crude protein, 1.04% digestible lysine and 0.23% digestible histidine.

Coeficientes de digestibilidade aparente pelos métodos de indicadores e coleta total de fezes em cães

Foram avaliados comparativamente os métodos de coleta total de fezes (CT) e de indicadores, óxido crômico (Cr2O3), fibra em detergente ácido (FDA) e cinzas insolúveis em ácido (CIA), para determinação dos coeficientes de digestibilidade aparente (CDA) da matéria seca, proteína bruta, extrativos não nitrogenados e energia bruta de um alimento comercial para cães. Cinco cães adultos, machos, sem raça definida e com média de peso de 13,84kg receberam diariamente 2g de Cr2O3, divididos em duas porções de 1g, administradas por meio de cápsulas de gelatina por um período de 14 dias. Os sete primeiros dias foram de adaptação e os sete dias subseqüentes de coleta de fezes. Os métodos de CT, de Cr2O3 e de CIA não apresentaram diferenças entre si (P>0,001) e podem ser utilizados para determinação dos coeficientes de digestibilidade aparente na espécie canina. O indicador FDA apresentou menor índice de recuperação do que os indicadores CIA e Cr2O3 e seus resultados não apresentaram equivalência com os obtidos por outros métodos testados. As médias (+ desvio padrão) dos índices de recuperação foram 55,1% (+3,7), 93,9% (+ 17,7) e 93,7% (+ 13,3) para FDA, CIA e Cr2O3, respectivamente.

Torpor and digestion in food-storing hibernators

Many species of hibernating mammals rely on hoarded food rather than body fat to support winter energy requirements. Here, we evaluate whether the associated ingestive and digestive requirements reduce the benefits that food-storing hibernators can accrue from torpor. Using a simple model, we predict (1) that digestive efficiency could either increase or decrease with increased use of torpor, depending on the Q(10) of digestion relative to the Q(10) of whole-animal metabolism and (2) that increased torpor will result in a linear decrease in energy consumption but an exponential increase in euthermic intake requirements. In 16 captive eastern chipmunks (Tamias striatus), the proportion of time that different individuals spent in torpor was highly variable (29.8%+/-5.9%; 0.0%-86.3%), positively correlated with dry matter digestibility (r2=0.53, P=0.02) and negatively correlated with energy consumption (r2=0.72, P=0.002). Thus, by both increasing conversion efficiency and reducing energy requirements, torpor appears to provide a double benefit for energy conservation by food-storing hibernators. Despite this, a comparative analysis shows that the euthermic intervals of food-storing rodents are four times as long and torpor intervals are half as long as that of fat-storing rodents. Given that required euthermic intake rates are expected to increase exponentially at high levels of torpor, the reduced torpor expression of food-storing species may result from constraints on their ability to load enough food into the gut when euthermic to cover the energy requirements of the subsequent torpor cycle.

The protein digestibility-corrected amino acid score

The protein digestibility-corrected amino acid score (PDCAAS) has been adopted by FAO/WHO as the preferred method for the measurement of the protein value in human nutrition. The method is based on comparison of the concentration of the first limiting essential amino acid in the test protein with the concentration of that amino acid in a reference (scoring) pattern. This scoring pattern is derived from the essential amino acid requirements of the preschool-age child. The chemical score obtained in this way is corrected for true fecal digestibility of the test protein. PDCAAS values higher than 100% are not accepted as such but are truncated to 100%. Although the principle of the PDCAAS method has been widely accepted, critical questions have been raised in the scientific community about a number of issues. These questions relate to 1) the validity of the preschool-age child amino acid requirement values, 2) the validity of correction for fecal instead of ileal digestibility and 3) the truncation of PDCAAS values to 100%. At the time of the adoption of the PDCAAS method, only a few studies had been performed on the amino acid requirements of the preschool-age child, and there is still a need for validation of the scoring pattern. Also, the scoring pattern does not include conditionally indispensable amino acids. These amino acids also contribute to the nutrition value of a protein. There is strong evidence that ileal, and not fecal, digestibility is the right parameter for correction of the amino acid score. The use of fecal digestibility overestimates the nutritional value of a protein, because amino acid nitrogen entering the colon is lost for protein synthesis in the body and is, at least in part, excreted in urine as ammonia. The truncation of PDCAAS values to 100% can be defended only for the limited number of situations in which the protein is to be used as the sole source of protein in the diet. For evaluation of the nutritional significance of proteins as part of mixed diets, the truncated value should not be used. In those cases, a more detailed evaluation of the contribution of the protein to the amino acid composition of the mixed diet is required. From such an evaluation, it appears that milk proteins are superior to plant proteins in cereal-based diets.

Nutritional and physiological criteria in the assessment of milk protein quality for humans

Dietary protein quality is influenced by several factors and especially amino acid composition as well as the bioavailability of the protein. The method to assess the dietary protein quality recommended by the FAO/WHO (1985, 1990) is based on the ability of the protein to satisfy the indispensable amino acid requirements. The Protein Digestibility Corrected Amino Acid Score (PD-CAAS) has been proposed as a quality index and takes into account both the indispensable amino acid composition and the protein digestibility. This index can easily be used routinely, but some conceptual and methodological limits must be considered, such as the determination of both nitrogen and indispensable amino acid requirements, the bioavailability of dietary protein and the validation of the quality indexes. Another level in the evaluation of protein quality considers more specific activities related to specific protein-derived components. The compounds responsible for these activities include enzymes, immunoglobulins, mediator and hormone-like substances. These actions are linked to native proteins or to peptides cleaved from protein during digestion.