Estimates of dietary threshold levels for crude protein and amino acids to obtain plateau values of apparent ileal crude protein and amino acid digestibilities in newly weaned pigs

This study was conducted to estimate dietary threshold levels for crude protein (CP) and amino acids (AA) at which apparent ileal digestibilities (AID) of CP and AA in assay diets for newly weaned pigs reach plateaus. A total of 14 (12 + 2 for replacement) three-week old barrows were fitted with simple T cannulas at the distal ileum. Corn starch-based diets containing six graded levels of CP from casein, 90, 155, 220, 285, 350, or 415 g CP/kg assay diet (as-fed), were formulated. At 28 days of age, the pigs were randomly allocated to the six dietary treatments with two pigs per CP level in four weekly repeated measurement periods. They were fed twice daily a total of 30 g (as-fed) per kg of individual body weight at 8:00 and 20:00 h. The dietary CP and AA levels affected AID of CP and most AA (p = 0.005 to p = 0.040) in the assay diets. The AID of CP and AA were higher at 155 and 220 compared to 90 g CP/kg assay diet (p < 0.001 to p = 0.047). Initially, the AID of CP and AA increased sharply then gradually reached, at individual break points (p < 0.001 to p = 0.047), their plateaus (p < 0.001), which did not change up to dietary CP levels of 415 g/kg assay diet and the AID values became independent of the dietary AA levels. The piglets' capacity to digest CP and absorb AA was not limiting under these experimental conditions. There was no effect of age on AID of CP and AA (p = 0.056 to p = 0.899) except for a linear increase (p = 0.045) in AID of glycine from Period 1 to 4. Segmented quadratic with plateau relationships between the AID of CP and AA and their dietary contents were fitted for CP and each AA. The lower end points of 95% confidence intervals of the plateau AID values were defined to represent the initial plateau AID. The dietary CP and AA contents, corresponding to the initial plateau AID values, represent the dietary threshold levels. For CP and the indispensable amino acids, the plateau AID [%] and the dietary threshold levels [g/kg DM], respectively, in casein were: CP, 94.2 and 176; arginine, 95.1 and 7; histidine, 96.0 and 5; isoleucine, 96.4 and 8; leucine, 96.8 and 16; lysine, 96.8 and 12; methionine, 97.9 and 5; phenylalanine, 96.2 and 10; threonine, 93.4 and 9; tryptophan, 94.3 and 2; valine, 95.9 and 11. For the determination of plateau AID in piglets, the crude protein and amino acid contents in the assay diets should meet or exceed the corresponding dietary threshold levels.     

Dietary supplementation with Chinese herbal powder enhances ileal digestibilities and serum concentrations of amino acids in young pigs

This study was designed to determine the effect of ultra-fine Chinese herbal powder as a dietary additive on serum concentrations and apparent ileal digestibilities (AID) of amino acids (AA) in young pigs. In Experiment 1, 60 Duroc x Landrace x Yorkshire piglets weaned at 21 days of age were randomly assigned to one of three treatments, representing supplementation with 0 or 2 g/kg of the powder, or 0.2 g/kg of colistin (an antibiotic) to corn- and soybean meal-based diets (n = 20 per group). Blood samples from five piglets per group were collected on days 7, 14, and 28 to determine serum AA concentrations. In Experiment 2, 12 barrows with an average initial body weight of 7.64 kg were randomly assigned to one of the three dietary treatments, followed by surgical placement of a simple T-cannula at the terminal ileum. All of the diets contained 0.1% titanium oxide as a digestibility marker. The samples of terminal ileal digesta were collected on day 7 for determining AID of AA. Results show that dietary supplementation with the herbal powder increased (P < 0.05) serum concentrations and AID of most AA by 10-50% and 10-16%, respectively. As an indicator of improved intestinal function, AID values of calcium were also enhanced in piglets supplemented with the herbal powder. Dietary supplementation of colistin increased serum concentrations and AID values of some AA by 8-44% and 10-15%, respectively, in comparison with the non-supplemented group. These novel findings demonstrate that the herbal powder can enhance the digestibility of dietary protein and the intestinal absorption of AA into the systemic circulation in post-weaning pigs, therefore providing a new mechanism for its growth- and immunity-promoting efficacy.     

Dietary supplementation with <Emphasis Type="Italic">Astragalus</Emphasis> polysaccharide enhances ileal digestibilities and serum concentrations of amino acids in early weaned piglets

Two experiments were conducted to evaluate the effects of dietary supplementation with Astragalus polysaccharide (APS) on growth performance, apparent ileal digestibilities (AID) of amino acids (AA), and their serum concentrations in early weaned piglets. In Exp. 1, 60 pigs were weaned at 21 days of age (BW 7.35 ± 0.23 kg) and allocated to three treatments (20 pigs/treatment), representing supplementing 0.0% (control), 0.02% colistin (antibiotic), or 0.1% APS to a corn- and soybean meal-based diet. Average daily gain (ADG), average daily feed intake (ADFI), and feed/gain ratio (F/G) were measured weekly. Blood samples were obtained from five pigs selected randomly from each treatment for the measurement of serum free AA concentrations on days 7, 14, and 28. In Exp. 2, 12 pigs were weaned at 21 day of age (BW 7.64 ± 0.71 kg), assigned to three treatment groups as in Exp. 1, and surgically fitted with a simple T-cannula at the terminal ileum. Ileal digesta samples were obtained for the measurement of AID of AA on days 7, 14 and 28. Dietary APS did not affect ADFI, but enhanced (P < 0.05) ADG by 11 and 4.4%, and improved F/G by 5.6 and 8.4%, respectively, compared with the control and antibiotic groups. Addition of APS to the diet increased AID and serum concentrations of most nutritionally essential and non-essential AA (including arginine, proline, glutamate, lysine, methionine, tryptophan, and threonine) on days 14 and 28. Circulating levels of total AA were affected by the age of pigs and treatment × time interaction. Collectively, these findings indicate that APS may ameliorate the digestive and absorptive function and regulate AA metabolism to beneficially increase the entry of dietary AA into the systemic circulation, which provide a mechanism to explain the growth-promoting effect of APS in early weaned piglets.     

Growth-promoting Activity of an Aqueous Extract of Soybean Seeds for Some Microorganisms

The metabolic fates of the carbon skeletons of leucine, lysine, and threonine were studied in growing rats on the diets containing graded levels of protein calorie percentages (10, 20, 30, and 40PC%) by use of either gluten or zein at 4100 kcal of metabolizable energy per kg of diets. In growth experiment for 21 days, body weight gain, food intake, and body fat increased at higher PC% in the gluten diets, but rats given zein did not maintain their initial weight even at 40PC%. The concentration of plasma free lysine remained low with the zein diets, but plasma threonine increased at 10 and 20PC% in the gluten and zein diets, respectively. Plasma leucine increased as the protein level increased either dietary protein. More than 70% of ¹⁴C was incorporated into body protein 12 h after an intraperitoneal injection of labeled lysine in all groups, but little ¹⁴CO₂ was expired in rats on the gluten and zein diets. About 79% of ¹⁴C-threonine was incorporated into body protein in rats given the gluten and zein diets at 10PC%, but the values were gradually decreased with increasing the dietary protein levels. Some 40–50% of ¹⁴C-leucine was incorporated into the body protein in rats given the gluten diets, and the values for the zein diets were extensively decreased in the higher PC% groups where the expired ¹⁴CO₂ was inversely increased to a great extent. These results showed that, when a specific amino acid was limiting or deficient in the diet, the major portion of the labeled amino acid was utilized for body protein synthesis and little was oxidized to carbon dioxide, whereas the oxidative degradation of essential amino acid other than limiting one was increased and the efficiency of the amino acid utilization was relatively decreased.     

Apparent Precaecal Digestibility of Nutrients and Level of Endogenous Nitrogen in Digesta of the Small Intestine of Growing Pigs as Affected by Various Digesta Viscosities

Sixteen male growing pigs of about 24kg BW were fitted with both a duodenal re-entrant and a post-valve T-shaped cannula inserted in the caecum. The animals were divided into four groups. Each group received one of the following diets: corn starch-soybean protein isolate-based diet without (diet C) and with carboxymethylcellulose (diet CMC) or a rye-wheat-based diet without (diet RW) and with xylanase addition (diet RWX). The diets provided similar levels of apparent precaecal digestible crude protein (CP), lysine, methionine+cystine, threonine and tryptophan. Additionally, [¹⁵N]-yeast was given with the diets during the first 10 days of the experiment. For estimation of digesta viscosity, N-flow of dietary and endogenous origin, apparent precaecal digestibilities of dry matter (DM), CP, amino acids and non starch polysaccharides (NSP) (only in pigs fed diets RW and RWX), ileal and duodenal digesta were quantitatively collected on day 16 and 17, respectively. The endogenous N-proportion was measured by the ratio of ¹⁵N enrichment in the digesta and urine. The duodenal and ileal digesta supernatant viscosity increased as carboxymethylcellulose was included into the diet. Xylanase addition to the rye-wheat based diet reduced the viscosity in the ileal digesta. There were no differences in precaecal digestibilities of DM, CP and amino acids between diet C and CMC. The precaecal digestibilities of DM and soluble and insoluble NSP increased from 69.5% to 73.9%, from 1.3% to 47.9% and from 17.0% to 35.4%, respectively, as xylanase was added to the rye-wheat-based diet. The apparent precaecal digestibility of most essential amino acids increased by 2 to 5 percent units. The amounts of endogenous N at the duodenal level were estimated to be 158, 233, 313 and 276mg per 12h per kg^0.75 BW of pigs fed diets C, CMC, RW and RWX, respectively. The corresponding values at the ileal level were 95, 107, 164 and 150mg per 12h per kg^0.75 BW. For endogenous N amounts, significant differences were observed between diets C and CMC (duodenum) and also between semi-purified and cereal-based diets (duodenum and ileum). Methodological aspects for the estimation of endogenous N using the isotope dilution technique are discussed. Obviously, the digesta viscosity per se does not affect the nutrient absorption and endogenous N flow within the small intestine of pigs. Other properties of complex dietary fibre, digesta passage rate or bacterial activity probably contribute to the observed changes.     

Ileal and total tract digestibility and nitrogen utilisation in blue fox (Vulpes lagopus) fed low-protein diets supplemented with DL-methionine and L-histidine

ABSTRACT

To formulate low-protein diets for blue foxes with sufficient amounts of amino acids (AA), AA digestibility and AA requirements of the animals are crucial information. Therefore, a digestibility and nitrogen (N) balance trial was conducted with 20 blue foxes to determine the macronutrient and AA digestibility and N utilisation in low-protein diets supplemented with DL-methionine (Met) and L-histidine (His). In addition, plasma urea and plasma AA were measured. The diets were designated as P24 (control), P20, P20M, P16M and P16MH and contained energy from digestible crude protein (DCP) at 24%, 20% or 16% of total dietary metabolisable energy (ME). The 20% protein level was fed with or without Met and the 16% protein level was fed with Met and with or without His. The apparent total-tract digestibility (ATTD) of crude protein linearly decreased with decreasing dietary protein level. The ATTD of dry matter, organic matter and crude carbohydrates increased when wheat starch was added as a replacement for protein. The apparent ileal digestibility (AID) and ATTD methods were compared to determine the AA digestibility. The decreasing dietary protein supply decreased the ATTD of most of the AA: threonine, tryptophan (Trp), valine, alanine (Ala), aspartic acid (Asp), glutamic acid, glycine (Gly), proline (Pro), serine (Ser) and total AA. The AID of the AA was constant between diets. Diverging AA showed higher or lower digestibility when determined in the AID or ATTD methods. Isoleucine, lysine, Met, Ala and tyrosine showed higher levels of AID. Arginine, His, cysteine (Cys), Trp, Asp, Gly, Pro and Ser showed higher levels of ATTD, which may reflect the net loss of these AA in the large intestine. Met and His supplementation improved the ATTD and AID of the AA in question, respectively, but did not affect the other variables examined. N retention did not differ between diets and renal N excretion decreased with decreasing protein level; thus N utilisation improved. It was concluded that the protein supply and AA composition in low-protein diets with supplemented Met were adequate for adult blue foxes, since the lower protein supply improved N utilisation and did not affect N retention. However, His supplementation failed to reach the designed level and therefore showed no clear results.     

Energie-, Kohlenstoff-, Stickstoff- und Aminosäurenbilanzversuch mit wachsenden Cornish- Hähnen

The time course of AA digestion, AA balance (sV AS), and AA absorption (wV AS) was estimated on growing rats (Wistar rats, LW= 124 g) in different sections of the intestinal tract using the combination of ¹⁵N tracer and TiO₂ marker techniques. The animals received once a diet of ¹⁵N labelled wheat and yeast as protein sources supplemented by TiO₂ as a marker. Up to 6 h after feeding the amino acid composition the ¹⁵N excess and the TiO₂ content in the digesta of stomach, small and large intestine were determinated in the relation of amino acids resp. of ¹⁵N labelled amino acids to the marker. In addition the content of amino acids and the ¹⁵N excess of these amino acids were estimated in plasma. From these data the disappearance rates and the relation of exogenous to endogenous amino acids as well as the sV and the wV values of the different amino acids were calculated for the different gut sections.

The following results were obtained:

- The relative disappearance rate for N and TiO₂ marker out of the stomach went approximately parallel but with a delay for TiO₂ of about 30 minutes.

- The AA composition of the stomach content, the small and the large intestine content did not vary in dependence of the time.

- The AA composition of the stomach digesta was nearly identical to that of the diet, while that of the small intestine was between exogenous AA composition (feed) and endogenous AA composition (digesta on protein free feeding). AA composition of the large intestine digesta showed quite big differences (bacterial AA break down and AA synthesis).

- Considering a delay time (small intestine: 1 h, large intestine: 4 h) the exogenous portion of the different AA remained constant in both of these intestinal sections during the whole experimental time.

- The exogenous AA part varied for small intestine digesta between 31 and 69% (mean value: 41%), and for large intestine digesta between 13 and 39% (mean value: 22%).

- The sV AS values in the small intestine (AA balance resp. precaecal digestibility) differed from 61% (threonine) to 86% (proline) with an average of 73.4 ± 7.4%, those for wV AS (AA absorption) from 81% (lysine) to 94% (proline) with an average of 88.1±4.1%. There were significant differences between AA, but they are negligible for practical purposes.

- In the small intestine the estimated values for postprandial absorption of the exogenous AA accounted after 1 h, 2 h, 4 h and 6 h for 21%, 33.7%, 46.5%, and 70.7% of the AA intake respectively, mean absorption rate = 9.1 ± 0.5%/h.

- The AA balance in the whole tract (sV AS) was 75 to 94% (on average 82 ± 5.3%) and the wV AS (balance corrected by the ¹⁵N method) ranged from 92 to 99% (on average 96±1.8%). These values correspond to the faecal AA digestibility in conventional experiments.

- In the large intestine the postileal disappearance of the AA (sV) was on average 9.7% with a maximum value of 26% for glycine, and with a minimum for methionine of ‐2.1% caused by bacterial synthesis of methionine. Te postileal wV in the large intestine amounted to 7.5%.

- The time course of the disappearance rate of the ¹⁵N labelled AA in the small intestine and the appearance rate of these AA in the plasma showed an analogous behavior. Both of them characterize the postprandial absorption.

The following conclusion can be drawn:

The method used (combination of ¹⁵N tracer and TiO₂ marker techniques) enables determining the time course of transit and the variation of exogenous AA: endogenous AA proportion in the different intestinal sections and estimating the faecal and precaecal digestibility of the different AA.

The course of secretion and absorption of the different AA should be specified in further experiments using the more precise analysis of ¹⁵N by GC‐MS resp. GC‐C‐IRMS technique. An apply of this method to farm animals (pigs) seems to be possible.     

Changes in amino acid composition in the tissues of African catfish (Clarias gariepinus) as a consequence of dietary L-carnitine supplements

A study was undertaken to examine the effect of different amounts of dietary lysine (13 and 21 g kg^?1 diet), lipid (80 and 160 g kg^?1 diet) and L ‐carnitine (0.2 and 1.0 g kg^?1 diet) on growth performance, proximate composition and amino acid metabolism of the African catfish (Clarias gariepinus). Juvenile African catfish (23 ± 1.5 g/fish) were stocked into 70‐L aquaria (16 aquaria, 28 fish/aquarium) connected to a recirculation system during a maximum period of 74 days. All groups were fed at a level of 24 g kg^?0.8 day^?1 in an experiment run at pair feeding. Animals receiving 1.0 g carnitine accumulated up to six times more carnitine in their tissues than animals receiving 0.2 g (P < 0.05). Acyl‐carnitine and free L ‐carnitine levels increased in the whole body and in tissues. Dietary L ‐carnitine supplements increased protein‐to‐fat ratios in the body, but did not affect growth rate. Protein‐to‐fat ratios were only affected when the biosynthesis capacity of L ‐carnitine was restricted due to low lysine levels and when there was a shortage of dietary fat. When lysine was offered at 21 g kg^?1 feed, dietary L ‐carnitine supplements did not affect the amino acid concentrations of body tissues. Dietary L ‐carnitine supplements raised the concentration of glutamic acid > aspartic acid > glycine > alanine > arginine > serine > threonine in skeletal muscle tissue (P < 0.05). Total amino acid concentration in muscle and liver tissues (dry‐matter basis) increased from 506 to 564 and from 138 to 166 mg g^?1, respectively, when diets were offered with high L ‐carnitine, low lysine and low fat levels. These data suggest that dietary L ‐carnitine supplementation may increase fatty acid oxidation and possibly decrease amino acid combustion for energy.     

Metabolism of select amino acids in bacteria from the pig small intestine

This study investigated the metabolism of select amino acids (AA) in bacterial strains (Streptococcus sp., Escherichia coli and Klebsiella sp.) and mixed bacterial cultures derived from the jejunum and ileum of pigs. Cells were incubated at 37°C for 3 h in anaerobic media containing 0.5–5 mM select AA plus [U-¹⁴C]-labeled tracers to determine their decarboxylation and incorporation into bacterial protein. Results showed that all types of bacteria rapidly utilized glutamine, lysine, arginine and threonine. However, rates of the utilization of AA by pure cultures of E. coli and Klebsiella sp. were greater than those for mixed bacterial cultures or Streptococcus sp. The oxidation of lysine, threonine and arginine accounted for 10% of their utilization in these pure bacterial cultures, but values were either higher or lower in mixed bacterial cultures depending on AA, bacterial species and the gut segment (e.g., 15% for lysine in jejunal and ileal mixed bacteria; 5.5 and 0.3% for threonine in jejunal mixed bacteria and ileal mixed bacteria, respectively; and 20% for arginine in ileal mixed bacteria). Percentages of AA used for bacterial protein synthesis were 50–70% for leucine, 25% for threonine, proline and methionine, 15% for lysine and arginine and 10% for glutamine. These results indicate diverse metabolism of AA in small-intestinal bacteria in a species- and gut compartment-dependent manner. This diversity may contribute to AA homeostasis in the gut. The findings have important implications for both animal and human nutrition, as well as their health and well-beings.     

Production of l-Lysine by Leucine Auxotrophs Derived from AEC Resistant Mutant of Brevibacterium lactofermentum

The effect of amino acids was examined on the production of l-lysine by AEC resistant mutant of B. lactofermentum. Among amino acids tested, only leucine showed strong specific inhibition. In order to release the production of l-lysine from this negative effect of leucine, leucine auxotrophs were derived from AEC resistant strain of B. lactofermentum. Most of these leucine auxotrophs produced larger amount of l-lysine (maximally 41 mg/ml) than the parental strain which produced about 18 mg/ml of l-lysine. It was confirmed that leucine auxotrophs derived from AEC resistant mutant of other glutamate producing bacteria, B. saccharolyticum and Corynebacterium glutamicum. These results suggested that leucine might directly or indirectly affect the biosynthesis of lysine.

However, this increase in lysine productivity of leucine auxotrophs could not be explained by the alteration of aspartokinase (EC 2.7.2.4) and homoserine dehydrogenase (EC 1.1.1.3). These enzymes are key enzymes in lysine and threonine biosynthesis, respectively.     

Evaluation through literature data on standardized ileal digestibility and basal ileal endogenous loss of amino acids associated with barley in pigs

This meta-analysis aimed to estimate the standardized ileal digestibility (SID) and the basal ileal endogenous amino acid losses (IAA_end) in barley for growing pigs. In total, 38 different barley treatments published in 26 peer-reviewed papers were used for the meta-analysis containing information on dietary composition including amino acid (AA) contents of the assay diets, and (or) barley samples, as well as apparent ileal digestibility (AID) of AA in barley. The SID of AA was determined by either correcting AID of AA for their IAA_end or by regression analysis between the apparent ileal digestible and total dietary AA contents. The SID values obtained by correcting the AID values for their IAA_end amounted to 70%, 77%, 74% and 63% for Lys, Met, Thr and Trp, whereas those based on regression analysis method were 82%, 82%, 69% and 55%, respectively. Estimates of basal ileal endogenous loss of CP in ileal digesta varied considerably and averaged 11.84 g/kg dry matter intake (DMI), whereas IAA_end for indispensable AA ranged from 0.05 g/kg DMI for Trp to 1.90 g/kg DMI for Leu. In most cases, these estimates were considerably higher than previously reported values for IAA_end. The results of the present regression analysis indicate for most AA higher SID values compared with SID of most AA that were obtained by correcting AID values for IAA_end. In view of the observed high variations in IAA_end and the low CP content of the barley samples, estimating SID of AA based on literature data by means of the regression method may improve accuracy of SID coefficients for barley. In contrast, transformation of AID values into their corresponding SID values by using a constant correction factor for IAA_end adds an additional source of error, thereby reducing the precision in estimating SID of AA.     

Endogenous ileal losses of nitrogen and amino acids in pigs and piglets fed graded levels of casein

Abstract

In order to determine ileal losses of nitrogen (N) and amino acids (AA) and the coefficients of apparent and true ileal digestibility (AID, TID) of N and AA from casein in piglets and pigs, two experiments were conducted. In Experiment 1, 24 piglets were used. The piglets were weaned at 17 days of age, weighing 6.4 kg and cannulated at terminal ileum. Ileal digesta was collected at 28 – 29 and 35 – 36 days of age in period 1 and 2, respectively. Feed intake was 150 and 300 g · d^?1 during the first and second period. In Experiment 2, 16 castrates weighing 52.5 kg and cannulated at terminal ileum were used. The intake level of digestible energy was 2.5 times their maintenance requirement. The experiment lasted 7 days and ileal digesta was collected on day 6 – 7. Treatments consisted of four levels of N from casein: 8, 16, 24 and 32 g N · kg^?1 feed, respectively. Results showed that N level did not increase N or AA ileal losses. In piglets, N and AA ileal losses were similar between periods, except for period 2, where losses per kg DMI were about 47 and 64% higher for glycine and proline, respectively (p < 0.05). When ileal losses from pigs and piglets were compared, piglets had higher (p < 0.05) ileal losses of N and AA (excepted glutamic acid and alanine). A lower (p < 0.05) AID was observed in piglets in period 2 for N, methionine, glutamic acid, glycine and proline. With exception of glycine in pigs, all values for TID of N and AA of casein were superior to 0.90. Piglets had higher TID of N, leucine, isoleucine, valine and phenylalanine. These results showed that piglets have higher ileal losses than pigs.     

Utilization of amino acids by bacteria from the pig small intestine

This study determined the utilization of amino acids (AA) by bacteria from the lumen of the pig small intestine. Digesta samples from different segments of the small intestine were inoculated into media containing 10 mmol/L each of select AA (l-lysine, l-threonine, l-arginine, l-glutamate, l-histidine, l-leucine, l-isoleucine, l-valine, l-proline, l-methionine, l-phenylalanine or l-tryptophan) and incubated for 24 h. The previous 24-h culture served as an inoculum for a subsequent 24-h subculture during each of 30 subcultures. Results of the in vitro cultivation experiment indicated that the 24-h disappearance rates for lysine, arginine, threonine, glutamate, leucine, isoleucine, valine or histidine were 50–90% in the duodenum, jejunum or ileum groups. After 30 subcultures, the 24-h disappearance rates for lysine, threonine, arginine or glutamate remained greater than 50%. The denaturing gradient gel electrophoresis analysis showed that Streptococcus sp., Mitsuokella sp., and Megasphaera elsdenii-like bacteria were predominant in subcultures for utilizing lysine, threonine, arginine and glutamate. In contrast, Klebsiella sp. was not a major user of arginine or glutamate. Furthermore, analysis of AA composition and the incorporation of AA into polypeptides indicated that protein synthesis was a major pathway for AA metabolism in all the bacteria studied. The current work identified the possible predominant bacterial species responsible for AA metabolism in the pig small intestine. The findings provide a new framework for future studies to characterize the metabolic fate of AA in intestinal microbes and define their nutritional significance for both animals and humans.     

Effects of dietary l-lysine intake on the intestinal mucosa and expression of CAT genes in weaned piglets

The objective of this study was to evaluate effects of dietary l-lysine on the intestinal mucosa and expression of cationic amino acid transporters (CAT) in weaned piglets. Twenty-eight piglets weaned at 21 days of age (Duroc × Landrace × Yorkshire; 6.51 ± 0.65 kg body weight) were assigned randomly into one of the four groups: Zein + LYS (zein-based diet + 1.35 % supplemental lysine), Zein ? LYS (zein-based diet), NF (nitrogen-free diet), and CON (basal diet). The experiment lasted for 3 weeks, during which food intake and body weight were recorded. At the end of the trial, blood was collected from the jugular vein of all pigs, followed by their euthanasia. Dietary supplementation with lysine enhanced villus height and crypt depth in the jejunum (P < 0.05). Jejunal mRNA levels for the b^0,+-AT, y⁺LAT1 and CAT1 genes were greater (P < 0.05) in the Zein + LYS group than in the control, and the opposite was observed for CAT1. Dietary content of lysine differentially affected intestinal CAT expression to modulate absorption of lysine and other basic amino acids. Thus, transport of these nutrients is a key regulatory step in utilization of dietary protein by growing pigs and lysine in the diet influences the expression of amino acid transporters in the small intestine.     

Using the dual isotope method to assess cecal amino acid absorption of goat whey protein in rats,a pilot study

Measurement of ileal amino acids (AA) bioavailability is recommended to evaluate protein quality. A dual isotope tracer method, based on plasma isotopic enrichment ratios, has been proposed to determine true digestibility in humans. In a pilot study, we aimed to evaluate whether this method could be implemented in rats to determine AA bioavailability based on isotopic enrichment ratios measured in cecal digesta or plasma samples. Goat milk proteins were intrinsically labeled with ¹⁵N and ²H. Wistar rats were fed a meal containing the doubly labeled goat whey proteins and a tracer dose of ¹³C-spirulina. Blood samples were collected 0, 1 h and 3 h after meal ingestion from the tail vein. The rats were euthanized 4 h (n?=?6) or 6 h (n?=?6) after meal to collect plasma and intestinal contents. True orocecal protein digestibility and AA bioavailability were assessed by means of ¹⁵N and ²H enrichment in cecum content and compared with absorption indexes determined at the plasma or cecum level using isotopic ratios. Plasma kinetics of isotopic enrichment could not be completed due to the limited quantity of plasma obtained with sequential blood collection. However, the absorption indexes determined from cecal ¹⁵N or ²H/¹³C ratios gave coherent values with true orocecal AA bioavailability. This dual isotope approach with measurements of isotopic ratios in digestive content could be an interesting strategy to determine true AA bioavailability in ileal digesta of rats.

     

Endogenous ileal losses of nitrogen and amino acids in pigs and piglets fed graded levels of casein

In order to determine ileal losses of nitrogen (N) and amino acids (AA) and the coefficients of apparent and true ileal digestibility (AID, TID) of N and AA from casein in piglets and pigs, two experiments were conducted. In Experiment 1, 24 piglets were used. The piglets were weaned at 17 days of age, weighing 6.4 kg and cannulated at terminal ileum. Ileal digesta was collected at 28-29 and 35-36 days of age in period 1 and 2, respectively. Feed intake was 150 and 300 g x d(-1) during the first and second period. In Experiment 2, 16 castrates weighing 52.5 kg and cannulated at terminal ileum were used. The intake level of digestible energy was 2.5 times their maintenance requirement. The experiment lasted 7 days and ileal digesta was collected on day 6-7. Treatments consisted of four levels of N from casein: 8, 16, 24 and 32 g N x kg(-1) feed, respectively. Results showed that N level did not increase N or AA ileal losses. In piglets, N and AA ileal losses were similar between periods, except for period 2, where losses per kg DMI were about 47 and 64% higher for glycine and proline, respectively (p < 0.05). When ileal losses from pigs and piglets were compared, piglets had higher (p < 0.05) ileal losses of N and AA (excepted glutamic acid and alanine). A lower (p < 0.05) AID was observed in piglets in period 2 for N, methionine, glutamic acid, glycine and proline. With exception of glycine in pigs, all values for TID of N and AA of casein were superior to 0.90. Piglets had higher TID of N, leucine, isoleucine, valine and phenylalanine. These results showed that piglets have higher ileal losses than pigs.     

Effects of dietary protein and amino acid levels on the expression of selected cationic amino acid transporters and serum amino acid concentration in growing pigs

The absorption of lysine is facilitated by leucine, but there is no information regarding the effect of crude protein, lysine and leucine levels on the expression of cationic amino acid transporters in pigs. Therefore, an experiment was conducted with 20 pigs (14.9 +/- 0.62 kg initial body weight) to evaluate the effect of two protein levels, and the content of lysine, threonine, methionine and leucine in low crude protein diets on the expression of b(0,+) and CAT-1 mRNA in jejunum, Longissimus dorsi and Semitendinosus muscles and serum concentration of amino acids. Treatments were as follows: (i) wheat-soybean meal diet, 20% crude protein (Control); (ii) wheat diet deficient in lysine, threonine and methionine (Basal diet); (iii) Basal diet plus 0.70% L-lysine, 0.27% L-threonine, 0.10% DL-methionine (Diet LTM); (iv) Diet LTM plus 0.80% L-leucine (Diet LTM + Leu). Despite the Basal diet, all diets were formulated to meet the requirements of lysine, threonine and methionine; Diet LTM + Leu supplied 60% excess of leucine. The addition of lysine, threonine and methionine in Diet LTM increased the expression of b(0,+) in jejunum and CAT-1 in the Semitendinosus and Longissiums muscles and decreased CAT-1 in jejunum; the serum concentration of lysine was also increased (p < 0.01). Further addition of L-leucine (Diet LTM + Leu) decreased the b(0,+) expression in jejunum and CAT-1 in the Longissimus dorsi muscle (p < 0.05), increased the serum concentration ofleucine and arginine and decreased the concentration of isoleucine (p < 0.05). Pigs fed the Control diet expressed less b(0,+) in jejunum, and CAT-1 in the Semitendinosus and Longissiums muscles expressed more CAT-1 in jejunum (p < 0.05) and had lower serum concentration ofisoleucine, leucine and valine (p < 0.05), but higher lysine concentrations (p < 0.01) than those fed Diet LTM. These results indicated that both, the level and the source of dietary amino acids, affect the expression of cationic amino acid transporters in pigs fed wheat-based diets.     

Ileal endogenous losses in pigs feeding a protein-free diet or diets with different contents of casein or crystalline amino acids

The common usage of protein-free diets to estimate unspecific AA losses has been criticised as unphysiological and incorrect. Therefore, in this study different diets were tested for the determination of endogenous losses (EL) of amino acids (AA) and nitrogen (N) assuming a complete absorption in the small intestine. Seven cannulated gilts received a protein-free diet (Diet PF) or diets with 3%, 6% or 10% crude protein (CP) from crystalline AA (Diets CA) or casein (Diets CAS) according to a 7 × 7 Latin square design. After 6 d adaptation to the diet, ileal digesta was collected for 24 h and thereafter analysed for AA, N and the digestibility markers Cr₂O₃ and acid insoluble ash (AIA). Generally, among all AA, the highest amounts of EL were found for Pro, Glu and Gly, and the smallest for Met. Different levels of CP in Diets CA and CAS had no effect on EL. Significant differences between treatments were observed only for the EL of Glu, Ile, Ser (higher in Diets CA and PF), Pro and Tyr (higher in Diet PF) (p < 0.05). There were no differences in determined EL using Cr₂O₃ or AIA as digestibility markers.     

Lupinus luteus,Vicia sativa and Lathyrus cicera as protein sources for piglets: ileal and total tract apparent digestibility of amino acids and antigenic effects

Twenty-four male piglets, weaned at 28 days of age, were used to measure the total and ileal digestibility and serum immune responses to dietary leguminous seeds. The experimental diets consisted of a control starter (C) and three other diets prepared by replacing 30% of the crude protein content of the C diet by the protein of Lupinus luteus (LL), Vicia sativa (VS) or Lathyrus cicera (LC). The total tract apparent digestibility (TTAD) of energy and crude protein (CP) was lowest (P<0.001) for the LC diet. Similarly TTAD of lysine, methionine and threonine were also lowest for the LC diet. The apparent ileal digestibility (AID) of lysine, methionine and threonine were lowest for the LC diet. AID of lysine and methionine was highest for the LL seeds (0.764 and 0.834, respectively) and lowest (P<0.05) for the LC seeds (only 0.454 and 0.420, respectively). Immunoblots of individual pig serum were made to detect both residual antigenic storage proteins of the seeds of each legume used and IgGs specific to those storage proteins. Antibodies against β-conglutin of L. luteus, vicilin of V. sativa and vicilin of L. cicera were detected 28 days after feeding the diet in the sera of piglets fed on the LL, VS or LC diets, respectively. Conversely, no storage protein was found in the serum of any piglet fed either on LL, VS or LC diets. The presence of antibodies against β-conglutin of lupine, vicilin of V. sativa and vicilin of L. cicera, respectively indicated an immune response in weaned piglets. The absence of residual antigenic proteins may be due to the digestive adaptation of the piglet to the legume-based diets. However, no direct relation between the differences in digestibility coefficients among the legume seeds and their antigenicity was established.     

Apparent protein digestibility and recovery of endogenous nitrogen at the terminal ileum of pigs fed diets containing various soyabean products, peas or rapeseed hulls

Effects of the use of three different soyabean products (soya concentrate and two different soyabean meals), peas or rapeseed hulls in the diet on the apparent ileal digestibility of CP (N × 6.25) and recovery of ileal endogenous nitrogen (N) in weanling pigs were investigated. Ileal endogenous N was measured using the ¹⁵N-isotope dilution method. Thirteen castrated male pigs (BW of 12–23 kg) were fed maize starch-based diets containing either soya concentrate (SC), purified rapeseed hulls (pRH) and SC (SRH diet), soyabean meal (SBM), a mixture of toasted and untoasted soyabean meal (mSBM) or peas. The apparent ileal digestibility (AID) of dry matter (DM) for the SC, SRH, SBM, mSBM and pea diets was 82.1, 74.3, 83.3, 80.0 and 74.9% (P < 0.05), respectively. The AID of CP for these diets was 82.4, 67.6, 81.6, 68.0 and 76.9% (P < 0.05), respectively. Similar differences in the AID for amino acids (AA) in the diets were found. The AID for CP and for the sum of AA in the pRH, as calculated by the difference between the SC and SRH diet, were 26 and 41%, respectively. For the SC, SRH, SBM, mSBM and pea diet, ileal recovery (g/kg of DM intake) for endogenous N were 2.79, 3.46, 2.73, 4.89 and 3.29 (P < 0.05), respectively, and for dietary N 1.16, 4.11, 1.64, 4.15 and 2.53 (P < 0.05), respectively. For the SC, SBM and mSBM diets, differences in AID of CP and AA were associated with differences in both the ileal recovery of endogenous N and the recovery of undigested dietary N. Differences in trypsin inhibitor activity (TIA) of the soya products were likely associated with these observations. It was also concluded that fibre (Neutral Detergent Fibre; NDF) in pea could be at least in part responsible for the relatively low AID of CP and AA and the high recovery of ileal endogenous N in the pea diet. The low AID of CP and AA of pRH was likely related to the association of protein to the fibre matrix in the fibre-rich rapeseed hulls.