Effects of supplemental methionine sources in finishing pig diets on growth performance, carcass characteristics, cutting yields, and meat quality.

Supplemental methionine (Met) is widely used within the swine industry; however, data are limited regarding the effect of Met sources on carcass cutability and meat quality. The objective was to determine the effects of L-Met (LM, 99%), DL-Met (DLM, 99%), or calcium salt of DL-Met hydroxyl analog (MHA, 84%) in finishing pig diets on carcass characteristics and meat quality. At 9 weeks of age, pigs (N = 240) were allocated to 60 single-sex pens for a four-phase finishing trial that lasted 104 d. Pigs were fed a common grower diet until day 56 where pens were randomly allotted to one of the three experimental diets. For the remaining 7 wk of the finisher phase, pigs (BW = 79.9 ±â€…0.80 kg) were fed diets containing LM, DLM, or MHA, with the supplemental Met source providing 25% of standardized ileal digestible (SID) Met + cysteine (Cys) requirement based on 65% bioefficacy for MHA in comparison with LM or DLM. One pig per pen was slaughtered at the study conclusion (on day 104), and the left sides of carcasses were fabricated into subprimal cuts to determine carcass-cutting yields. Loin quality including proximate composition and shear force were measured. Hot carcass weight was not different (P = 0.34) between treatments (LM 104.5 kg; DLM 103.0 kg; MHA 101.5 kg), moreover, loin eye area was not different (P = 0.98) between treatments (LM 52.65 cm²; DLM 52.49 cm²; MHA 52.81 cm²). Boneless carcass-cutting yield was not different (P = 0.56) between treatments (LM 54.97 kg; DLM 54.82 kg; MHA 54.52 kg). Loin pH was not different (P = 0.24) between treatments (LM 5.45; DLM 5.48; MHA 5.45). However, drip loss tended to be reduced (P = 0.11) by the DLM treatment (5.58%) compared with LM (7.03%) and MHA (6.68%) treatments. Shear force was not different (P = 0.85) between treatments (LM 3.03 kg; DLM 3.06 kg; MHA 3.10 kg). However, cook loss tended to be reduced (P = 0.06) by the DLM treatment (16.20%) compared with LM (18.18%) and MHA (18.50%) treatments. These data suggest that only minimal differences in carcass cutability and meat quality can be attributed to Met source in finishing pig diets when using 65% bioefficacy for MHA relative to L-Met or DL-Met.

Effect of supplementing a Bacillus subtilis-based probiotic on performance, intestinal integrity, and serum antioxidant capacity and metabolites concentrations of heat-stressed growing pigs.

Exposing pigs to heat stress (HS) seems to modify the intestinal microbiota which may compromise the integrity of the small intestine epithelia. Probiotics, live microorganisms, can help pigs to maintain a healthy intestinal environment. Eighty pigs (21.6 ±â€…3.4 kg body weight) exposed to HS or thermal neutral (TN) conditions were used to evaluate the effect of a Bacillus subtilis-based probiotic on performance, body temperature, and intestinal integrity. Treatments were: TN pigs fed a control diet without (TN-C) or with 1 × 106 CFU probiotic/g of feed (TN-P), and HS pigs fed a control without (HS-C) or with probiotic (HS-P). The control diet was formulated with wheat, soybean meal, and free amino acids (AA). Feed and water were freely available during the 21-d study. At completion, samples from duodenum, jejunum, and ileum were collected to analyze epithelial histology and tight junction protein expression; antioxidant activity, and free AA and metabolites in serum. Relative abundance of Lactobacillus, Bifidobacterium, Escherichia coli, and Bacillus in ileal content was analyzed. Ambient temperature in the TN room ranged from 19 to 25 °C, and in HS room from 30 to 38.5 °C. Intestinal temperature in HS-P pigs was lower than in HS-C pigs. Weight gain and feed intake reduced, but feed:gain and respiration rate increased in HS compared to TN pigs, regardless of diet (P < 0.01). Probiotic increased weight gain and improved feed:gain (P < 0.05) in both TN and HS pigs, but feed intake did not differ. Heat stress decreased villi height in jejunum and villi height:crypt depth in duodenum and jejunum (P < 0.05). Probiotic increased villi height in duodenum and ileum, and villi height:crypt depth in all small intestine segments (P < 0.05). Relative abundance of Lactobacillus and Bifidobacterium tended to reduce, and E. coli tended to increase (P < 0.10) in ileal content of HS-C pigs. Ileal relative abundance of Bacillus was higher (P < 0.01) in HS-P pigs than in HS-C and TN-C pigs. Cystathionine, homocysteine, hydroxylysine, α-amino-adipic acid, citrulline, α-amino-n-butyric acid, P-Ser, and taurine were higher in HS than in TN pigs (P < 0.05). These data confirm the negative effect of HS on performance, body temperature, and intestinal integrity of pigs. These data suggest that supplementing 1 × 106 CFU probiotic/g of feed based on Bacillus subtilis DSM 32540 may help to counteract the negative effects of HS on the performance and intestinal integrity of pigs.

High ambient temperature provokes heat stress in animals, and pigs are highly affected showing low performance, and intestinal integrity and microbiota compromised. Probiotics could help pigs to maintain a healthy intestinal environment. We analyzed the effect of a probiotic based on Bacillus subtilis on growth performance, intestinal integrity of small intestine, intestinal microbiota, antioxidant activity, and serum concentration of amino acids in pigs under heat stress (HS) and thermal neutral (TN) conditions. Ambient temperature under TN and HS conditions was 19­25 and 30­38.5 °C, respectively. Weight gain and feed intake reduced in HS pigs compared to TN pigs, but probiotic increased weight gain in both TN and HS pigs. Heat stress decreased villi size in duodenum and jejunum, and probiotic restored them. Relative abundance of Lactobacillus and Bifidobacterium reduced and Escherichia coli increased in the small intestine content of HS pigs; probiotic increased the abundance of Bacillus. The activity of antioxidant enzymes increased in HS pigs fed the probiotic diet. Serum concentration of amino acid metabolites was affected by HS. These data suggest that supplementing a Bacillus subtilis-based probiotic may help to counteract the negative effects of HS on the performance and intestinal integrity of pigs.

Effects of dietary supplementation with L-arginine on the endogenous losses of amino acids in growing pigs exposed to heat stress.

Exposing pigs to heat stress (HS) provokes higher death of intestinal cells, resulting in elevated endogenous intestinal losses (EIL) of amino acids (AA) and damage to intestinal epithelia. Arginine (Arg) is precursor for the synthesis of polyamines, which are involved in proliferation of intestinal cells and restoration of the intestinal epithelia. Thus the effect of adding L-Arg to diets for HS pigs on the EIL of AA was analyzed. Twelve pigs (23.1 ± 1.1 kg body weight) implanted with T-type cannulas at the end of ileum were individually housed and allowed 15-days for surgery recovery under thermoneutral (TN) conditions (22 ± 2 °C). Following, the pigs were randomly assigned to one of three treatments: TN pigs fed a semi-purified, corn starch-3% casein basal diet (TN-B); HS pigs with the basal diet (HS-B); HS pigs consuming the basal diet supplemented with 0.20% L-Arg (HS-Arg). The experiment consisted of two 9-day periods; each period included 7-days of adaptation to their respective diet, followed by a 2-day ileal digesta collection period. Digesta was collected during 12 consecutive hours each day. The pigs were fed twice a-day. Ambient temperature (AT) inside the TN and HS rooms ranged from 18.6 to 27.6 °C and from 29.5 to 40.7 °C, respectively. Body temperature followed a pattern similar to that of AT. The daily EIL of indispensable AA increased (P < 0.01) in the HS-B pigs compared to both the TN-B and the HS-Arg pigs, however, there was no EIL difference between the TN-B and the HS-Arg pigs (P > 0.05). Likewise, with the exception of serine, daily losses of endogenous dispensable AA in the HS-B pigs were higher (P < 0.01) in comparison with those of TN-B and HS-Arg pigs. In summary, HS exposure compared to TN conditions increases the loss of endogenous AA, but dietary supplementation with L-Arg helped to counteract the negative HS effect.

Effect of dl-methionine supplementation above requirement on performance; intestinal morphology, antioxidant activity, and gene expression; and serum concentration of amino acids in heat stressed pigs.

The intestinal morphology and function can be compromised in pigs exposed to heat stress (HS), partly due to increased production of reactive-oxygen species. Because methionine (Met) functions as intracellular antioxidant, the requirement of Met may be increased in HS-pigs. The effect of dietary supplementation with dl-Met above requirement on performance, small intestine morphology, antioxidant enzymes activity, amino acid transporters expression, and serum concentration (SC) of free AA in HS-pigs was evaluated. A basal wheat-soybean meal diet was formulated to meet 100% Met requirement with the other indispensable AA exceeding at least 20% their requirement. Sixty individually housed pigs (23.0 ± 2.4 kg BW, 12 pigs per treatment) were randomly assigned to five treatments: TN100, thermal-neutral (22.7 °C) housed pigs fed the basal diet; HS100, HS120, HS140, HS160; HS-pigs (29.6 °C to 39.4 °C) fed the basal diet supplemented with dl-Met to contain 0%, 20%, 40%, and 60% dl-Met above the requirement, respectively. Pigs had free access to feed and water during the 21-d trial. Blood samples were collected on day 18 to analyze the absorptive AA-SC. The effect of ambient temperature (HS100 vs. TN100), as well as the linear and quadratic effects of increasing Met levels in the diets for HS-pigs were analyzed. The HS100 pigs gained less weight than TN100 and HS120 pigs (P < 0.01); gain:feed was also higher in HS120 pigs than in HS100 pigs (P ≤ 0.05). Feed intake of TN100 pigs was higher than that of HS-pigs fed the dl-Met supplemented diets (P < 0.05). Villi height reduced in pigs HS, but Met supplementation quadratically increased it (P < 0.05). Superoxide dismutase and catalase activities, reduced glutathione concentration, and relative expression of B0AT2 in ileum decreased (P < 0.05), but glutathione peroxidase activity increased in HS-pigs. dl-Met supplementation linearly affected catalase and glutathione peroxidase activities, as well as the relative expression of b0,+AT in jejunum (P < 0.05) of HS-pigs. The SC of Ile, Leu, Lys, Phe, and Val were higher in HS100 pigs than in TN100 pigs (P < 0.05). Graded levels of supplemental dl-Met in diets for HS-pigs linearly decreased SC of Ile, Leu, and Val (P < 0.05), tended to decrease His, Lys, and Thr (P < 0.10), and increased Met (P < 0.01). In conclusion, HS had negative effect on weight gain and intestinal morpho-physiology; however, it was ameliorated by adding 20% Met above the requirement in diets for growing pigs.

The exposure of pigs to ambient temperature above their comfort zone affects several functions of the small intestine, especially those related with digestion of feed and absorption of nutrients, which in turn reduces the availability of nutrients for growth. Amino acids such as methionine are involved in multiple functions of intestinal cells. Thus, methionine supplementation may help pigs to overcome the negative impact of their exposure to high ambient temperature. Indeed, methionine supplementation to the diet increased growth rate and feed efficiency of pigs housed under heat stress, which was presumably associated with an improvement in the utilization of the absorbed amino acids.

Changes in growth performance, plasma metabolite concentrations, and myogenic gene expression in growing pigs fed a methionine-restricted diet.

Background: Methionine (Met) is usually the second or third limiting amino acid in swine diets and plays vital roles in promoting the growth, especially, the muscle growth of pigs. This research evaluated the effects of dietary Met restriction on the growth performance, plasma metabolite concentrations, and myogenic gene expression in growing pigs. Materials and methods: Eight genes in two families (myogenic regulatory factor family and myocyte enhancer factor 2 family) were selected for the analysis. Twenty individually penned barrows (crossbred, 23.6 ± 2.4 kg) were randomly allotted to two dietary treatments (n = 10). A diet based on corn and soybean meal (Diet 1, Met-restricted) was formulated to meet or exceed the energy and nutrient requirements, except for Met. Diet 2 (Met-adequate) was formulated by adding crystalline DL-Met to Diet 1 to meet the Met requirement. During the 4-week feeding trial, average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G:F) were measured. Immediately before and after the feeding trial, blood was sampled via jugular venipuncture for plasma nutrient metabolite analysis, while Longissimus dorsi muscle were sampled via aseptic biopsy for gene expression analysis. Data were analyzed with Student t-test. Results: Pigs fed the Met-restricted diet had lower ADG and G:F (P < 0.01). Plasma Met, cysteine, and taurine concentrations were lower (P < 0.05), while glycine and histidine concentrations were higher (P < 0.05), in pigs fed the Met-restricted diet. Furthermore, the pigs fed the Met-restricted diet tended to express less myogenic factor 6 (Myf6) and myocyte enhancer factor 2D (Mef2D) mRNA in longissimus dorsi muscle (P < 0.09). Conclusion: Given the fact that Myf6, assisted by Mef2D, is involved in myocyte differentiation, this study suggests that the reduced growth performance in the Met-restricted pigs may be associated with a reduced muscle cell differentiation.

Effects of supplemental d-methionine in comparison to l-methionine on nitrogen retention, gut morphology, antioxidant status, and mRNA abundance of amino acid transporters in weanling pigs.

An N-balance experiment was conducted to test the hypothesis that d-Methionine (d-Met) has the same bioavailability and efficacy as l-Methionine (l-Met) when fed to weanling pigs. A Met-deficient basal diet containing 0.24% standardized ileal digestible (SID) Met was formulated. Six additional diets were formulated by adding 0.036%, 0.072%, or 0.108% d-Met or l-Met to the basal diet, and these diets, therefore, contained 77%, 87%, or 97% of the requirement for SID Met. Fifty-six barrows (10.53 ± 1.17 kg) were housed in metabolism crates and allotted to the seven diets with eight replicate pigs per diet. Feces and urine were collected quantitatively with 7-d adaptation and 5-d collection periods. Blood and tissue samples from pigs fed the basal diet and pigs fed diets containing 0.108% supplemental Met were collected on the last day. Results indicated that N retention (%) linearly increased (P < 0.01) as supplemental d-Met or l-Met increased in diets. Based on N retention (%) as a response, the linear slope-ratio regression estimated the bioavailability of d-Met relative to l-Met to be 101% (95% confidence interval: 57%-146%). The villus height and crypt depth in the jejunum were not affected by the Met level or Met source. Total antioxidant capacity or thiobarbituric acid reactive substance concentrations in plasma or tissue samples from pigs fed the control diet or diets containing 0.108% supplemental d-Met or l-Met were not different. Abundance of mRNA for some AA transporters analyzed in intestinal mucosa of pigs also did not differ. Therefore, it is concluded that d-Met and l-Met are equally bioavailable for weanling pigs.

Dietary Supplementation of dl-Methionine Potently Induces Sodium-Dependent l-Methionine Absorption in Porcine Jejunum Ex Vivo.

BACKGROUND: Methionine is an essential amino acid (AA) with many fundamental roles. Humans often supplement l-Met, whereas dl-Met and dl-2-hydroxy-4-(methylthio)butanoic acid (dl-HMTBA) are more frequently used to supplement livestock. OBJECTIVES: The study aimed to investigate whether dietary Met source alters the absorptive capacity for Met isomers in the small intestine of piglets. METHODS: A total of 27 male 10-wk-old piglets in 3 feeding groups received a diet supplemented with 0.21% dl-Met, 0.21% l-Met, or 0.31% dl-HMTBA to meet the Met + cystine requirement. After ≥10 d, absorptive fluxes of d-Met or l-Met were measured at a physiological concentration of 50 µM and a high concentration of 5 mM in duodenum, middle jejunum, and ileum ex vivo. Data were compared by 2-factor ANOVA. RESULTS: Across diets, fluxes of both Met isomers at both tested concentrations increased from duodenum to ileum by a factor of ∼2-5.5 (P < 0.05). Pigs supplemented with dl-Met had greater (P < 0.085) absorptive fluxes at 50 µM l-Met (0.50, 2.07, and 3.86 nmol · cm-2 · h-1) and d-Met (0.62, 1.41, and 1.19 nmol · cm-2 · h-1) than did pigs supplemented with dl-HMTBA (l-Met: 0.28, 0.76, and 1.08 nmol · cm-2 · h-1; d-Met: 0.34, 0.58, and 0.64 nmol · cm-2 · h-1) in duodenum, jejunum, and ileum, respectively. Only in jejunum of dl-Met-fed pigs, fluxes at 50 µM l-Met were reduced by the omission of luminal Na+ (from 3.27 to 0.86 nmol · cm-2 · h-1; P < 0.05) and by a cocktail of 22 luminal AAs (to 1.05 nmol · cm-2 · h-1; P < 0.05). CONCLUSIONS: Dietary supplementation of dl-Met increases the efficiency of l-Met and d-Met absorption at physiologically relevant luminal Met concentrations along the small intestine of pigs, including a very prominent induction of an Na+-dependent transport system with preference for l-Met in the mid-jejunum. Dietary supplementation with dl-Met could be a promising tool to improve the absorption of Met and other AAs.

Immune system stimulation increases the irreversible loss of cysteine to taurine, but not sulfate, in starter pigs.

An isotope tracer study was conducted to evaluate the effects of immune system stimulation (ISS) on the irreversible loss of cysteine (Cys) to taurine (Tau) and sulfate (SO4), as well as glutathione (GSH) synthesis, during the fed state in pigs. We previously have reported that ISS increases plasma Cys flux and the GSH synthesis rate at the tissue and whole-body levels in growing pigs. Thus, the current article presents the data on the irreversible loss of Cys during ISS in pigs. Ten gilts (BW: 7.0 ±â€…0.12 kg) were feed restricted a sulfur amino acids (SAA) limiting diet and injected twice with either saline (n = 4) or increasing amounts of E. coli lipopolysaccharide (n = 6). The day after the second injection, a 5-h primed continuous intravenous infusion of 35S-Cys was conducted. ISS reduced plasma Cys and total SAA concentrations (16% and 21%, respectively; P < 0.05). However, ISS had no effect on the plasma concentrations of Tau and SO4, nor did it affect the appearance of 35S in plasma Tau, plasma SO4, urinary Tau, or urinary SO4 (P > 0.19). On a whole-body basis and including urinary excretion, ISS increased the appearance of 35S in Tau by 67% (P < 0.05), but tended to decrease the appearance of 35S in SO4 by 22% (P < 0.09). Overall, the current findings indicate that during ISS, decreased plasma SAA concentrations and increased plasma Cys flux are attributed in part to increased rates of Cys conversion to Tau, but not Cys catabolism to SO4. Thus, increased utilization of Cys for the synthesis of immune system metabolites, such as GSH and Tau, is likely the main contributor to increased Cys flux during ISS in pigs. In addition, the irreversible loss of Cys during ISS is small and has a minimal impact on the daily SAA requirements of starter pigs.

Immune system stimulation increases the plasma cysteine flux and whole-body glutathione synthesis rate in starter pigs1.

Glutathione (GSH) is the major intracellular thiol that plays a role in numerous detoxification, bio-reduction, and conjugation reactions. The availability of Cys is thought to be the rate-limiting factor for the synthesis of GSH. The effects of immune system stimulation (ISS) on GSH levels and the GSH synthesis rate in various tissues, as well as the plasma flux of Cys, were measured in starter pigs fed a sulfur AA (SAA; Met + Cys) limiting diet. Ten feed-restricted gilts with initial body weight (BW) of 7.0 ± 0.12 kg were injected i.m. twice at 48-h intervals with either sterile saline (n = 4; ISS-) or increasing amounts of Escherichia coli lipopolysaccharide (n = 6; ISS+). The day after the second injection, pigs received a primed constant infusion of 35S-Cys (9,300 kBq/pig/h) for 5 h via a jugular catheter. Blood and tissue free Cys and reduced GSH were isolated and quantified as the monobromobimane derivatives by HPLC. The rate of GSH synthesis was determined by measurement of the specific radioactivity of GSH and tissue free Cys at the end of the infusion period. Plasma Cys and total SAA levels were reduced (16% and 21%, respectively), but plasma Cys flux was increased (26%) by ISS (P < 0.05). Immune system stimulation increased GSH levels in the plasma (48%; P < 0.05), but had no effect on GSH levels in the liver, small and large intestines, heart, muscle, spleen, kidney, lung, and erythrocytes. The fractional synthesis rate (FSR) of GSH was higher (P < 0.05) in the liver (34%), small intestine (78%), large intestine (72%), heart (129%), muscle (37%), and erythrocytes (47%) of ISS+ pigs compared to ISS- pigs. The FSR of GSH tended (P = 0.08) to be higher in the lungs (45%) of ISS+ pigs than in ISS- pigs. The absolute rate of GSH synthesis was increased by ISS (mmol/kg wet tissue/d ± SE, ISS- vs. ISS+; P < 0.05) in the liver (5.22 ± 0.22 vs. 7.20 ± 0.59), small intestine (2.54 ± 0.25 vs. 4.52 ± 0.56), large intestine (0.61 ± 0.06 vs. 1.06 ± 0.16), heart (0.21 ± 0.03 vs. 0.48 ± 0.08), lungs (1.50 ± 0.10 vs. 2.90 ± 0.21), and muscle (0.21 ± 0.03 vs. 0.34 ± 0.04), but it remained unchanged in erythrocytes, the kidney, and the spleen (P > 0.80). The current findings suggest that GSH synthesis is increased during ISS, contributing to enhanced maintenance sulfur amino acid requirements in starter pigs during ISS.

Effects of dietary methionine supplementation on growth performance, intestinal morphology, antioxidant capacity and immune function in intra-uterine growth-retarded suckling piglets.

This study investigated the effects of dietary supplementation with L -methionine (L -Met), DL -methionine (DL -Met) and calcium salt of the methionine hydroxyl analog (MHA-Ca) on growth performance, intestinal morphology, antioxidant capacity and immune function in intra-uterine growth-retarded (IUGR) suckling piglets. Six normal birthweight (NBW) female piglets and 24 same-sex IUGR piglets were selected at birth. Piglets were fed nutrient adequate basal diet supplemented with 0.08% L -alanine (NBW-CON), 0.08% L -alanine (IUGR-CON), 0.12% L -Met (IUGR-LM), 0.12% DL -Met (IUGR-DLM) and 0.16% MHA-Ca (IUGR-MHA-Ca) from 7 to 21 days of age respectively (n = 6). The results indicated that IUGR decreased average daily milk (dry matter) intake and average daily gain and increased feed conversion ratio of suckling piglets (p < 0.05). Compared with the NBW-CON piglets, IUGR also impaired villus morphology and reduced antioxidant capacity and immune homeostasis in the intestine of IUGR-CON piglets (p < 0.05). Supplementation with L -Met enhanced jejunal villus height (VH) and villus area and ileal VH of IUGR piglets compared with IUGR-CON piglets (p < 0.05). Similarly, DL -Met supplementation increased VH and the ratio of VH to crypt depth in the jejunum compared with IUGR-CON pigs (p < 0.05). Supplementation with L -Met and DL -Met (0.12%) tended to increase reduced glutathione content and reduced glutathione: oxidized glutathione ratio and decrease protein carbonyl concentration in the jejunum of piglets when compared with the IUGR-CON group (p < 0.10). However, supplementation with MHA-Ca had no effect on the intestinal redox status of IUGR piglets (p > 0.10). In conclusion, supplementation with either L -Met or DL -Met has a beneficial effect on the intestinal morphology and antioxidant capacity of IUGR suckling piglets.

Substitution of Dietary Sulfur Amino Acids by DL-2-hydroxy-4-Methylthiobutyric Acid Increases Remethylation and Decreases Transsulfuration in Weaned Piglets.

BACKGROUND: DL-2-hydroxy-4-methylthiobutyric acid (DL-HMTBA), an L-methionine (L-Met) hydroxyl analogue, has been suggested to be a dietary L-Met source. How dietary DL-HMTBA compared with L-Met affects whole-body L-Met kinetics in growing individuals is unknown. OBJECTIVES: We determined to what extent DL-HMTBA supplementation of an L-Met-deficient diet affects whole-body L-Met and L-cysteine (L-Cys) kinetics, protein synthesis (PS), and the L-Met incorporation rate in liver protein (L-MetInc) compared with L-Met and DL-Met supplementation in a piglet model. METHODS: Forty-five, 28-d-old weaned piglets (male, German Landrace) were allocated to 4 dietary groups: L-Met-deficient diet [Control: 69% of recommended L-Met plus L-Cys supply; 0.22% standardized ileal digestible (SID) L-Met; 0.27% SID L-Cys; n = 12] and Control diet supplemented equimolarly to 100% of recommended intake with either L-Met (n = 12; LMET), DL-Met (n = 11; DLMET), or DL-HMTBA (n = 10; DLHMTBA). At 47 d of age, the piglets were infused with L-[1-13C; methyl-2H3]-Met and [3,3-2H2]-Cys to determine the kinetics and PS rates. Plasma amino acid (AA) concentrations, hepatic mRNA abundances of L-Met cycle and transsulfuration (TS) enzymes, and L-MetInc were measured. RESULTS: During feed deprivation, L-Met kinetics did not differ between groups, and were ≤3 times higher in the fed state (P < 0.01). Remethylation (RM) was 31% and 45% higher in DLHMTBA than in DLMET and Control pigs, respectively, and the RM:transmethylation (TM) ratio was 50% higher in DLHMTBA than in LMET (P < 0.05). Furthermore, TS and the TS:TM ratio were 32% lower in DLHMTBA than in LMET (P < 0.05). L-MetInc was 42% lower in DLMET and DLHMTBA than in L-Met-deficient Control pigs, whereas plasma AA and hepatic mRNA abundances were similar among DL-HMTBA-, L-Met-, and DL-Met-supplemented pigs. CONCLUSIONS: In piglets, DL-HMTBA compared with L-Met and DL-Met supplementation increases RM and reduces the TS rate to conserve L-Met, but all 3 Met isomers support growth at a comparable rate.

Impact of immune system stimulation on the ileal nutrient digestibility and utilisation of methionine plus cysteine intake for whole-body protein deposition in growing pigs.

The impact of immune system stimulation (ISS) on the ileal nutrient digestibility and utilisation of dietary methionine plus cysteine (SAA) intake for whole-body protein deposition (PD) was evaluated in growing pigs. For this purpose, sixty barrows were used in two experiments: thirty-six pigs in Expt I and twenty-four pigs in Expt II. Pigs were feed restricted and assigned to five levels of dietary SAA allowance (three and two levels in Expt I and II, respectively) from SAA-limiting diets. Following adaptation, pigs at each dietary SAA level were injected with either increasing amounts of Escherichia coli lipopolysaccharide (ISS+; eight and six pigs per dietary SAA level in Expt I and II, respectively) or saline (ISS - ; four and six pigs in Expt I and II, respectively) while measuring the whole-body nitrogen (N) balance. After N-balance observations, pigs were euthanised, organs were removed and ileal digesta were collected for determining nutrient digestibility. Ileal digestibility of gross energy, crude protein and amino acids was not affected by ISS (P>0·20). ISS reduced PD at all levels of dietary SAA intake (P< 0·01). The linear relationship between daily dietary SAA intake and PD observed at the three lowest dietary SAA intake levels indicated that ISS increased extrapolated maintenance SAA requirements (P< 0·05), but had no effect on the partial efficiency of the utilisation of dietary SAA intake for PD (P>0·20). Physiological and metabolic changes associated with systemic ISS had no effect on the ileal digestibility of nutrients per se, but altered SAA requirements for PD in growing pigs.