Requirement of standardized ileal digestible valine to lysine ratio for 8- to 14-kg pigs

Dietary supplementation with tryptophan increases the plasma concentrations of tryptophan, kynurenine, and melatonin in Yili mares

Context Tryptophan (Trp) is the precursor of melatonin (MT) and the latter plays vital physiological roles in mares. Aims The purpose of this experiment was to investigate the effects of dietary Trp supplementation on the plasma Trp, kynurenine (Kyn), 5-hydroxytryptophan (5-HT), and melatonin (MT) concentrations in female Yili horses. Methods Twenty Yili mares aged 2 years with mean bodyweight (BW) of 263.5 ± 14.77 kg and of similar stature were selected and randomly allocated to the control (CON; basal diet), basal diet plus Trp at 20 mg/kg BW (TRP1), basal diet plus Trp at 40 mg/kg BW (TRP2), or basal diet plus Trp at 60 mg/kg BW (TRP3) group. Key results The plasma total Trp, Kyn, and MT concentrations in all Trp groups steadily increased, reached their peak values, and gradually decreased after Trp supplementation between 0 h and 12 h. However, the plasma 5-HT concentration displayed the opposite trend. Peak plasma total Trp and 5-HT concentrations were attained between 1 h and 3 h, while those of KYN and MT appeared between 4 h and 6 h after Trp supplementation. The plasma total Trp and Kyn concentrations were significantly higher in TRP2 and TRP3 than in CON between 1 h and 12 h (P < 0.05) after Trp supplementation. The plasma 5-HT concentration was significantly (P < 0.05) lower in TRP1 than in CON at 3 h, 4 h, 6 h, 9 h, and 12 h after Trp supplementation. The plasma MT concentrations in TRP1 and TRP2 were significantly (P < 0.05) higher than in CON at 3 h, 4 h, and 12 h, and at 0 h, 1 h, and 12 h after Trp supplementation (P < 0.05). Conclusions Dietary Trp supplementation can increase the plasma total Trp, Kyn, and MT concentrations in Yili mares and the optimal Trp dosage was 20 mg/kg BW. Implication The addition of Trp to a basal diet or feed may increase the plasma total Trp, Kyn, and MT concentrations in female horses.

The biological functions and metabolic pathways of valine in swine

Valine is an essential amino acid and a type of branched-chain amino acid. Due to the involvement of branched-chain amino acids in various metabolic pathways, there has been a surge of interests in valine nutrition and its role in animal physiology. In pigs, the interactions between valine and other branched-chain amino acids or aromatic amino acids are complex. In this review, we delve into the interaction mechanism, metabolic pathways, and biological functions of valine. Appropriate valine supplementation not only enhances growth and reproductive performances, but also modulates gut microbiota and immune functions. Based on past observations and interpretations, we provide recommended feed levels of valine for weaned piglets, growing pigs, gilts, lactating sows, barrows and entire males. The summarized valine nutrient requirements for pigs at different stages offer valuable insights for future research and practical applications in animal husbandry.

The Linear-Logistic Model: A Novel Paradigm for Estimating Dietary Amino Acid Requirements

This study aimed to determine whether current methods for estimating AA requirements for animal health and welfare are sufficient. An exploratory data analysis (EDA) was conducted, which involved a review of assumptions underlying AA requirements research, a data mining approach to identify animal responses to dietary AA levels exceeding those for maximum protein retention, and a literature review to assess the physiological relevance of the linear-logistic model developed through the data mining approach. The results showed that AA dietary levels above those for maximum growth resulted in improvements in key physiological responses, and the linear-logistic model depicted the AA level at which growth and protein retention rates were maximized, along with key metabolic functions related to milk yield, litter size, immune response, intestinal permeability, and plasma AA concentrations. The results suggest that current methods based solely on growth and protein retention measurements are insufficient for optimizing key physiological responses associated with health, survival, and reproduction. The linear-logistic model could be used to estimate AA doses that optimize these responses and, potentially, survival rates.

Impact of increasing standardized ileal digestible valine: lysine in diets containing 30% dried distiller grains with solubles on growing pig performance

A total of 2,430 pigs (DNA 600 × Topigs Norsvin 70, initially 39.4 kg) were used in a 28-d trial to determine the standardized ileal digestible (SID) Val:Lys requirement for pigs fed with diets containing 30% DDGS. Treatments included five diets containing 30% DDGS with SID Val:Lys ratios of 60%, 65%, 70%, 75%, and 80%, plus a corn soybean meal (SBM) diet, for a total of six dietary treatments. Diets were formulated to be isocaloric through the inclusion of fat and to contain equal amounts of SID Lys within phase. Pens were assigned to dietary treatment in a randomized complete block design with initial body weight (BW) as the random blocking factor. Each dietary treatment was replicated 15 times and pens contained 27 pigs, balanced for sex. Increasing the SID Val:Lys ratio in diets containing 30% DDGS increased (Quadratic; P ≤ 0.007) 14-d BW, final BW, average daily gain (ADG), average daily feed intake (ADFI), and gain:feed (G:F) for all periods. Providing an SID Val:Lys ratio of 75% resulted in the heaviest 14-d BW and final BW as well as greater ADG and ADFI of pigs fed with 30% DDGS for all periods. The G:F response was maximized when an SID Val:Lys ratio of 70% was provided from day 0 to 14 while an SID Val:Lys ratio of 75% maximized G:F from day 14 to 28 and for the cumulative period. The SID Val:Lys requirement was estimated at 66.6% (95% CI [65.9, 67.4]), 65.7 (95% CI: [64.8, 66.5]), and 68.4% (95% CI [66.0, 70.8]) for ADG, ADFI, and G:F, respectively, using the straight broken line (SBL) method and 69.9% (95% CI [68.2, 71.5]), 67.6 (95% CI [65.4, 69.8]), and 72.8% (95% CI [69.8, 75.8]) for the quadratic broken line (QBL) method. Pigs fed the corn-SBM diet had heavier 14-d BW, final BW, and greater ADG, ADFI, G:F (P ≤ 0.032) compared to pigs fed diets containing 30% DDGS, except for cumulative ADFI compared to pigs receiving 75% SID Val:Lys (P = 0.167). In conclusion, these results suggest that when feeding 30% DDGS during the growing period, an SID Val:Lys ratio of 68% would yield more than 99% and 97% of the maximum ADG and G:F response for the 39 to 68 kg pigs. However, growth performance of pigs fed diets containing 30% DDGS did not equate to pigs consuming the corn-SBM diet regardless of the SID Val:Lys ratio.

The Optimal Valine to Lysine Ratio for Performance Parameters in Weaned Piglets

Simple Summary

Animal production has an impact on environmental issues, like global warming. Reducing the protein level in animal feed has the potential to decrease fecal and urinary nitrogen excretion and consequently reduces the environmental nitrogen load. The usage of crystalline L-valine is a potential solution to maintain growth performance of piglets when feeding low protein diets. Aim of this study was to determine the optimal valine requirement in weaned piglets. Therefore, 200 weaned piglets were allotted to five feeding groups and received diets with consecutive increasing amounts of L-valine. The supplementation of L-valine to a valine-deficient basal diet led to an increase in growth and feed intake of weaned piglets. Supplementary valine has the potential to decrease the amount of excess dietary nitrogen, namely through meeting valine requirements via supplementary valine instead of increasing dietary crude protein content.

Abstract

The optimal digestible (d) Valine (Val) to d Lysine (Lys) ratio (dVal:dLys) in weaned piglets was determined using two different regression models. A total of 200 piglets were allotted to five feeding groups and fed a corn-soybean meal based basal diet supplemented with consecutive increasing amounts of crystalline L-valine in order to reach dVal:dLys of 0.59, 0.63, 0.67, 0.71, 0.75 in the pre-starter (0–13 days) and 0.57, 0.62, 0.66, 0.70, 0.75 in the starter phase (13–43 days). In the starter phase and during the whole period, supplementing the basal diet with L-valine resulted in an improvement in body weight gain and feed intake. An exponential asymptotic (EA) and a curvilinear-plateau (CLP) regression model were fit to feed intake and body weight gain data. The estimated dVal:dLys for body weight gain was found to be 0.68 (EA, 95% of maximum response) and 0.67 (CLP) in the starter phase and 0.65 (EA, 95% of maximum response and CLP) in the total trial period. It is concluded that the supplementation of a valine-deficient basal diet for weaned piglets with L-valine improves the piglet’s weight gain and feed intake and that a dVal:dLys of 0.68 is recommended to optimize body weight gain.

Net Absorption and Metabolism of β-Hydroxy- β-Methyl Butyrate during Late Gestation in a Pig Model

The leucine metabolite, β-hydroxy-β-methyl butyrate (HMB), is widely used in human nutrition and animal production as a nutritional supplement. Although the HMB usage during late gestation has been demonstrated to have a positive effect on fetal development, knowledge on net absorption and metabolism of HMB and impact of HMB on branched chain amino acids (BCAAs) metabolism is lacking. To address this, we conducted a study using pigs during the perinatal period as a model organism. Eight-second parity sows were fitted with indwelling catheters in the femoral artery and in the portal, hepatic, femoral, and mesenteric veins. Eight hourly sets of blood samples were taken starting 30 min before the morning meal on day –10 and day –3 relative to parturition. Four control (CON) sows were fed a standard lactation diet from day –15 and throughout the experiment, and 4 HMB sows were fed the control diet supplemented with 15 mg Ca(HMB)₂/kg body weight mixed in one third of the morning meal from day –10 until parturition. Blood gases, plasma metabolites, milk compositions, and apparent total tract digestibility of nutrients were measured. Arterial plasma concentrations of HMB (p < 0.001), Cys (p < 0.001), and Lys (p < 0.10) were increased in HMB supplemented sows, while arterial plasma triglycerides concentration was decreased (p < 0.05). The net portal recovery of Ala and Asp were increased in HMB sows (p < 0.05). Sows fed HMB had increased hepatic vein flow and net hepatic fluxes of Met, Asn, and Gln (p < 0.05). In contrast, the femoral extraction rates of Ala and Ser were decreased by dietary HMB supplementation (p < 0.05). Dietary HMB treatment and sampling time relative to feeding had an interaction on arterial concentrations, net portal fluxes, and femoral extraction rates of BCAAs. The net portal recovery of HMB was 88%, while 14% of supplemented HMB was excreted through urine and 4% through feces. Moreover, the gastrointestinal tract metabolized 8% while the liver metabolized 12%. Finally, 26% of the daily intake of HMB was secreted via colostrum at the day of farrowing. This study demonstrated that dietary HMB supplementation increased net uptake of amino acids and increased fatty acid oxidation through improving blood flow and insulin sensitivity during the late gestation. Most importantly, oral HMB administration could maintain a stable postprandial absorption and altered metabolism in BCAAs. Net portal flux of HMB at 5.5 to 6.5 h after feeding approached zero, indicating that HMB ideally should be administrated two or three times, daily.

Excess dietary leucine in diets for growing pigs reduces growth performance, biological value of protein, protein retention, and serotonin synthesis1

An experiment was conducted to test the hypothesis that excess dietary Leu affects metabolism of branched-chain amino acids (BCAA) in growing pigs. Forty barrows (initial body weight [BW]: 30.0 ± 2.7 kg) were housed individually in metabolism crates and allotted to 5 dietary treatments (8 replicates per treatment) in a randomized complete block design. The 5 diets were based on identical quantities of corn, soybean meal, wheat, and barley and designed to contain 100%, 150%, 200%, 250%, or 300% of the requirement for standardized ileal digestible Leu. Initial and final (day 15) BW of pigs were recorded. Daily feed consumption was also recorded. Urine and fecal samples were collected for 5 d following 7 d of adaptation to the diets. At the end of the experiment, blood and tissue samples were collected to analyze plasma urea N (PUN), plasma and hypothalamic serotonin, tissue BCAA, serum and tissue branched-chain α-keto acids, and messenger ribonucleic acid abundance of genes involved in BCAA metabolism. Results indicated that acid detergent fiber, average daily feed intake, and gain-to-feed ratio decreased (linear, P < 0.05) as dietary Leu increased. A trend (linear, P = 0.082) for decreased N retention and decreased (linear, P < 0.05) biological value of dietary protein was also observed, and PUN increased (linear, P < 0.05) as dietary Leu increased. A quadratic reduction (P < 0.05) in plasma serotonin and a linear reduction (P < 0.05) in hypothalamic serotonin were observed with increasing dietary Leu. Concentrations of BCAA in liver increased (linear, P < 0.001), whereas concentrations of BCAA in skeletal muscle decreased (linear, P < 0.05) as dietary Leu increased. Concentration of α-ketoisovalerate was reduced (linear and quadratic, P < 0.001) in liver, skeletal muscle, and serum, and α-keto-β-methylvalerate was reduced (linear, P < 0.001; quadratic, P < 0.001) in skeletal muscle and serum. In contrast, α-keto isocaproate increased (linear, P < 0.05) in liver and skeletal muscle and also in serum (linear and quadratic, P < 0.001) with increasing dietary Leu. Expression of mitochondrial BCAA transaminase and of the E1α subunit of branched-chain α-keto acid dehydrogenase increased (linear, P < 0.05) in skeletal muscle as dietary Leu increased. In conclusion, excess dietary Leu impaired growth performance and nitrogen retention, which is likely a result of increased catabolism of Ile and Val, which in turn reduces availability of these amino acids resulting in reduced protein retention, and excess dietary Leu also reduced hypothalamic serotonin synthesis.

Valine and isoleucine supplementation improve performance and serum biochemical concentrations in growing gilts fed low-protein diets

This study evaluated the effects of valine and isoleucine supplementation in low-crude-protein (CP) diets on performance, serum parameters, and carcass traits in growing gilts. Two-hundred gilts (29.1 ± 1.7 kg) were allotted randomly to one of five diets that included a control CP (177 g kg−1) or four low-CP (135 g kg−1) diets for 45 d. The low-CP diets were added with lysine + threonine + methionine (LCM), LCM+ tryptophan (LCT), LCT + valine (LCV), or LCV + isoleucine (LCI), respectively. Non significant difference in average daily gain was obtained in gilts receiving the control, LCV, or LCI diets, which was higher than that of pigs fed the LCM or LCT diets (P < 0.05). The supplementation of crystalline tryptophan, valine, and isoleucine improved the average daily feed intake and serum levels of total protein, tryptophan, and isoleucine (linear and quadratic effects, P < 0.05) and serum valine concentration (linear effect, P < 0.05). The results indicated that the valine supplementation, or the both combination of valine and isoleucine, could further improve the performance in 29–62 kg gilts fed the 135 g kg−1 CP diet.

Branched-chain amino acid interactions in growing pig diets

The branched-chain amino acids (BCAA) Leu, Ile, and Val share the first steps of their catabolism due to similarities in their structure. The BCAA are reversibly transaminated in skeletal muscle through the activity of branched-chain aminotransferase and then transported to the liver. They undergo an irreversible decarboxylation catalyzed by the branched-chain α-keto acid dehydrogenase complex. Both enzymes are common to Leu, Ile, and Val and increased enzymatic activity stimulated by an excess of one of them will increase the catabolism of all BCAA, which can result in antagonisms. Leucine and its keto acid are the most potent stimulators of BCAA catabolic enzymes. Moreover, BCAA and large neutral amino acids (LNAA) share common brain transporters. Research has shown that high concentrations of BCAA, especially Leu, can decrease the absorption of LNAA, such as Trp, which is a precursor of serotonin and can have a significant impact in feed intake regulation. Finally, high Leu concentrations have the ability to overstimulate the mTOR signaling pathway, resulting in an inhibitory effect on feed intake. Most of the research conducted to evaluate the impact of BCAA on growth performance of pigs seems to agree that high levels of Leu decrease weight gain, mostly due to a reduction in feed intake. However, some studies, mostly with finishing pigs, observed no evidence for an impact on growth performance even with extremely high levels of Leu. It could be hypothesized that these inconsistencies are driven by the entire dietary amino acid profile as opposed to only considering the level of Leu. Grow-finish diets typically contain high levels of Leu, but the other BCAA are also well above the requirement and could potentially mitigate the negative impact of Leu on BCAA catabolism. Indeed, some studies suggest that when diets contain high levels of Leu, more Ile and Val are needed to optimize growth performance. However, the precise relationship between BCAA and their balance in swine diets is not fully understood. More research is needed to understand and quantify the relationship between LNAA and BCAA.

Standardized ileal digestible valine:lysine dose response effects in 25- to 45-kg pigs under commercial conditions

Two experiments were conducted to estimate the standardized ileal digestible valine:lysine (SID Val:Lys) dose response effects in 25- to 45-kg pigs under commercial conditions. In experiment 1, a total of 1,134 gilts (PIC 337 × 1050), initially 31.2 kg ± 2.0 kg body weight (BW; mean ± SD) were used in a 19-d growth trial with 27 pigs per pen and seven pens per treatment. In experiment 2, a total of 2,100 gilts (PIC 327 × 1050), initially 25.4 ± 1.9 kg BW were used in a 22-d growth trial with 25 pigs per pen and 12 pens per treatment. Treatments were blocked by initial BW in a randomized complete block design. In experiment 1, there were a total of six dietary treatments with SID Val at 59.0, 62.5, 65.9, 69.6, 73.0, and 75.5% of Lys and for experiment 2 there were a total of seven dietary treatments with SID Val at 57.0, 60.6, 63.9, 67.5, 71.1, 74.4, and 78.0% of Lys. Experimental diets were formulated to ensure that Lys was the second limiting amino acid throughout the experiments. Initially, linear mixed models were fitted to data from each experiment. Then, data from the two experiments were combined to estimate dose-responses using a broken-line linear ascending (BLL) model, broken-line quadratic ascending (BLQ) model, or quadratic polynomial (QP). Model fit was compared using Bayesian information criterion (BIC). In experiment 1, ADG increased linearly (P = 0.009) with increasing SID Val:Lys with no apparent significant impact on G:F. In experiment 2, ADG and ADFI increased in a quadratic manner (P < 0.002) with increasing SID Val:Lys whereas G:F increased linearly (P < 0.001). Overall, the best-fitting model for ADG was a QP, whereby the maximum mean ADG was estimated at a 73.0% (95% CI: [69.5, >78.0%]) SID Val:Lys. For G:F, the overall best-fitting model was a QP with maximum estimated mean G:F at 69.0% (95% CI: [64.0, >78.0]) SID Val:Lys ratio. However, 99% of the maximum mean performance for ADG and G:F were achieved at, 68% and 63% SID Val:Lys ratio, respectively. Therefore, the SID Val:Lys requirement ranged from73.0% for maximum ADG to 63.2% SID Val:Lys to achieve 99% of maximum G:F in 25- to 45-kg BW pigs.

Modeling the effects of standardized ileal digestible valine to lysine ratio on growth performance of nursery pigs. Transl Anim Sci 2017;1:448-457. [PMID: 32704668 PMCID: PMC7204984 DOI: 10.2527/tas2017.0049]

Two experiments evaluated the effects of increasing Lys and Val on growth performance of nursery pigs. In Exp. 1,300 nursery pigs (PIC 327 × 1,050, initially 6.7 ± 1.4 kg BW) were randomly allotted to 1 of 6 diets containing 1.10, 1.20, 1.30, 1.40, 1.50, or 1.60% standardized ileal digestible (SID) Lys, with 10 pens per dietary treatment and 5 pigs per pen. Linear and nonlinear mixed models were fitted to estimate dose responses. From d 0 to 14, and for the overall 28 d period, ADG and G:F increased (linear, P < 0.001) as SID Lys increased, with no evidence of differences in ADFI. Dose response modeling indicated the SID Lys requirement for ADG and G:F was at 1.45% using a broken line linear (BLL) and greater than 1.60% using a quadratic polynomial (QP) model. In Exp. 2, 280 nursery pigs (PIC 327 × 1,050, initially 6.5 ± 1.3 kg BW) were allotted to 1 of 7 diets containing SID Val:Lys ratios of 50, 57, 63, 68, 73, 78, or 85%. The dietary SID Lys concentration 1.24% SID Lys which was below the estimated requirement from Exp. 1 and ensured the Val:Lys ratio was not underestimated. From d 0 to 14, ADG, ADFI, and G:F increased (quadratic, P < 0.039) with increasing SID Val:Lys. For ADG, the best fitting model was a BLL, with a breakpoint estimate of 62.9% SID Val:Lys [52.2, 73.7] ratio while for G:F the best fit model was a quadratic polynomial with a maximum G:F at 71.7% SID Val:Lys (95%CI:[58, > 85]). Average daily feed intake was also modeled with a quadratic polynomial and maximized at 73.7% Val:Lys (95% CI: [61, > 85]). In conclusion, the Val requirement ranged from approximately 63 to 74% of Lys depending on the response criteria modeled.

Effects of dietary valine:lysine ratio on the performance, amino acid composition of tissues and mRNA expression of genes involved in branched-chain amino acid metabolism of weaned piglets

Objective

The goal of this study was to investigate the effects of dietary standard ileal digestible (SID) valine:lysine ratios on performance, intestinal morphology, amino acids of liver and muscle, plasma indices and mRNA expression of branched-chain amino acid (BCAA) metabolism enzymes.

Methods

A total of 144 crossbred pigs (Duroc×Landrace×Large White) weaned at 28±4 days of age (8.79±0.02 kg body weight) were randomly allotted to 1 of 4 diets formulated to provide SID valine:lysine ratios of 50%, 60%, 70%, or 80%. Each diet was fed to 6 pens of pigs with 6 pigs per pen (3 gilts and 3 barrows) for 28 days.

Results

Average daily gain increased quadratically (p<0.05), the villous height of the duodenum, jejunum and ileum increased linearly (p<0.05) as the SID valine:lysine ratio increased. The concentrations of plasma α-keto isovaleric and valine increased linearly (p<0.05), plasma aspartate, asparagine and cysteine decreased (p<0.05) as the SID valine:lysine ratio increased. An increase in SID lysine:valine levels increased mRNA expression levels of mitochondrial BCAA transaminase and branched-chain α-keto acid dehydrogenase in the longissimus dorsi muscle (p<0.05).

Conclusion

Using a quadratic model, a SID valine:lysine ratio of 68% was shown to maximize the growth of weaned pigs which is slightly higher than the level recommended by the National Research Council [6].

Nontargeted LC-MS Metabolomics Approach for Metabolic Profiling of Plasma and Urine from Pigs Fed Branched Chain Amino Acids for Maximum Growth Performance

The metabolic response in plasma and urine of pigs when feeding an optimum level of branched chain amino acids (BCAAs) for best growth performance is unknown. The objective of the current study was to identify the metabolic phenotype associated with the BCAAs intake level that could be linked to the animal growth performance. Three dose-response studies were carried out to collect blood and urine samples from pigs fed increasing levels of Ile, Val, or Leu followed by a nontargeted LC-MS approach to characterize the metabolic profile of biofluids when dietary BCAAs are optimum for animal growth. Results showed that concentrations of plasma hypoxanthine and tyrosine (Tyr) were higher while concentrations of glycocholic acid, tauroursodeoxycholic acid, and taurocholic acid were lower when the dietary Ile was optimum. Plasma 3-methyl-2-oxovaleric acid and creatine were lower when dietary Leu was optimum. The optimum dietary Leu resulted in increased urinary excretion of ascorbic acid and choline and relatively decreased excretion of 2-aminoadipic acid, acetyl-dl-valine, Ile, 2-methylbutyrylglycine, and Tyr. In conclusion, plasma glycocholic acid and taurocholic acid were discriminating metabolites to the optimum dietary Ile. The optimum dietary Leu was associated with reduced plasma creatine and urinary 2-aminoadipic acid and elevated urinary excretion of ascorbic acid and choline. The optimum dietary Val had a less pronounced metabolic response reflected in plasma or urine than other BCAA.

Evaluation of in situ valine production by Bacillus subtilis in young pigs

Mutants of Bacillus subtilis can be developed to overproduce Val in vitro. It was hypothesized that addition of Bacillus subtilis mutants to pig diets can be a strategy to supply the animal with Val. The objective was to investigate the effect of Bacillus subtilis mutants on growth performance and blood amino acid (AA) concentrations when fed to piglets. Experiment 1 included 18 pigs (15.0±1.1 kg) fed one of three diets containing either 0.63 or 0.69 standardized ileal digestible (SID) Val : Lys, or 0.63 SID Val : Lys supplemented with a Bacillus subtilis mutant (mutant 1). Blood samples were obtained 0.5 h before feeding and at 1, 2, 3, 4, 5 and 6 h after feeding and analyzed for AAs. In Experiment 2, 80 piglets (9.1±1.1 kg) were fed one of four diets containing 0.63 or 0.67 SID Val : Lys, or 0.63 SID Val : Lys supplemented with another Bacillus subtilis mutant (mutant 2) or its parent wild type. Average daily feed intake, daily weight gain and feed conversion ratio were measured on days 7, 14 and 21. On day 17, blood samples were taken and analyzed for AAs. On days 24 to 26, six pigs from each dietary treatment were fitted with a permanent jugular vein catheter, and blood samples were taken for AA analysis 0.5 h before feeding and at 1, 2, 3, 4, 5 and 6 h after feeding. In experiment 1, Bacillus subtilis mutant 1 tended (P<0.10) to increase the plasma levels of Val at 2 and 3 h post-feeding, but this was not confirmed in Experiment 2. In Experiment 2, Bacillus subtilis mutant 2 and the wild type did not result in a growth performance different from the negative and positive controls. In conclusion, results obtained with the mutant strains of Bacillus subtilis were not better than results obtained with the wild-type strain, and for both strains, the results were not different than the negative control.