J. K. Htoo

Amino acid digestibility in heated soybean meal fed to growing pigs

Heat treatment of soybean meal (SBM) is necessary to reduce the concentration of trypsin inhibitors, but excessive heat treatment may reduce AA concentration and digestibility because AA can be destroyed by the Maillard reaction. The objective of this experiment was to determine the effects of heat treatment of SBM on apparent ileal digestibility and standardized ileal digestibility (SID) of AA by growing pigs. A source of conventional dehulled SBM (48.5% CP) was divided into 4 batches. One batch was not additionally heated, 1 batch was autoclaved at 125°C for 15 min, 1 batch was autoclaved at 125°C for 30 min, and 1 batch was oven-dried at 125°C for 30 min. Four SBM-cornstarch diets were formulated, and each of the 4 batches of SBM was used as the sole source of dietary AA in 1 diet. A N-free diet was used to estimate basal endogenous losses of AA. Ten growing barrows with an initial BW of 25.3 ± 2.0 kg were individually fitted with a T-cannula in the distal ileum. Pigs were allotted to treatments in a replicated 5 × 5 balanced Latin square design with 5 diets and 5 periods. Each period lasted 7 d, and ileal digesta were collected on d 6 and 7 of each period. Results of the experiment indicated that the apparent ileal digestibility and SID of CP and all AA decreased linearly (P < 0.01) as the time of autoclaving increased from 0 to 30 min. The concentration of furosine and the color of samples of SBM indicated that autoclaving resulted in a Maillard reaction in the SBM. However, oven drying at 125°C for 30 min did not change (P > 0.10) the SID of CP and AA in the SBM or the furosine concentration, and the color in the oven-dried sample indicated that this sample was not heat damaged. In conclusion, the digestibility of all AA in autoclaved SBM is linearly reduced as the autoclaving time increases from 0 to 30 min. The reason for these changes is most likely that autoclaving at 125°C results in Maillard reactions in SBM.

Fermentable Fiber Ameliorates Fermentable Protein-Induced Changes in Microbial Ecology, but Not the Mucosal Response, in the Colon of Piglets

Dietary inclusion of fermentable carbohydrates (fCHO) is reported to reduce large intestinal formation of putatively toxic metabolites derived from fermentable proteins (fCP). However, the influence of diets high in fCP concentration on epithelial response and interaction with fCHO is still unclear. Thirty-two weaned piglets were fed 4 diets in a 2 × 2 factorial design with low fCP/low fCHO [14.5% crude protein (CP)/14.5% total dietary fiber (TDF)]; low fCP/high fCHO (14.8% CP/16.6% TDF); high fCP low fCHO (19.8% CP/14.5% TDF); and high fCP/high fCHO (20.1% CP/18.0% TDF) as dietary treatments. After 21-23 d, pigs were killed and colon digesta and tissue samples analyzed for indices of microbial ecology, tissue expression of genes for cell turnover, cytokines, mucus genes (MUC), and oxidative stress indices. Pig performance was unaffected by diet. fCP increased (P < 0.05) cell counts of clostridia in the Clostridium leptum group and total short and branched chain fatty acids, ammonia, putrescine, histamine, and spermidine concentrations, whereas high fCHO increased (P < 0.05) cell counts of clostridia in the C. leptum and C. coccoides groups, shifted the acetate to propionate ratio toward acetate (P < 0.05), and reduced ammonia and putrescine (P < 0.05). High dietary fCP increased (P < 0.05) expression of PCNA, IL1β, IL10, TGFβ, MUC1, MUC2, and MUC20, irrespective of fCHO concentration. The ratio of glutathione:glutathione disulfide was reduced (P < 0.05) by fCP and the expression of glutathione transferase was reduced by fCHO (P < 0.05). In conclusion, fermentable fiber ameliorates fermentable protein-induced changes in most measures of luminal microbial ecology but not the mucosal response in the large intestine of pigs.

Immune system stimulation reduces the efficiency of tryptophan utilization for body protein deposition in growing pigs

The effect of immune system stimulation (ISS) on N retention and Trp utilization in pigs fed Trp-limiting diets was evaluated using 36 growing pigs (20.0 ± 1.1 kg BW; 3 blocks of 12 barrows). Pigs were randomly assigned to 1 of 5 diets (Diet 1, 2, 4, and 5, n = 7; Diet 3, n = 8) and fed restrictively at 800 g/d. Diets 1 to 4 were generated by blending Diet 1 with a protein-free supplement and were calculated to contain varying amounts of standardized ileal digestible (SID) Trp (1.31, 1.05, 0.80, and 0.55 g/kg). To confirm that Trp was the first-limiting AA in Diets 1 to 4, an additional diet was used (Diet 5), which was equivalent to Diet 4 and contained 0.34 g/kg of added Trp. After a 5-d adaptation period, pigs were injected every 2 d with increasing amounts of E. coli lipopolysaccharide to induce ISS (initial dose 20 μg/kg BW, increasing 15% each subsequent injection). Whole body N balance was measured in 3 periods: before immune stimulation (pre-ISS) and during ISS in 2 subsequent periods (ISS-1, 3 d; ISS-2, 4 d). Regression analysis was used to estimate the marginal efficiency of Trp utilization for whole body protein deposition (PD; N retention × 6.25). Plasma concentrations of acute-phase proteins and white blood cell counts increased (P < 0.001) and plasma albumin decreased (P < 0.001) during ISS. Nitrogen retention increased (P < 0.001) as Trp intake increased. Nitrogen retention was numerically greater but not statistically different between Diet 5 (added Trp diet) and Diet 4. Whole body N retention was less (P < 0.05) during ISS due primarily to an increase (P < 0.05) in urinary N excretion. There was a linear response (P < 0.05) in N retention, urinary N, and total excreted N to increasing Trp intake. Protein deposition increased by 88.2 ± 5.2, 82.5 ± 5.1, and 92.5 ± 3.4 g/d for each additional g/d of SID Trp intake during pre-ISS, ISS-1, and ISS-2, respectively, but the intercept was not different (-32.3 g/d). The slope of the response of PD to increasing Trp intake (based on the common intercept) was less during ISS-1 compared with pre-ISS (P = 0.01) or ISS-2 (P = 0.002) but not different between pre-ISS and ISS-2. Immune system stimulation reduced N retention in pigs fed limiting dietary Trp. The efficiency of Trp utilization for protein deposition was also reduced during ISS, indicating that the Trp requirement for PD is increased ∼7% during an inflammatory state.

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 b0,+ 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 b0,+ 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 b0,+ expression in jejunum and CAT-1 in the Longissimus dorsi muscle (p < 0.05), increased the serum concentration of leucine and arginine and decreased the concentration of isoleucine (p < 0.05). Pigs fed the Control diet expressed less b0,+ 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 of isoleucine, 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.

Effect of processing of rapeseed under defined conditions in a pilot plant on chemical composition and standardized ileal amino acid digestibility in rapeseed meal for pigs.

Five rapeseed meals (RSM) were produced from a single batch of rapeseed in a large-scale pilot plant under standardized conditions. The objective was to evaluate the effect of residence time in the desolventizer/toaster (DT) on chemical composition and standardized ileal digestibility (SID) of AA in RSM. Four RSM, with 48, 64, 76, and 93 min residence time and using unsaturated steam in the DT, referred to as RSM48, RSM64, RSM76, and RSM93, respectively, and 1 low-glucosinolate RSM, which was subjected to sequential treatment with unsaturated steam, saturated steam, and dry heat in the DT, referred to as low-GSL RSM, were assayed. Six barrows (average initial BW = 22 ± 1 kg) were surgically fitted with a T-cannula at the distal ileum. Pigs were allotted to a 5 × 6 row × column design with 5 diets and 5 periods. The 5 RSM were included in a cornstarch-casein-based basal diet. In addition, basal ileal endogenous losses and SID of AA originating from casein were determined at the conclusion of the experiment in 2 additional periods by means of the regression method and using 3 graded levels of casein. The SID of AA in the 5 RSM was determined in difference to SID of AA originating from casein. The glucosinolates (GSL) were efficiently reduced, whereas NDF, ADF, ADL, and NDIN contents increased and reactive Lys (rLys) and Lys:CP ratio decreased as the residence time in the DT was increased from 48 to 93 min. The SID of most AA in RSM linearly decreased (P < 0.05) as the residence time in the DT increased from 48 to 93 min. Moreover, there was a linear decrease (P < 0.05) in SID of AA with increasing NDF, ADF, ADL, and NDIN contents in these RSM, whereas SID of AA linearly decreased (P < 0.05) with decreasing levels of GSL and rLys and a decreasing Lys:CP ratio. The decrease (P < 0.05) in SID of AA amounted from 3 up to 6 (percentage units) for most AA, except for SID of Cys and Lys, which decreased by 10 and 11%-units (P < 0.05), respectively, as the residence time in the DT was increased from 48 to 93 min. The SID in low-GSL RSM was for CP and most AA similar to RSM93 but lower ( < 0.05) compared to RSM48. It can be concluded that time and energy-intensive heat treatment results in lower contents of SID AA in RSM together with a reduction in GSL levels. The feed industry would most likely benefit from a rapid and accurate prediction of SID of AA, for example, based on content of NDIN, GSL, rLys or on Lys:CP ratio, in different batches of RSM used for feed manufacturing.

Immune system stimulation increases the optimal dietary methionine to methionine plus cysteine ratio in growing pigs

Chronic subclinical levels of disease occur frequently in intensive swine production and compromise nutrient use efficiency. Feeding additional Met plus Cys (M+C) has been implicated in improving the response of the animal to immune system stimulation (ISS) because they can serve as substrates for generating compounds involved in the immune response, such as glutathione and acute phase proteins. A N-balance study was conducted to assess the optimal dietary Met to Met plus Cys ratio (M:M+C) during ISS in 20-kg pigs. Thirty-six pigs were fed 800 g/d of 1 of 5 M+C-limiting diets, containing graded levels of M:M+C (0.42, 0.47, 0.52, 0.57, and 0.62) and supplying 2.5 g/d of M+C. After adaptation, N balances were determined sequentially during a 5-d prechallenge period and 2 ISS periods of 3 and 4 d, respectively. To induce ISS, pigs were injected intramuscularly with repeated and increasing doses of Escherichia coli lipopolysaccharide. Eye temperature and blood profile confirmed effective ISS. During ISS period 1, ISS reduced the mean N balance more severely than ISS period 2 (8.7 ± 0.3 vs. 9.6 ± 0.4 g/d; P < 0.001) and was less than the prechallenge period (10.0 ± 0.2 g/d; P < 0.001). An interactive effect of ISS and diet on N balance was observed (P < 0.001). Based on quadratic-plateau regression analysis, the optimal dietary M:M+C was 0.57 ± 0.03 and 0.59 ± 0.02 for the prechallenge period and ISS period 2, respectively. The optimal dietary M:M+C for ISS period 1 was found to be greater than 0.62, indicating that the optimal M:M+C is greater during ISS. It is suggested that this is the result of preferential use of Met during ISS. In conclusion, ISS results in an increase in the optimal dietary M:M+C in growing pigs.

Low-protein amino acid-supplemented diets for growing pigs: effect on expression of amino acid transporters, serum concentration, performance, and carcass composition.

Pigs fed protein-bound AA appear to have a higher abundance of AA transporters for their absorption in the jejunum compared with the duodenum. However, there is limited data about the effect of dietary free AA, readily available in the duodenum, on the duodenal abundance of AA transporters and its impact on pig performance. Forty-eight pigs (24.3 kg initial BW) distributed in 4 treatments were used to evaluate the effect of the CP level and form (free vs. protein bound) in which AA are added to diets on the expression of AA transporters in the 3 small intestine segments, serum concentration of AA, and performance. Dietary treatments based on wheat and soybean meal (SBM) were 1) low-CP (14%) diet supplemented with L-Lys, L-Thr, DL-Met, L-Leu, L-Ile, L-Val, L-His, L-Trp, and L-Phe (LPAA); 2) as in the LPAA but with added L-Gly as a N source (LPAA+N); 3) intermediate CP content (16%) supplemented with L-Lys HCl, L-Thr, and DL-Met (MPAA); and 4) high-CP (22%) diet (HP) without free AA. At the end of the experiment, 8 pigs from LPAA and HP were sacrificed to collect intestinal mucosa and blood samples and to dissect the carcasses. There were no differences in ADG, ADFI, G:F, and weights of carcass components and some visceral organs between treatments. Weights of the large intestine and kidney were higher in HP pigs (P < 0.01). Expression of b(0,+) in the duodenum was higher in pigs fed the LPAA compared with the HP diet (P= 0.036) but there was no difference in the jejunum and ileum. In the ileum, y+ L expression tended to be higher in pigs fed the LPAA diet (P = 0.098). Expression of b(0,+) in LPAA pigs did not differ between the duodenum and the jejunum, but in HP pigs, the expression of all AA transporters was higher in the jejunum than in the duodenum or ileum (P < 0.05). The serum concentration of Arg, His, Ile, Leu, Phe, and Val was higher but serum Lys and Met were lower in pigs fed the HP diet (P < 0.05). These results indicate that LPAA can substitute up to 8 percentage units of protein in HP wheat-SBM diets without affecting pig performance; nonessential N does not seem to be limiting in very low-protein wheat-SBM diets for growing pigs. Also, the inclusion of free AA in the diet appears to affect their serum concentration and the expression of the AA transporter b0,+ in the duodenum of pigs.

Standardized ileal digestibility of amino acids in eight genotypes of soft winter wheat fed to growing pigs.

A study with growing pigs was conducted to determine the chemical composition and standardized ileal digestibility (SID) of CP and AA of 8 wheat genotypes that have recently been added to the German Descriptive Variety List. These genotypes included Tabasco, KWS Erasmus, Tobak, Skalmeje, Mulan, Event, Tommi, and Adler. The 8 genotypes were grown under identical environmental conditions on the same site, and they were harvested and processed under the same conditions. Nine barrows with an initial BW of 32 ± 2 kg were surgically fitted with simple ileal T-cannulas and allotted to a row-column design with 9 pigs and 8 periods of 6 d each. Wheat was the sole dietary source of CP and AA. Among the 8 wheat genotypes, contents of CP ranged from 10.9 to 13.3% (as-fed basis), whereas contents of total nonstarch polysaccharides ranged from 8.0 to 9.4% (as-fed basis). The SID of CP in the 8 genotypes ranged from 83 to 87%, with greatest ( = 0.01) values for Event and lowest ( = 0.01) for all other wheat genotypes. Intermediate SID of CP values were obtained for Adler and KWS Erasmus. For Lys, greater ( < 0.05) SID was observed in Adler (73%) and KWS Erasmus (74%) in comparison to Tommi, Tobak, and Mulan (69%). Adler had greater SID of Met (88%; = 0.01) when compared to Tabasco (86%); Tobak, Skalmeje, and Mulan (85%); and Tommi (84%). Among the 8 wheat genotypes, standardized ileal digestible content (cSID) of CP followed total CP content and ranged from 9.1 to 11.3% (as-fed basis). Standardized ileal digestible content of both CP and AA were greater ( < 0.001) in Adler compared to all other genotypes. For most AA, Tabasco had the lowest ( < 0.001; except for His, Trp, Asp, and Cys) cSID values of all wheat genotypes. The cSID of CP decreased ( < 0.001) as the starch content in the 8 wheat genotypes increased, but cSID of CP increased ( < 0.001) as the CP content in the 8 genotypes increased. Because SID and cSID of CP and most AA increased ( < 0.05) with lower test weight and falling number, these variables may aid to predict SID and cSID in wheat batches, whereas other nutrients such as fiber fractions are not suitable due to low variation among the 8 genotypes. The present study provides a comprehensive database on nutritional composition and SID of CP and AA of 8 wheat genotypes grown under identical conditions. Because the SID values in these genotypes are lower when compared to literature data, digestibility values in actual feed tables for wheat may overestimate their protein values and need to be updated.

Nitrogen Absorbed from the Large Intestine Increases Whole-Body Nitrogen Retention in Pigs Fed a Diet Deficient in Dispensable Amino Acid Nitrogen

BACKGROUND Nitrogen absorption from the large intestine is considered of limited value for supporting body protein synthesis in animals and humans, but it may be of benefit when the dietary supply of nitrogen for synthesis of dispensable amino acids (DAAs) is deficient. OBJECTIVE A whole-body nitrogen balance study was conducted to evaluate the impact of nitrogen absorption from the large intestine of pigs fed a diet deficient in DAA nitrogen. METHODS Nine cecally cannulated barrows were fed a cornstarch and casein-based diet with a high indispensable amino acid (IAA) nitrogen to total nitrogen ratio (IAA:TN; 0.75). Pigs were randomly assigned to saline or 1 of 2 urea nitrogen infusion rates into the cecum (low and high, 1.5 and 3.0 g/d, respectively) following a 3 × 3 Latin square design. At the high urea nitrogen infusion rate, IAA:TN was 0.55. At slaughter, liver samples were taken to measure activity of carbamoyl phosphate synthetase I (CPS-I), glutamate dehydrogenase (GDH), and Gln synthetase (Gln-S). RESULTS Whole-body nitrogen retention improved with urea infusion (4.86 ± 0.20 g/d, 6.40 ± 0.21 g/d, and 7.75 ± 0.19 g/d for saline and low and high infusion rates, respectively; P < 0.05), as well as body weight gain. The marginal efficiency of using nitrogen absorbed from the large intestine for improving nitrogen retention was not affected by urea nitrogen infusion rate (P > 0.10). Enzyme activity of CPS-I or Gln-S was not different between treatments (P > 0.10), but GDH showed a trend for a positive linear response with increasing urea nitrogen infusion rate (P = 0.06). CONCLUSION These results indicate that urea nitrogen absorbed from the large intestine is efficiently used for increasing body protein deposition when feeding pigs a diet deficient in DAA nitrogen.

Influence of fermentable carbohydrates or protein on large intestinal and urinary metabolomic profiles in piglets

It was recently shown that variations in the ratio of dietary fermentable carbohydrates (fCHO) and fermentable protein (fCP) differentially affect large intestinal microbial ecology and the mucosal response. Here we investigated the use of mass spectrometry to profile changes in metabolite composition in colon and urine associated with variation in dietary fCHO and fCP composition and mucosal physiology. Thirty-two weaned piglets were fed 4 diets in a 2 × 2 factorial design with low fCP and low fCHO, low fCP and high fCHO, high fCP and low fCHO, and high fCP and high fCHO. After 21 to 23 d, all pigs were euthanized and colon digesta and urine metabolite profiles were obtained by mass spectrometry. Analysis of mass spectra by partial least squares approach indicated a clustering of both colonic and urinary profiles for each pig by feeding group. Metabolite identification and annotation using the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways revealed increased abundance of metabolites associated with arachidonic acid metabolism in colon of pigs fed a high concentration of fCP irrespective of dietary fCHO. Urinary metabolites did not show as clear patterns. Mass spectrometry can effectively differentiate metabolite profiles in colon contents and urine associated with changes in dietary composition. Whether metabolite profiling is an effective tool to identify specific metabolites (biomarkers) or metabolite profiles associated with gut function and integrity needs further elucidation.