Digestible Tryptophan Research Articles

Effects of autolysis and hydrolysis of bacterial protein meal grown on natural gas on chemical characterization and amino acid digestibility

Bacterial protein meal produced from bacteria cultured on natural gas is a novel alternative protein source. Several products with different nutritional features were made from basic bacterial protein meal (BBP) by autolysis and hydrolysis. These products were investigated in terms of chemical characterization of the protein fraction and amino acid digestibility, using mink as model animal. The BBP, autolysate, autolysate extract, hydrolysate extract, and the insoluble byproducts of the latter two exhibited considerable differences in amino acid profile and great differences in protein solubility and molecular size. Apparent digestibility of arginine, lysine and methionine was high in all products, while cysteine digestibility was low. Compared to BBP, the extracts of autolysate and hydrolysate showed higher digestibility of most amino acids. All products of autolysis showed higher tryptophan digestibility but lower cysteine digestibility compared to BBP. The byproducts from autolysate and hydrolysate with low protein solubility and large molecule size had lower amino acid digestibility than the extracts. Autolysis and hydrolysis and separation into extracts of high protein solubility and small molecular size increased amino acid digestibility of the bacterial protein.

Evaluation of low-oligosaccharide, low-phytate whole soybeans and soybean meal in canine foods1

Eight mature dogs (19.3 +/- 0.1 kg) were used in an experiment to compare the effects of feeding soybeans containing low concentrations of oligosaccharides and phytate on nutrient availability in complete foods fed to dogs. All foods were formulated to be isonitrogenous and contained low-oligosaccharide, low-phytate soybean meal (LLM); conventional soybean meal (SBM); low-oligosaccharide, low-phytate whole soybeans (LLB); or conventional whole soybeans (WSB) as the protein source. Daily DMI averaged 287 +/- 4 g/d. Fecal outputs were greatest for LLB and WSB, averaging 48.2 g DM/d. Small intestinal DM digestibility ranged from 80.9% (LLM) to 74.0% (LLB) but was unaffected by treatment. Large intestinal DM digestibility did not differ among treatments (P = 0.652). Total-tract DM digestibility was higher (P = 0.020) for LLM (87.0%) than for SBM (84.8%). No difference in total-tract DM digestibility was observed for the two WSB foods (average = 83.3%; P = 0.286). Nitrogen retention did not differ among foods containing LLM and SBM (1.2 g of N/d; P = 0.486) or LLB and WSB (0.9 g of N/d; P = 0.225). Small intestinal N digestibility did not differ among LLM- and SBM-containing foods (80.6%; P = 0.190) or LLB and WSB (69.3%; P = 0.640). Total-tract N digestibility did not differ among foods containing LLM and SBM (83.5%; P = 0.627) or LLB and WSB (76.8%; P = 0.968). Tryptophan digestibility was higher for SBM than for LLM (P = 0.039). Histidine and tryptophan digestibilities were higher in WSB compared with LLB (P = 0.049 and P < 0.001, respectively). No differences in nonessential AA digestibility were observed when comparing soy-based foods. The results of this study demonstrate that LLM, SBM, LLB, and WSB can be effective sources of protein for canine foods and have a high digestibility. Differences in small intestinal digestibility of tryptophan and histidine may require consideration when formulating diets using low-oligosaccharide, low-phytate soybeans or meal.

Tryptophan requirement of growing pigs at various body weights.

The purpose of this study was to determine the tryptophan (Trp) requirement of growing pigs at different body weight (BW) ranges. Three performance experiments were conducted with female pigs in the BW ranges of 25-50, 50-80 and 80-115 kg. In addition to the performance experiments, nitrogen balance experiments were carried out in which pigs weighing 56, 66 and 86 kg were used. Trp-deficient basal diets were formulated to which varying amounts of l-Trp were added. The amino acid concentrations of the diets were analysed; concentrations of standardized digestible amino acids were calculated on the basis of tabular values. The calculated concentrations of standardized ileal digestible tryptophan were 0.81, 1.11, 1.41, 1.71, 2.01 g/kg diet in the lower BW range (25-50 kg), 0.71, 0.96, 1.21, 1.46, 1.71 g/kg diet in the middle BW range (50-80 kg), and 0.49, 0.69, 0.89, 1.09, 1.29 g/kg diet in the upper BW range (80-115 kg). Dose-response relationships were evaluated by means of an exponential regression model. In all three age ranges, performance parameters as well as nitrogen retention were strongly influenced by the dietary concentration of standardized ileal digestible tryptophan. According to the exponential model, in the 25-50 kg BW range, 95% of the maximum feed consumption, BW gain and nitrogen retention were achieved at concentrations between 1.96 and 2.00 g of standardized ileal digestible Trp per kilogram diet, corresponding to 3.32-3.39 g/day. In the BW range of 50-80 kg, 95% of the maximum of these parameters occurred at concentrations of standardized ileal digestible tryptophan in excess of the highest concentration of 1.71 g/kg diet, corresponding to 3.71 g/day. In the BW range of 80-115 kg, 95% of the maximum of BW gain and nitrogen retention were recorded at concentrations of 1.22 and 0.84 g standardized ileal digestible Trp per kilogram diet, corresponding to 3.77 and 2.25 g/day, respectively. Related to the energy value of the diets, the optimal concentration of standardized ileal digestible tryptophan are between 140 and 143 mg/MJ metabolizable energy (ME) in the BW range of 25-50 kg, in excess of 127 mg/MJ ME in the BW range of 50-80 kg and between 62 and 90 mg/MJ ME in the BW range of 80-115 kg. In conclusion, it is suggested that the requirement of standardized ileal digestible tryptophan for growing pigs might be higher than currently assumed.

Evaluation of apparent ileal digestibility of amino acids in chinese corn by-products for growing-finishing pigs

Twelve crossbred barrows (BW 47 ± 2.81 kg) were fitted with a T-cannula in the terminal ileum and fed one of ten diets containing corn gluten meal, dried distillers grain or dried distillers grain with solubles as the sole protein source, according to a 6 × 6 Latin Square design. Lysine, tryptophan and methionine were, the first, second and third limiting amino acids in these by-products. The ileal apparent digestibility of methionine, tyrosine, leucine and phenylalanine in corn gluten meal was high. The ileal apparent digestibility of tryptophan, tyrosine and leucine differed significantly in corn gluten meal. The ileal apparent digestibility of amino acids was higher in dried distillers grain with solubles than in dried distillers grain. To predict the ileal apparent digestibility of tryptophan, methionine and threonine linear regression equations were derived. The results suggested that processing technique can influence the ileal apparent digestibility of amino acids in corn by-products. It was concluded that the direct technique cannot accurately determine the ileal apparent digestibility of tryptophan in dried distillers grain with solubles and dried distillers grain, due to its low content. The content of an amino acid in a feedstuff used as the sole source of protein must meet the minimum requirement of pigs when the ileal apparent digestibility of constituent amino acids is determined using the direct technique.

Studies on the tryptophan requirement of piglets

Three experiments were conducted to determine the requirement of tryptophan for piglets. In the first two experiments dose‐response relationships between the dietary tryptophan concentration and performance criteria of piglets were examined in order to determine the dietary tryptophan concentration required for maximum performance. In the first experiment dietary tryptophan levels ranged from 1.09 to 2.32 g per kg, in the second experiment they ranged from 1.70 to 2.60 g per kg. In both experiments a close correlation was observed between the dietary tryptophan concentration and piglet performance criteria (feed intake, daily gains, feed efficiency). In the first experiment, regression analysis using a non‐linear model revealed that the optima, defined as 95% of the asymptotic response in the model used, for feed intake and daily gains were achieved at tryptophan levels in excess of the highest concentration of 2.32 g per kg feed. The performance level of the piglets in this experiment was generally very low, however. In the second experiment feed intake, the optimum tryptophan concentration, defined as 95% of the asymptotic response, for daily gains and feed efficiency were achieved within a small range between 2.07 and 2.14 g tryptophan per kg feed, corresponding to 1.84 to 1.91 g precaecal digestible tryptophan per kg feed or 0.153 to 0.159 g tryptophan per MJ ME. These results suggest that the tryptophan concentration for maximum performance of piglets is probably higher than has been implied in numerous studies to date. The third experiment was set up to investigate the effect of the reduced feed intake and the effect of an inadequate tryptophan supply per se on the animals’ growth. Here a two‐factorial experimental design was used also by varying the energy density of the diet (13 vs. 14MJ ME per kg feed). In addition to tryptophan deficient groups (1.5 g tryptophan per kg feed), this experiment contained conventional control groups (2.6 g tryptophan per kg feed, ad libitum feeding) and pair‐fed control groups (2.6 g tryptophan per kg feed, feed intake identical to that of the tryptophan deficient group). The energy density had no significant effect on the animals’ performance and increasing the energy density of the diet did not significantly affect feed and energy intake or daily gains of the tryptophan deficient animals. Feed intake, daily gains and feed efficiency of the fryptophan deficient groups were markedly poorer (by 30, 35 and 10%) than in the ad libitum control groups. When compared with the pair‐fed control groups, on the other hand, the performance of the tryptophan deficient groups in terms of daily gains, feed conversion and energy efficiency was only slightly and not significant lower by 1, 4 and 3%, respectively. These results demonstrate conclusively that the growth depression in tryptophan deficiency is almost entirely due to the marked reduction in feed intake rather than to a direct limitation of protein accretion caused by an inadequate tryptophan supply.

Exigência de triptofano para frangos de corte de 1 a 21 dias de idade

Com o objetivo de determinar as exigências nutricionais em triptofano para frangos de corte machos e fêmeas, durante a fase inicial, foram utilizados 800 pintos machos e fêmeas, no período de 1 a 21 dias de idade, com peso médio inicial de 44,7 e 44,6 g, respectivamente. As aves receberam uma dieta basal deficiente em triptofano (0,180%). O delineamento experimental utilizado foi em blocos casualizados em arranjo fatorial 5 x 2 (tratamento x sexo), com quatro repetições por sexo e 20 aves/unidade experimental. Os tratamentos consistiram da suplementação da dieta basal com cinco níveis de triptofano (0; 0,015; 0,030; 0,045; e 0,060%). Foi avaliado o desempenho das aves, sendo os valores de exigências em triptofano estimados por meio dos modelos de regressão polinomial e LRP. Foi considerado o coeficiente de digestibilidade verdadeira do triptofano da dieta basal de 90,33%. As suplementações com L-triptofano influenciaram o ganho de peso dos machos, porém, não houve efeito sobre a conversão alimentar, sugerindo recomendação mínima de 0,212 e 0,195% de triptofano total e digestível, respectivamente. Entretanto, para as fêmeas, as suplementações com L-triptofano influenciaram o ganho de peso e a conversão alimentar, sugerindo recomendação mínima de 0,208 e 0,191% de triptofano total e digestível, respectivamente.

Variability of apparent ileal amino acid digestibility in different pea samples for growing-finishing pigs

Six barrows, average initial body weight 32.5 kg, fitted with a simple T-can-nula at the distal ileum, were used to investigate factors responsible for the variability of apparent ileal amino acid (AA) digestibility values among six pea samples. The barrows were fed six corn-starch-based diets, formulated to contain 16.5% crude protein (CP) (as-fed) from six different pea samples, according to a 6 × 6 Latin square design. Chromic oxide (0.3%) was used as the digestibility marker. The pigs were fed twice daily, at 0800 and 2000 h. The dietary allowance was 1600 g−1. Each experimental period lasted 7 d. Ileal digesta were collected at 2-h intervals for a total of 24 h from 0800 h on day 6 to 0800 h on day 8. With the exception of arginine, cysteine, histidine, and methionine, there were differences (P &lt; 0.05) in the apparent ileal digestibility values of the indispensable including semi-essential (+semi-) AA among the pea samples. Of the indispensable AA (+semi-) within each pea sample, the digestibility values of arginine and lysine were relatively high, ranging from 88.3 to 91.3% and from 78.7 to 85.2%, respectively, while the digestibility values of cysteine, methionine, and tryptophan were relatively low, ranging from 53.8 to 62.7%, from 69.4 to 75.4%, and from 53.1 to 70.4%, respectively. With the exception of arginine, cysteine, and tryptophan, the ileal digestibility values of the indispensable AA (+semi-) were negatively correlated (P &lt; 0.05) with the neu-tral-detergent fiber content in the pea samples. Of all the AA, only the digestibility of tryptophan was negatively correlated (P &lt; 0.05) with the trypsin inhibitor activity in the pea samples. The significant finding of this study was that with the exception of arginine, cysteine, and proline, differences in the digestibility values of all other AA in the pea samples were positively correlated (P &lt; 0.05) with their respective dietary AA contents. This suggests that differences in AA levels in the assay diets were responsible for the variability of apparent ileal digestibility values of AA between pea samples. Therefore, to eliminate this methodological effect, true rather than apparent ileal AA digestibility values for peas should be determined. Key words: Amino acids, ileal digestibility, peas, pigs

The influence of cecectomy on metabolizable energy and amino acid digestibility of select feedstuffs for white Pekin ducks

Twenty-four cecectomized and 24 intact White Pekin ducks were used in two experiments to assess the influence of cecectomy on ME and amino acid digestibility of several feed ingredients for ducks. Corn and soybean meal (SBM) were evaluated in Experiment 1, and bakery meal (BM), red dog (RD), and wheat middlings (WM) were evaluated in Experiment 2. Nitrogen-corrected true metabolizable energy and amino acid digestibility of the ingredients were assayed concurrently. In Experiment 1, TME of corn was higher (P < or = 0.05) in cecectomized ducks, and intact ducks demonstrated greater (P < or = 0.05) ability to utilize the energy in SBM. Intact ducks exhibited higher (P < or = 0.05) true digestibilities of lysine and methionine. True digestibility of tryptophan was higher (P < or = 0.05) for cecectomized ducks. True digestibility of indispensable amino acids in SBM did not differ (P > or = 0.05) between cecectomized and intact ducks. In Experiment 2, cecectomized ducks exhibited greater (P < or = 0.05) ability to utilize the energy in RD. Intact ducks exhibited greater (P < or = 0.05) ability to utilize the energy in WM. True digestibility of indispensable amino acids in BM, RD, and WM was variable. Results of the present study suggest that the effect of cecectomy on nutrient digestibility in ducks is dependent on the feedstuff assayed.

Requirement of young pigs for apparent ileal digestible tryptophan

In 5 growth trials with a total of 420 pigs, tryptophan requirements from 20 to 40 kg liveweight were estimated. L-Tryptophan 0, 0.15, 0.30, 0.45 and 0.60 g/kg was added to a basal diet containing tapioca, barley and maize, with CP 162 g/kg and tryptophan 1.65 g/kg. The control diet was supplemented with lysine, methionine plus cystine, threonine, isoleucine, valine and histidine to assure that only tryptophan was limiting pig performance. Diets were freely given as pellets. Total tryptophan was about 2.10 g/kg for optimal weight gain and feed conversion efficiency in a diet containing NE 9.5 MJ/kg, corresponding with apparent ileally digestible tryptophan 1.77 g/kg.

Digestible tryptophan requirements of starting, growing, and finishing pigs.

Seven hundred eight crossbred pigs were used in growth and digestion trials to determine the digestible tryptophan (Trp) requirement of starting (6 to 16 kg), growing (22 to 50 kg), and finishing (55 to 97 kg) pigs. Each growth trial evaluated a corn-fish meal-corn gluten meal basal diet, the basal diet with five incremental additions of L-Trp, and a control corn-soybean meal diet. The tryptophan content of the six incremental diets ranged from .13 to .255% for starting pigs, .08 to .18% for growing pigs, and .063 to .163% for finishing pigs. Lysine contents of basal diets were 1.38, .90, and .72% for starting, growing, and finishing diets, respectively. In all trials, ADG, ADFI, and gain/feed increased (P less than .001) linearly and quadratically as dietary Trp increased. Broken-line regression analyses determined the total dietary Trp requirements needed to optimize performance to be .19, .13, and .09% (as-fed basis) for starting, growing, and finishing pigs, respectively. These concentrations equated to Trp intakes of .96, 2.18, and 2.88 g/d. A digestion trial using growing pigs (29 kg initially) determined the apparent ileal digestibility of Trp in the basal starting and growing diets to be 72 and 70%, respectively; a similar trial with finishing pigs (55 kg initially) found 59% Trp digestibility for the basal finishing diet. Mean digestibility of L-Trp was 97%. Based on these values and the total Trp requirements given above, the digestible Trp requirements are .15, .10, and .06% for starting, growing, and finishing pigs, respectively.