Interactions of various supplies of isoleucine, valine, leucine and tryptophan on the performance of laying hens.

The present study was undertaken to investigate the interactions among the supplies of isoleucine, leucine, valine, and tryptophan in laying hens. A three-factor trial was conducted with laying hens in which the dietary concentrations of isoleucine (5.7, 8.0, and 11.5 g/kg), valine and leucine (6.3 and 7.2 g/kg and 10.1 and 11.5 g/kg, respectively), and tryptophan (1.5 and 2.4 g/kg) were varied. At the lowest concentration of valine + leucine, an increase in dietary isoleucine concentration led to a dose-dependent reduction in feed consumption, daily egg mass, and body weight gain and an increase of the isoleucine concentration in plasma. At a high dietary concentration of valine + leucine, excess dietary isoleucine concentration caused only a weak depression of performance parameters; the isoleucine concentration in plasma was independent of the dietary isoleucine concentration. Increasing the dietary tryptophan concentration did not influence the effect of an excessive dietary isoleucine concentration on performance parameters. Increasing the tryptophan concentration from 1.5 to 2.4 g/kg diet did, however, lead to a significant increase in feed consumption, irrespective of the supply of isoleucine, valine, and leucine. In conclusion, our study demonstrates that the supply of valine + leucine influenced the effects of excess dietary isoleucine in laying hens, whereas the supply with tryptophan did not.

Studies on requirement and excess of isoleucine in laying hens.

Three production trials and one nitrogen balance trial were conducted with Lohmann Brown hens to determine the requirement for and effects of an excess of isoleucine in layers at different ages (24 to 32 and 46 to 54 wk of age). The trials were designed as dose-response studies where isoleucine-deficient basal rations with 11.4 MJ metabolizable energy per kilogram were supplemented with varying amounts of L-isoleucine. In the production trials, dietary isoleucine concentrations ranged from 0.37 to 1.05%. In the three production trials, maximum daily egg mass was achieved at dietary isoleucine concentrations of between 0.39 and 0.75% (25 to 32 wk of age, daily egg mass 53 g), 0.40 and 0.57% (24 to 32 wk of age, daily egg mass 57 g), and 0.40 and 0.81% (46 to 54 wk of age, daily egg mass 56 g). The corresponding ranges of daily isoleucine intakes were 412 to 770 mg, 436 to 624 mg, and 431 to 874 mg. In the nitrogen balance trial, maximum total nitrogen retention was achieved at dietary isoleucine concentrations of between 0.43 and 0.57%. Dietary isoleucine concentrations higher than 0.8% caused a reduction in hen BW. Dietary isoleucine concentrations higher than 1.0% additionally caused a reduction in the daily egg mass. The study thus shows that the margin between requirement and excess of isoleucine is narrow in laying hens.

Requirement of tryptophan in relation to the supply of large neutral amino acids in laying hens.

The present study was undertaken to find out whether the tryptophan requirement of laying hens is influenced by the supply of large neutral amino acids (LNAA). A factorial experiment was performed in which the dietary tryptophan concentration was varied at six different levels (1.0, 1.25, 1.5, 1.75, 2.0, and 2.5 g tryptophan/kg diet). As the second factor, the dietary concentrations of LNAA (isoleucine, valine, leucine, phenylalanine, and tyrosine) were varied at two levels. The first level provided an adequate supply of these amino acids; at the second level the concentrations of these amino acids were 40% higher than at the first level. The tryptophan requirement was estimated by a broken-line model and an exponential model of regression analysis. The tryptophan intake required for optimum (100% of maximum in the broken-line model, 95% of the maximum in the exponential model) egg production and daily egg mass was lower in hens fed the diets with high LNAA concentrations (145 and 155 mg/hen per day, respectively, in average of both models) than in hens fed the diets with adequate concentrations of LNAA (184 and 198 mg/hen per day, respectively, in average of both models). In contrast, the tryptophan requirement for optimum BW gain was lower in hens fed the diets with adequate LNAA concentrations (178 mg tryptophan per day) than in hens fed the diets with a high concentration of LNAA (212 mg tryptophan per day). In conclusion, the study suggests that an interaction between dietary LNAA and tryptophan exists in laying hens.

Lipid concentrations of fillets, liver, plasma and lipoproteins of African catfish, Clarias gariepinus (Burchell 1822), fed diets with varying protein concentrations.

This study investigated the effect of the dietary protein concentration on lipid concentrations in fillet and liver and concentrations of lipids in plasma and lipoproteins in African catfish. Two experiments were carried out, in which African catfish were fed diets with various protein concentrations. In experiment 1, semisynthetic diets with various concentrations of casein (350, 450 or 550 g protein/kg) were used. In experiment 2, diets were based on a commercial trout diet supplemented with various amounts of casein or carbohydrates, resulting in protein concentrations between 282 and 545 g/kg diet. In both experiments, the dietary protein concentration had a significant effect on growth, feed conversion ratio and carcass composition. Maximum of body weight gains and feed efficiency ratios were reached in both experiments at the highest dietary protein concentrations. Increasing the dietary protein concentration continuously increased masses of fillets and reduced masses of the liver and adipose tissue in the abdominal cavity. Fish fed the diets with the highest protein concentrations had the lowest concentration of total lipids, triglycerides and cholesterol in the fillets, the highest percentage of polyunsaturated fatty acids (PUFA) in total lipids of fillets and the lowest concentrations of saturated fatty acids (SFA). Fish fed the diets with the highest protein concentration also had the lowest concentrations of triglycerides in the liver, the highest percentages of PUFA in liver total lipids and the lowest percentages of SFA. Moreover, fish fed diets with high protein concentrations (501 and 545 g/kg) had significantly lower concentrations of triglycerides, cholesterol and phospholipids in plasma than fish fed diets with lower protein concentrations. In conclusion, this study shows that the dietary protein concentration does not only influence growth, feed efficiency and carcass composition in African catfish, but also influences their lipid metabolism and lipid concentrations of liver and fillet.

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. 14 MJ 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 tryptophan 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.

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.