Increasing dispensable amino acids in diets of kittens fed essential amino acids at or below their requirement increases the requirement for arginine

Summary Kittens fed diets containing 0.75 × the NRC (1986) essential amino acid requirement (EAArq) and 210 to 560g crude protein(CP)/kg diet exhibited, with increasing CP: 1) decreasing weight gain, 2) decreasing plasma arginine concentrations, 3) increasing urinary orotic acid excretion, 4) increasing plasma glutamic acid concentrations, and 5) plasma isoleucine concentrations at levels that suggest a marginal isoleucine deficiency. Kittens fed a control diet (CD) containing 1.5 × EAArq and 350 g CP/kg diet had maximal weight gains and no orotic aciduria. It was concluded that the decreased weight gain and adverse metabolic effects were caused by arginine deficiency and possibly glutamic acid toxicity induced by high dietary dispensable amino acids. Kittens fed the diets containing 1.0 × EAArq and 350 and 560 g CP/kg diet had depressed plasma arginine and elevated glutamic acid concentrations and orotic aciduria. These results indicate that 10 g arg/kg diet is not adequate at CP concentrations above 280 g/kg and the calculated requirement of arginine is (0.02 g arginine/g CP) × (Y g CP/kg diet) + (4.0 g arginine/kg diet) where Y is the dietary CP level.Abbreviations CD control diet - CP crude protein (g CP/kg diet = g nitrogen/kg diet × 6.25) - DAA dispensable amino acids - EAA essential amino acids - EAArq essential amino acid requirement     

Dietary arginine requirement of fingerling Indian major carp,Labeo rohita (Hamilton) based on growth,nutrient retention efficiencies,RNA/DNA ratio and body composition

To quantify the optimum dietary arginine requirement of fingerling Indian major carp, Labeo rohita (4.10 ± 0.04 cm; 0.62 ± 0.02 g), an 8‐week growth trial was conducted in eighteen 70‐L indoor circular aqua‐coloured troughs provided with a flow‐through system at 28 ± 1°C. Isonitrogenous (40 g 100 g^?1 crude protein) and isocaloric (4.28 kcal g^?1 gross energy) amino acid test diets containing casein and gelatin as intact protein sources with graded levels of arginine (0.5, 0.75, 1.0, 1.25, 1.50 and 1.75 g 100 g^?1 dry diet) were fed to triplicate groups of fish to apparent satiation at 07:00, 12:00 and 17:30 hours. Growth performance of fish fed the above diets was evaluated on the basis of absolute weight gain (AWG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE) and energy retention efficiency (ERE). Maximum AWG (2.61), SGR (2.80), best FCR (1.35), highest PER (1.85), PRE (37%) and ERE (76%) were recorded at 1.25 g 100 g^?1 dietary arginine. Maximum body protein (18.88 g 100 g^?1) and RNA/DNA ratio (5.20) were also obtained in a 1.25 g 100 g^?1 arginine dry diet. Except for the reduced growth performance in fish fed arginine‐deficient diets, no other deficiency signs were apparent. Based on the broken‐line and second‐degree polynomial regression analysis of the AWG, SGR, FCR, PER, PRE and ERE data, the optimum arginine requirement for fingerling Labeo rohita was found to be in the range of 1.22–1.39 g 100 g^?1 of the dry diet, corresponding to 3.05–3.47 g 100 g^?1 of dietary protein.     

Maximal growth occurs at a broad range of essential amino acids to total nitrogen ratios in kittens

Summary Kittens fed diets containing 2.0 and 3.0 times (X) the NRC (1986) essential amino acid (EAA) requirement (EAArq) and 210 to 560g crude protein (CP)/kg diet had growth rates and plasma amino acid patterns that were not significantly different than kittens fed a control diet (CD) containing 1.5 X EAArq and 350 g CP/kg diet. Growth rates of kittens fed diets containing only EAA (with nontoxic levels of arginine and methionine) and 280 to 460 g CP/kg diet were equivalent to those of kittens fed CD. Kittens fed only EAA and 140 and 210 g CP/kg diet had growth rates that were significantly lower than kittens fed CD. Since the growth rate of kittens fed 1.5X EAArq and 210 g CP/kg diet in a previous experiment was equivalent to kittens fed CD (Taylor et al., 1997), it is suggested that the requirement for CP is higher (up to 280 g CP/kg diet) when only EAA are fed. The higher crude protein requirement appears to be primarily a consequence of the high obligatory nitrogen loss as urea (especially from arginine) incurred in the conversion of nitrogen from EAA to dispensable amino acids in the liver and secondarily because of a slow rate of catabolism of the EAA. A 3-dimensional plot of weight gains vs. CP levels and EAA to total nitrogen (E: T) ratios of kittens shows a broad range of CP levels and E: T ratios that support optimal growth in the kitten. It is suggested that similar patterns would occur in the chick, rat and other species if adverse effects caused by excesses of specific amino acids are avoided.Presented in part at the Biology '96 Meeting in Washington, DC [Taylor TP, Deberry J, Morris JG, Rogers QR (1996) Effects of dietary nitrogen level and essential amino acid: total nitrogen (E: T) ratio on kitten weight gain. FASEB J 10: A737 (abs. 4259)] and in part at the Proceedings of the Waltham International Symposium, Pet Nutrition and Health in the 21st Century, Orlando, Florida, USA [Rogers QR, Taylor TP, Morris JG (1997) Optimizing dietary amino acid patterns at various levels of crude protein for the cat. J Nutr (abs.) (in press).     

Dietary protein, energy and arginine affect LAT1 expression in forebrain white matter differently

L-type amino acid transporter-1 (LAT1) transports large, branched-chain, aromatic and neutral amino acids. About 64 Duroc × Landrace × Yorkshire pigs were used to study the effects of dietary crude protein (CP), energy and arginine on LAT1 expression in forebrain. The results showed that LAT1 expression in forebrain was sensitive to different levels of CP, energy and arginine. On the basis of Western blot analysis, a lower level of LAT1 presented in the brain tissues of pigs fed the low dietary CP diet (P < 0.05), a higher level were found in pigs fed the higher CP diet, with moderate to intense staining seen in pigs fed the diet plus 1% arginine. In contrast, pigs fed the control-energy diet had weak LAT1 expression, and those fed the diet supplemented with 1% arginine showed lowest LAT1 expression (P < 0.05). These results showed that LAT1 was highly expressed in the forebrain, and expression of LAT1 was affected by dietary protein, energy and arginine differently.     

Molecular cloning of chicken hepatic histidase and the regulation of histidase mRNA expression by dietary protein

Chicken hepatic histidase activity varies with dietary protein consumption, but the mechanisms responsible for this alteration in activity are unclear. In the present research, the complete coding sequence and deduced amino acid sequence for chicken histidase was determined from clones isolated from a chicken liver cDNA library. The deduced amino acid sequence of chicken histidase has greater than 85% identity with the amino acid sequences of rat, mouse, and human histidase. In a series of four experiments, broiler chicks were allowed free access for 1.5, 3, 6, or 24 h to a low (13 g/100 g diet), basal (22 g/100 g diet) and high (40 g/100 g diet) protein diet. In the final experiment 5, chicks were allowed free access for 24 h to the basal, high protein diet or the basal diet supplemented with three different levels of l-histidine (0.22 g/100 g diet, 0.43 g/100 g diet or 0.86 g/100 g diet). There were no differences in the expression of the mRNA for histidase at 1.5 h, but at 3 h, histidase mRNA expression was significantly (P < .05) greater in chicks fed the high protein diet compared to chicks fed the low protein diet. At 6 and 24 h, histidase mRNA expression was significantly enhanced in chicks fed the high protein diet, and significantly reduced in chicks fed the low protein diet, compared with chicks fed the basal diet. Histidase mRNA expression was not altered by supplementing the basal diet with histidine. The results suggest that previously observed alterations in the activity of histidase, which were correlated to dietary protein intake, are mediated by rapid changes in the mRNA expression of this enzyme, and are not necessarily related to dietary histidine intake.     

Effects of dietary sulfur amino acids and crude protein on the performance of finishing broilers

The effects of different combinations of dietary methionine+cystine (Met+Cys) and dietary crude protein (CP) in finishing broilers were investigated in two growth studies. In Exp. 1, male broilers 29 to 42 days of age were fed 18 diets containing 16.9%, 18.7%, or 20.4% CP with six levels of Met+Cys within each protein level. Similarly, in Exp. 2 another 12 diets containing either 18.0 or 21.5% CP were fed to male broilers 29 to 48 days of age.

In general, the Met+Cys requirement for optimum feed conversion was higher than for maximum growth. In both experiments, between 0.80% and 0.85% methionine+cystine optimized feed conversion. These dietary levels were valid for a 13.05 MJ ME/kg diet fed to broilers growing from 1.2 kg to 2.2 kg (Exp. 1), or for a 13.60 MJ ME/kg diet fed to broilers growing from 1.3 kg to 3.0 kg (Exp. 2).

The Met+Cys requirement was not consistently affected by the dietary CP content in Exp. 1. In Exp. 2, increasing dietary CP from 18.0% to 21.5% tended to increase the Met+Cys requirement for optimum feed conversion.

A dietary CP level of 18.0% to 18.7% supported performance and carcass fat deposition equal to diets containing 20.4% or 21.5% CP, respectively, when the sulfur amino acid content was adequate.     

Lysine and arginine requirements of juvenile Asian sea bass (Lates calcarifer)

Two separate experiments were conducted to determine the dietary requirements of juvenile Asian sea bass Lates calcarifer Bloch for lysine and arginine. Fish (average initial weight: lysine experiment, 13.12 ± 0.12 g; arginine experiment, 2.56 ± 0.13 g) were given amino acid test diets for 12 weeks containing fish meal, zein, squid meal, and crystalline amino acids. Each set of isonitrogenous and isocaloric test diets contained graded levels of L ‐lysine or L ‐arginine. The feeding rate in the lysine experiment was at 4–2.5% of the body weight day^?1, while in the arginine experiment it was at 10–4% of the body weight day^?1. The fish (20 per tank, lysine experiment; 15 per tank, arginine experiment) were reared in 500‐L fibreglass tanks with continuous flowthrough sea water at 27 °C and salinity of 31 ppt in the lysine experiment and at 29 °C and salinity of 29 ppt in the arginine experiment. The experiments were in a completely randomized design with two replicates per treatment. Survival was high in fish given adequate lysine or arginine. Mean percentage weight gains were significantly different in fish fed varying levels of lysine or arginine. Fish fed high levels of L ‐arginine suffered high mortalities. No significant differences were obtained in the feed efficiency ratios (FER, g gain g^?1 feed) of fish fed graded lysine, although the values tended to increase as the dietary lysine level was increased up to the requirement level. In contrast, in the arginine experiment, significant differences in FER of fish among treatments were obtained; the highest FER was observed in fish fed the diet containing an optimum arginine level. On the basis of the growth response, survival, and FER, the lysine and arginine requirements of juvenile Asian sea bass were estimated to be 20.6 g kg^?1 dry diet (4.5% protein) and 18.2 g kg^?1 dry diet (3.8% protein), respectively. These data will be useful in the further refinement of practical diet formulations for the Asian sea bass.     

The influence of sulphur,molybdenum and cadmium exposure on the growth of goat,cattle and pig

A three factorial designed feeding experiment with common carp (Cyprinus carpio L.) was carried out in an intensive experimental rearing system. Fish (initial body weight 200 g) were fed on two different levels of dietary energy (16 and 18 MJ DE/kg DM), two different levels of protein (320 and 420 g CP/kg DM) and also two different feeding intensities (100% and 75% of the maximum intake). The experiment was terminated when fish reached a mean body weight of 1300 g.

Growth, feed utilization and nutrient composition of the whole body and fillet were observed. The highest growth was obtained when the fish were fed on the diet containing high dietary energy and high dietary protein with satiation feeding. High dietary energy, high dietary protein and restriction of feed intake improved feed conversion ratios. High dietary energy, low dietary protein and restrictive feeding increased energy utilization. Low dietary protein and restrictive feeding resulted in better protein utilization.

Fish fed with high dietary energy contained more fat and less protein in their carcasses. A lower fat content but higher protein and higher ash content in fish carcasses was shown when fish were fed with a diet high in protein and fed restrictively.     

Limiting amino acids in dried microbial cells given to young turkeys

The effects of amino acid additions to diets containing methanol-grown dried microbial cells (MC) have been examined in two experiments with young turkeys. The sample of MC used was an early pelleted preparation of Methylophilus methylotrophus produced by Imperial Chemical Industries in the initial stages of the development of Pruteen. The pellets were crushed to a coarse powder prior to dietary inclusion. In the first study, turkeys fed on either 100 or 200 g MC/kg diet with supplements of methionine had similar growth rates and efficiency of food conversion as those fed on a control soya bean meal (SBM) diet containing equivalent dietary nitrogen concentrations (54 g N/kg DM). Combined additions of methionine and arginine to the MC diets had no further effect on growth performance. In the second experiment, an unsupplemented basal diet containing 150 g MC/kg diet and 55 g N/kg DM supported marginally better weight gain, efficiency of food utilisation and efficiency of carcass deposition of gross energy (GE) and N than a basal SBM diet with 53 N/kg DM. Methionine supplementation of the latter diet improved growth performance to levels approaching those in the group fed on the basal MC diet. Feeding the basal SBM and MC diets containing sub-optimal levels of dietary N (46 and 48 g N/kg DM, respectively) confirmed the slightly superior nutritional value of the MC diet. Methionine supplementation enhanced growth performance and efficiency of carcass deposition of N and GE in turkeys fed on the SBM diet. On the other hand, methionine supplementation of the corresponding basal diet containing MC induced only slight improvements in growth and efficiency of deposition of N and GE in the carcass. Combined additions of methionine and lysine to the N-restricted diets containing SBM or MC were less effective than the addition of methionine alone.     

An interaction between dietary silicon and arginine affects immune function indicated by con-A-induced DNA synthesis of rat splenic T-lymphocytes

Sporadic reports have appeared that suggest silicon plays a functional role in immune function by affecting lymphocyte proliferation. In addition, there is also considerable interest in supplemental arginine as a modulator of immune function. Therefore, the purpose of this animal experiment was to determine the effect of supplemental compared to adequate arginine on immune function as measured by splenic T-lymphocyte proliferation in the presence of adequate or inadequate dietary silicon. The independent variables were, per gram of fresh diet, silicon supplements of 0 or 35 μg and arginine supplements of 0 or 5 mg. The basal diet contained 2.3 μg silicon/g and 7.82 mg l-arginine/g. After feeding the male rats (nine per treatment group) for 8 wk, spleen lymphoid cells were isolated and cultured with methyl-³[H]thymidine. Supplemental arginine significantly decreased Con-A-induced DNA synthesis of splenic T-lymphocytes, but the response to arginine was influenced by dietary silicon. The decreased DNA synthesis was more marked when rats were fed adequate silicon than when fed inadequate silicon. Also, when arginine was not supplemented, DNA synthesis was higher in lymphocytes from rats fed an adequate silicon diet than rats fed the inadequate silicon diet. These findings support the hypothesis that an interaction between silicon and arginine affects immune function and that inadequate dietary silicon impairs splenic lymphocyte proliferation in response to an immune challenge. The U.S. Department of Agriculture, Agricultural Research Service, Northern Plains Area is an equal opportunity/affirmative action employer, and all agency services are available without discrimination. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.     

Effect of dietary protein level on carcass traits and meat properties of Cinta Senese pigs

The aim of this study was to test the effect of various dietary protein contents (CP) on the carcass traits and the meat quality of Cinta Senese pigs. A total of 60 Cinta Senese pigs were equally distributed in four dietary groups that were balanced for sex (barrows and gilts) and live weight. The animals in the groups were fed one of four diets (80CP, 100CP, 130CP and 160CP) containing different CP contents (80, 100, 130 and 160 g/kg, respectively). The diets were administered to the pigs during the entire growing–fattening period in a controlled dose of 90 g/kg W^0.75, to a maximum of 2.5 kg/day per animal. The duration of the trial was ~250 days, ending when the animals reached the target slaughter weight of 145 kg. The 80CP diet produced fatter carcasses than did the other diets; no differences in carcass composition were found among the animals fed the other three diets (total lean cuts: 57.4%, 61.4%, 60.8% and 61.3% for 80CP, 100CP, 130CP and 160CP diet, respectively). The sample joint composition confirmed the highest fatness and the lowest meatiness of pigs fed 80CP. This same pattern was evident for the composition of the muscle (Longissimus lumborum) containing the largest amount of i.m. fat, and the lowest protein content in the 80CP group. Moreover, the 80CP diet resulted in the lightest and yellowest meat with the highest cooking loss. A principal component analysis of the physical and chemical traits of the meat revealed three first factors that explained 56% of the total variance. Among them, only the intersection of Factor1, which combined mainly lower pH at 24 h postmortem and higher drip loss, cooking loss, lightness and yellowness, with Factor2, which associated higher toughness, higher protein and lower fat content, graphically appeared to discriminate the 80CP diet from the other ones. In conclusion, a diet with 80 g/kg of CP content was inadequate for this local breed, while, in consideration of the cost of protein feed and the need to reduce N pollution, the 100CP diet would be an optimal compromise for the growth–fattening of Cinta Senese pigs.     

Effects of dietary arginine levels on growth performance and body composition of juvenile grouper Epinephelus coioides

An 8‐week feeding trial was conducted to determine the effects of dietary arginine levels on growth performance and body composition of juvenile grouper Epinephelus coioides (initial weight: 16.10 ± 0.26 g per fish) in 500‐L indoor flow‐through circular fiberglass tanks. Diets contained six levels of l ‐arginine ranging from 1.78% to 3.31% of dry diet in 0.30% increments. The diets, in which 25% crude protein came from fishmeal and soybean protein concentrate, and 23% from crystalline amino acids, were formulated to simulate the amino acid profile of 48% whole chicken egg protein except for arginine. Each diet was assigned to three tanks (20 fish per tank) in a completely randomized design. Grouper were fed to apparent satiation (about 5% body weight per day at the initial 1–4 weeks and 3% body weight per day in the following 5–8 weeks) twice daily on weekdays and once daily on weekends. Weight gain (WG) and specific growth rate (SGR) showed an incremental trend with increasing dietary arginine levels from 1.78% to 2.72% and remained thereafter relatively constant. Productive protein value (PPV) was poorest in fish fed the lowest arginine diet (P < 0.05) and showed no significant differences among other treatments (P > 0.05). Dietary arginine contents significantly influenced body composition. With the increase in dietary arginine, contents of total essential amino acids (EAAs), total non‐EAAs and total amino acids of whole body significantly increased (P < 0.05). The retention of dietary EAA in whole body of juvenile grouper was significantly influenced by dietary arginine. Arginine retention increased with increasing dietary arginine levels from 1.78% to 2.72%, then declined above the level of 2.7% (P < 0.05). Based on broken‐line regression analysis of WG against dietary arginine levels, the dietary arginine requirement of juvenile grouper E. coioides was determined as 2.7% of the diet (corresponding to 5.5% of dietary protein).     

Arginine synthesis does not occur during first-pass hepatic metabolism in the neonatal piglet

We have shown that first-pass intestinal metabolism is necessary for approximately 50% of whole body arginine synthesis from its major precursor proline in neonatal piglets. Furthermore, the intestine is not the site of increased arginine synthesis observed during dietary arginine deficiency. Primed constant intravenous (iv) and intraportal (ip) infusions of L-[U-14C]proline, and iv infusion of either L-[guanido-14C]arginine or L-[4,5-3H]arginine were used to measure first-pass hepatic arginine synthesis in piglets enterally fed either deficient (0.20 g.kg(-1).day(-1)) or generous (1.80 g.kg(-1).day(-1)) quantities of arginine for 5 days. Conversion of arginine to other urea cycle intermediates and arginine recycling were also calculated for both dietary treatments. Arginine synthesis (g.kg(-1).day(-1)) from proline was greater in piglets (P < 0.05) fed the deficient arginine diet in both the presence (generous: 0.07; deficient: 0.17; pooled SE = 0.01) and absence (generous: 0.06; deficient: 0.20; pooled SE = 0.01) of first-pass hepatic metabolism. There was no net arginine synthesis from proline during first-pass hepatic metabolism regardless of arginine intake. Arginine conversion to urea, citrulline, and ornithine was significantly greater (P < 0.05) in piglets fed the generous arginine diet. Calculated arginine fluxes were significantly lower (P = 0.01) for [4,5-3H]arginine than for [guanido-14C]arginine, and the discrepancy between the values was greater in piglets fed the deficient arginine diet (35% vs. 20%). Collectively, these findings show that first-pass hepatic metabolism is not a site of net arginine synthesis and that piglets conserve dietary arginine in times of deficiency by decreasing hydrolysis and increasing recycling.     

Estimates of dietary threshold levels for crude protein and amino acids to obtain plateau values of apparent ileal crude protein and amino acid digestibilities in newly weaned pigs

This study was conducted to estimate dietary threshold levels for crude protein (CP) and amino acids (AA) at which apparent ileal digestibilities (AID) of CP and AA in assay diets for newly weaned pigs reach plateaus. A total of 14 (12 + 2 for replacement) three-week old barrows were fitted with simple T cannulas at the distal ileum. Corn starch-based diets containing six graded levels of CP from casein, 90, 155, 220, 285, 350, or 415 g CP/kg assay diet (as-fed), were formulated. At 28 days of age, the pigs were randomly allocated to the six dietary treatments with two pigs per CP level in four weekly repeated measurement periods. They were fed twice daily a total of 30 g (as-fed) per kg of individual body weight at 8:00 and 20:00 h. The dietary CP and AA levels affected AID of CP and most AA (p = 0.005 to p = 0.040) in the assay diets. The AID of CP and AA were higher at 155 and 220 compared to 90 g CP/kg assay diet (p < 0.001 to p = 0.047). Initially, the AID of CP and AA increased sharply then gradually reached, at individual break points (p < 0.001 to p = 0.047), their plateaus (p < 0.001), which did not change up to dietary CP levels of 415 g/kg assay diet and the AID values became independent of the dietary AA levels. The piglets' capacity to digest CP and absorb AA was not limiting under these experimental conditions. There was no effect of age on AID of CP and AA (p = 0.056 to p = 0.899) except for a linear increase (p = 0.045) in AID of glycine from Period 1 to 4. Segmented quadratic with plateau relationships between the AID of CP and AA and their dietary contents were fitted for CP and each AA. The lower end points of 95% confidence intervals of the plateau AID values were defined to represent the initial plateau AID. The dietary CP and AA contents, corresponding to the initial plateau AID values, represent the dietary threshold levels. For CP and the indispensable amino acids, the plateau AID [%] and the dietary threshold levels [g/kg DM], respectively, in casein were: CP, 94.2 and 176; arginine, 95.1 and 7; histidine, 96.0 and 5; isoleucine, 96.4 and 8; leucine, 96.8 and 16; lysine, 96.8 and 12; methionine, 97.9 and 5; phenylalanine, 96.2 and 10; threonine, 93.4 and 9; tryptophan, 94.3 and 2; valine, 95.9 and 11. For the determination of plateau AID in piglets, the crude protein and amino acid contents in the assay diets should meet or exceed the corresponding dietary threshold levels.     

Effect of low-protein amino acid-supplemented diets on the growth performance, gut morphology, organ weights and digesta characteristics of weaned pigs

A 21-day study was conducted to determine whether isoleucine might limit the performance of piglets fed low-crude protein (CP), amino acid (AA)-supplemented diets and to investigate the potential benefits of low-CP diets on gastrointestinal health in weaned pigs. Ninety-six piglets (initial BW = 6.44 ± 0.14 kg), housed four per pen, were randomly assigned to one of four diets, resulting in six replicate pens per diet. Dietary treatments were as follows: (1) 210 g/kg CP diet, (2) 190 g/kg CP diet deficient in isoleucine, (3) 190 g/kg CP diet supplemented with crystalline isoleucine up to the level in the 210 g/kg CP diet and (4) 170 g/kg CP diet supplemented with isoleucine and valine on the ideal protein ratio basis (60% and 70% relative to lysine, respectively). Pigs were allowed to adapt to the new environment for 4 days before the experiment commenced. Overall, pigs fed the 210 g/kg CP diet had higher (P < 0.05) average daily gain and lower (P < 0.05) feed : gain ratio compared with those fed the other diets. The faecal consistency score of pigs fed the 210 g/kg CP diet was higher (P < 0.05) than those fed the other diets. Pigs fed the 170 g/kg diet had lower (P=0.02) small intestine weight than those fed the 210 g/kg CP diet. Pigs fed the 210 g/kg CP diet had deeper (P < 0.05) crypt in the duodenum and ileum and higher (P < 0.05) ammonia N concentration in caecal digesta than those fed the other diets. There were no effects of diet on microbial population and volatile fatty acid concentration in the caecal digesta except for propionic acid whose concentration was higher (P < 0.05) for pigs fed the 170 g/kg diet than those fed the 190+isoleucine and the 210 g/kg CP diets. The results indicate that the low-CP, AA-supplemented diet reduced crypt hypertrophy, ammonia N concentration in the caecal digesta, small intestine weight and the performance of piglets. Also, the results of the current study were inconclusive with respect to whether isoleucine may limit the performance of pigs fed a low-CP, AA-supplemented diet.     

Effects of keratinase supplementation of corn-soybean meal based diets on apparent ileal amino acid digestibility in growing pigs and serum amino acids, cytokines, immunoglobulin levels and loin muscle area in nursery pigs

Two experiments were conducted to evaluate effects of keratinase for growing and nursery pigs. In Exp. 1, six pigs (32.3 +/- 2.8 kg body weight), fitted with a simple T-cannula at the distal ileum, were assigned to one of two 3 x 3 Latin squares involving three periods and three diets including a basal diet and the same diets supplemented with 0, 0.05 or 0.1% keratinase. Dietary keratinase supplementation increased the apparent ileal digestibility of crude protein (CP), arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, alanine, glutamic acid and proline (p < 0.05). Digestibility coefficients did not differ between pigs fed 0.05 and 0.1% keratinase. In Exp. 2, 24 piglets weaned at 30 +/- 2 d of age were used in a 2 x 2 factorial design experiment with two CP concentrations (19 vs. 22%) and two levels of keratinase supplementation (0 vs. 0.05%). Keratinase supplementation increased (p < 0.05) average daily gain, serum arginine concentration and loin muscle area but decreased (p < 0.05) serum interleukin-10 concentrations. The reduction in dietary CP level decreased (p < 0.05) serum urea nitrogen concentrations, isoleucine, serine and proline concentrations, but increased serum arginine concentrations. Few interactions between keratinase supplementation and dietary CP concentration were observed. This study indicated that dietary keratinase supplementation improved apparent ileal amino acid digestibility for growing pigs and had a positive effect on weight gain, immune response and loin muscle area for nursery pigs.     

Sulphur amino acid requirement of juvenile Asian sea bass Lates calcarifer

The dietary requirement of juvenile Asian sea bass Lates calcarifer Bloch for total sulphur amino acids was studied. Fish (average initial weight of 2.59 ± 0.08 g) were reared in twelve 500 L fibreglass tanks provided with flow-through seawater at 26°C and salinity of 31 p.p.t. for 12 weeks. They were fed semi-purified test diets containing 6.2, 7.2, 8.1, 9.0, 10.8, or 12.6 g methionine kg⁻¹ dry diet and a basal level of 3.1 g cystine kg⁻¹ dry diet. The mean crude protein of the diets (containing defatted Peruvian fishmeal, squid meal, soybean meal, and free amino acid mixture to simulate the pattern of hydrolysed sea bass protein) was 46.02%. The crude fat content of the diets was 10.51% from a 1 : 1 mixture of cod liver oil and soybean oil. Survival was 100% in all treatments. On the basis of the growth response, the total sulphur amino acid requirement of juvenile Asian sea bass was estimated to be 13.4 g kg⁻¹ dry diet (2.9% of protein). Fish fed low levels of l -methionine had significantly lower weight gains and feed efficiency ratios as well as slightly higher hepatosomatic indices. No nutritional deficiency signs were observed other than growth depression in fish fed on diets that were low in methionine. This information is valuable in further refinement of formulations of practical diets for the Asian sea bass.     

Daily delivery of dietary nitrogen to the periphery is stable in rats adapted to increased protein intake

Dietary nitrogen was traced in rats adapted to a 50% protein diet and given a meal containing 1.50 g (15)N-labeled protein (HP-50 group). This group was compared with rats usually consuming a 14% protein diet and fed a meal containing either 0.42 g (AP-14 group) or 1.50 g (AP-50 group) of (15)N-labeled protein. In the HP group, the muscle nonprotein nitrogen pool was doubled when compared with the AP group. The main adaptation was the enhancement of dietary nitrogen transferred to urea (2.2 +/- 0.5 vs. 1.3 +/- 0.1 mmol N/100 g body wt in the HP-50 and AP-50 groups, respectively). All amino acids reaching the periphery except arginine and the branched-chain amino acids were depressed. Consequently, dietary nitrogen incorporation into muscle protein was paradoxically reduced in the HP-50 group, whereas more dietary nitrogen was accumulated in the free nitrogen pool. These results underline the important role played by splanchnic catabolism in adaptation to a high-protein diet, in contrast to muscle tissue. Digestive kinetics and splanchnic anabolism participate to a lesser extent in the regulation processes.     

Reducing protein content in the diet of growing goats: implications for nitrogen balance,intestinal nutrient digestion and absorption,and rumen microbiota

Reducing dietary CP content is an effective approach to reduce animal nitrogen excretion and save protein feed resources. However, it is not clear how reducing dietary CP content affects the nutrient digestion and absorption in the gut of ruminants, therefore it is difficult to accurately determine how much reduction in dietary CP content is appropriate. This study was conducted to investigate the effects of reduced dietary CP content on N balance, intestinal nutrient digestion and absorption, and rumen microbiota in growing goats. To determine N balance, 18 growing wether goats (25.0 ± 0.5 kg) were randomly assigned to one of three diets: 13.0% (control), 11.5% and 10.0% CP. Another 18 growing wether goats (25.0 ± 0.5 kg) were surgically fitted with ruminal, proximate duodenal, and terminal ileal fistulae and were randomly assigned to one of the three diets to investigate intestinal amino acid (AA) absorption and rumen microbiota. The results showed that fecal and urinary N excretion of goats fed diets containing 11.5% and 10.0% CP were lower than those of goats fed the control diet (P < 0.05). When compared with goats fed the control diet, N retention was decreased and apparent N digestibility in the entire gastrointestinal tract was increased in goats fed the 10% CP diet (P < 0.05). When compared with goats fed the control diet, the duodenal flow of lysine, tryptophan and phenylalanine was decreased in goats fed the 11.5% CP diet (P < 0.05) and that of lysine, methionine, tryptophan, phenylalanine, leucine, glutamic acid, tyrosine, essential AAs (EAAs) and total AAs (TAAs) was decreased in goats fed the 10.0% CP diet (P < 0.05). When compared with goats fed the control diet, the apparent absorption of TAAs in the small intestine was increased in goats fed the 11.5% CP diet (P < 0.05) and that of isoleucine, serine, cysteine, EAAs, non-essential AAs, and TAAs in the small intestine was increased in goats fed the 10.0% CP diet (P < 0.05). When compared with goats fed the control diet, the relative richness of Bacteroidetes and Fibrobacteres was increased and that of Proteobacteria and Synergistetes was decreased in the rumen of goats fed a diet with 10.0% CP. In conclusion, reducing dietary CP content reduced N excretion and increased nutrient utilization by improving rumen fermentation, enhancing nutrient digestion and absorption, and altering rumen microbiota in growing goats.     

Effects in chicks of arsenic,arginine, and zinc and their interaction on body weight,plasma uric acid,plasma urea,and kidney arginase activity

The interaction among arsenic, zinc, and arginine was studied in chicks using two fully crossed, three-way, two-by-two-by-two experiments. Arsenic at levels of 0 and 2 μg/g zinc at levels of 2.5 (zinc-deficient) and 25 (zinc-adequate) μg/g, and arginine at levels of 0 and 16 mg/g were supplemented to the diet. After 28 d in both experiments, growth was depressed in chicks fed diets either supplemented with arginine or deficient in zinc. Arsenic deprivation depressed growth of chicks fed diets containing the basal level of arginine and 25 μg supplemental Zn/g. Arsenic deprivation had little or no effect on growth of zinc-deprived chicks fed diets containing the basal level of arginine, or in zinc-deprived or zinc-adequate chicks fed supplemental arginine. Zinc-deficiency elevated urea in plasma and arginase activity in kidney. Those elevations, however, were more marked in arsenic-supplemented than in arsenic-deprived chicks. Also, plasma urea and kidney arginase activity were markedly elevated in chicks fed supplemental arginine; the elevations were more marked in zinc-deficient chicks. These findings support the concept that arsenic has a physiological role, associated with zinc, that can influence arginine metabolism in the chick.