Investigations on Genetically Modified Maize (Bt-Maize) in Pig Nutrition: Chemical Composition and Nutritional Evaluation

The objective of the present study was to determine the composition and the nutritional value of parental and transgenic maize seeds fed to pigs. The parental maize line was genetically modified to incorporate a gene from Bacillus thuringiensis (Bt) expressing a toxin against the European corn borer (Ostrinia nubilalis). Both (parental and transgenic) maize lines were analyzed for crude nutrients, starch, sugar, non-starch polysaccharides (NSP), amino acids, fatty acids, as well as for selected minerals. Furthermore, four complete diets were mixed and were analyzed for the same nutrients and some selected ingredients. The diets contained 70% maize to attain a high effect level. To evaluate the feeding value of one variety of genetically modified maize (transgenic) compared to the feeding value of the unmodified maize (parental) line, a balance study with twelve pigs was designed. Three collecting periods were used for each maize line each with six animals. The collected faeces were analyzed for crude nutrients. All measured parameters were virtually the same ( e.g. crude protein 11.59% vs. 11.06% in DM), especially the digestibility of crude protein (85.8 ± 2.3% vs. 86.1 ± 1.8%), the amount of nitrogen-free-extract (92.8 ± 0.6% vs. 93.2 ± 0.6%) and the metabolizable energy (15.7 ± 0.2% vs. 15.8 ± 0.2% MJ/kg DM) for both maize lines. Compared to the parental line, the chemical composition and digestibility of crude nutrients and energy content were not significantly affected by the genetic modification of maize. Therefore, from the view of a nutritional assessment, the genetically modified maize can be regarded as substantially equivalent to the parental maize line.     

Digestibility of fractionated green biomass as protein source for monogastric animals

Globally, there is an increased demand for sustainable protein sources for animal feed. Grass and forage legumes have the yield potential to become such alternatives, but the protein needs to be separated from the fibres. Red clover, white clover, lucerne and perennial ryegrass were fractionated into a green juice and a fibrous pulp in a screw-press and protein was subsequently precipitated. The nitrogen (N) and amino acid composition of the produced fractions was analysed and the digestibility of dry matter (DM) and N was evaluated using a rat digestibility trial. The aim was to determine the effect of fractionation on composition and digestibility in order to evaluate the four plants as potential protein sources for monogastrics. Protein concentrates with CP concentrations of 240 to 388 g/kg DM and fibrous pulps with CP concentrations of 111 to 216 g/kg DM were produced. The sum of all analysed amino acids was highest in the protein concentrates corresponding to a low concentration of non-protein nitrogen ranging from 4.9% to 10.4%. Only small variations were seen in the amino acid compositions of the different plants and fractions. The concentration of the essential lysine and methionine in the protein concentrate ranged from 6.27 to 6.67 g/16 g N and 1.54 to 2.09 g/16 g N for lysine and methionine, respectively. For all plants species, total tract digestibility of DM and standardised N digestibility was significantly higher in the protein concentrates (60.8% to 76.5% and 75.4% to 85.0% for DM and N, respectively) compared to pulp (21.2% to 43.4% and 52.1% to 72.5% for DM and N, respectively). Digestibility of lucerne protein concentrate (76.5% and 85.0% for DM and N, respectively) was higher than of the unprocessed plant (39.6% and 74.9% for DM and N, respectively), whereas for red and white clover no difference was found. The amino acids methionine and cysteine were limiting for pigs and broilers in all fractions regardless of plant origin, and low scores were also found for lysine. The study demonstrated great potential of using green plants as a protein source for monogastrics because of high protein content, balanced amino acid composition and high digestibility of DM and N. The effects of processing and protein precipitation were pronounced in lucerne where significantly improved digestibility was observed in the protein concentrate. The results from the study provide valuable and enhanced knowledge to the production of alternative and sustainable protein sources for monogastric feed.     

Reducing dietary protein in dairy cow diets: implications for nitrogen utilization,milk production,welfare and fertility

In light of increasing global protein prices and with the need to reduce environmental impact of contemporary systems of milk production, the current review seeks to assess the feasibility of reducing levels of dietary CP in dairy cow diets. At CP levels between 140 and 220 g/kg DM there is a strong positive relationship between CP concentration and dry matter intake (DMI). However, such effects are modest and reductions in DMI when dietary CP is below 180 g/kg DM can be at least partially offset by improving the digestibility and amino acid profile of the undegradable protein (UDP) component of the diet or by increasing rumen fermentable energy. Level and balance of intestinally absorbable amino acids, in particular methionine and lysine, may become limiting at lower CP concentrations. In general the amino acid composition of microbial protein is superior to that of UDP, so that dietary strategies that aim to promote microbial protein synthesis in the rumen may go some way to correcting for amino acid imbalances in low CP diets. For example, reducing the level of NDF, while increasing the proportion of starch, can lead to improvements in nitrogen (N) utilisation as great as that achieved by reducing dietary CP to below 150 g/kg. A systematic review and meta-analysis of responses to rumen protected forms of methionine and lysine was conducted for early/mid lactation cows fed diets containing ⩽150 g CP/kg DM. This analysis revealed a small but significant (P=0.002) increase in milk protein yield when cows were supplemented with these rumen protected amino acids. Variation in milk and milk protein yield responses between studies was not random but due to differences in diet composition between studies. Cows fed low CP diets can respond to supplemental methionine and lysine so long as DMI is not limiting, metabolisable protein (MP) is not grossly deficient and other amino acids such as histidine and leucine do not become rate limiting. Whereas excess dietary protein can impair reproduction and can contribute to lameness, there is no evidence to indicate that reducing dietary CP levels to around 140 to 150 g CP/kg DM will have any detrimental effect on either cow fertility or health. Contemporary models that estimate MP requirements of dairy cows may require refinement and further validation in order to predict responses with low CP diets.     

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.     

Effects of mixtures of red clover and maize silages on the partitioning of dietary nitrogen between milk and urine by dairy cows

Eight multiparous lactating Holstein-Friesian cows were used to evaluate the partitioning of dietary nitrogen (N) from diets based on mixtures of red clover and maize silages in comparison with diets based on ryegrass silage. All cows received 4 kg/day of a standard dairy concentrate with one of four forage treatments in an incomplete changeover design with three 4-week periods. Three treatments were based on mixtures of red clover and maize silage. N intake was altered both by varying the ratio of these silages (40/60 and 25/75 on a dry matter (DM) basis) and by an additional treatment for which the DM intake of the 40/60 mixture was restricted to the level achieved with grass silage. Rumen passage rates were estimated from faecal excretion curves following a pulse oral dose of Dysprosium-labeled silage and urinary excretion of purine derivatives (PD) was used as an index of rumen microbial protein synthesis. Red clover silage mixtures led to significantly increased feed intake (21.5, 20.7 and 15.2 kg DM/day for 40/60 and 25/75 red clover/maize silage mixtures and grass silage, respectively), milk production (25.8, 27.8 and 20.0 kg/day for the same treatments, respectively) and milk component yields, but were without effect on milk fat and protein concentrations. The large increase in the yield of milk (24.5 kg/day) and milk components for the restricted red clover/maize silage treatment, in comparison with the grass silage treatment, was proportionately greater than the increase in DM intake (16.6 kg DM/day). There were no significant treatment effects on diet digestibility, while the higher intakes of red clover silage mixtures were associated with higher rumen passage rates (5.82%, 6.24% and 4.55%/h, respectively). There were significant effects of both N intake and forage source on the partitioning of dietary N between milk and urine. When dietary protein was diluted by the inclusion of maize silage, red clover silage led to increased milk N and reduced urinary N in comparison with grass silage. Improvements in N utilisation may be related to increased dietary starch and/or rumen passage rates leading to increased microbial protein synthesis for these treatments. Urinary excretion of PD was significantly higher for all diets based on mixtures of red clover and maize silages, in comparison with grass silage. Urinary N output was close to literature predictions based on N intake for the diet based on ryegrass silage, but 40 to 80 g/day (25% to 30%) less than predicted for the diets based on the mixtures of red clover and maize silages.     

Effect of offering dairy cows diets differing in phosphorus concentration over four successive lactations: 2. Health, fertility, bone phosphorus reserves and nutrient utilisation

This experiment examined the long-term effects of offering diets containing low levels of dietary phosphorus (P) on dairy cow health, fertility and bone composition, and the effect of dietary P level on nutrient utilisation. One hundred winter-calving Holstein-Friesian dairy cows were offered diets containing either 'high' or 'low' levels of dietary P over a 4-year period. Rations offered during the winter included grass silage, maize silage (70 : 30 dry matter (DM) basis, approximately) and concentrates (10.0 to 12.0 kg/cow per day). During the summer periods in years 1 and 2, half of the cows grazed both day and night, while the remaining cows grazed by day, and were housed by night and offered grass silage. During years 3 and 4, all cows grazed both day and night during the summer period. Concentrate feed levels during the summer periods were 3.0 to 4.0 kg/cow per day. Different dietary P levels were achieved by offering concentrates containing either high or low P levels during the winter period (approximately 7.0 or 4.4 g P/kg DM, respectively) and during the summer period (approximately 6.8 or 3.6 g P/kg DM, respectively). Total ration P levels averaged 4.9 and 3.6 g P/kg DM for the high and low P winter diets, respectively, and 4.2 and 3.6 g P/kg DM for the high and low P summer diets, respectively. A total of 95, 70, 50 and 22 cows completed each of lactations from 1 to 4, respectively. Neither the incidence of lameness or mastitis, or milk somatic cell count, were affected by dietary P level (P > 0.05), while none of the fertility parameters recorded in any of lactations from 1 to 4 was affected by the dietary P level (P > 0.05). Dietary P level had no effect on the specific gravity, ash or calcium content of rib cortical bone cores (n = 78 cows), while the P content of cortical bone (g/kg fresh, g/kg DM and mg/ml fresh bone) was lower with cows offered low P diets (P < 0.05). Dietary P level had no significant effect on the digestibility of either the DM, nitrogen, energy or acid detergent fibre fraction of the diet (P > 0.05), while faecal P excretions were reduced by a mean of 27 g/cow per day with cows offered the low P diets during the winter period. The results of this study indicate that dietary P levels can be reduced to proportionately 0.8 (approximately) of current UK feeding standards (Agricultural and Food Research Council, 1991), with no detrimental effect on dairy cow health or fertility, while having only minor effects on bone composition.     

Quality and safety evaluation of genetically engineered rice with soybean glycinin: analyses of the grain composition and digestibility of glycinin in transgenic rice

The composition of nutritionally and physiologically important molecules in transgenic rice with the soybean glycinin gene was determined and compared with that of a non-transgenic control. Except for the levels of protein, amino acids and moisture, no marked differences were found between the two kinds of rice. The protein content of the transgenic rice was about 20% higher than the control (control, 6.5 g/100 g; transgenic, 8.0 g/100 g) with a concomitantly lower moisture content. This increased protein content mainly resulted from the increased glycinin expressed in the transgenic rice, and the protein was susceptible to gastric and intestinal digestion juices. In parallel with the increased protein content, some important amino acids lacking in quantity in normal rice were replenished.     

Influence of dietary non-essential amino acid profile on growth performance and amino acid metabolism of Nile tilapia, Oreochromis niloticus (L.)

The quality of dietary protein is an important factor influencing the growth performance of fish. To evaluate the quality of protein, the variables commonly studied are the composition of the essential amino acids, the digestibility and the protein use efficiency. The goal of the present experiment was to test the effect of the dietary non-essential amino acid composition on the growth of Nile tilapia (Oreochromis niloticus). The fish were fed three purified diets differing only in their non-essential amino acid composition. The influence of the experimental diets on the growth performance, on the activity of enzymes involved in the amino acid metabolism, aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT), and on whole body delta(15)N values was investigated. Body mass, lipid, protein and energy gain differed significantly between the feeding groups. The activity of ASAT in the whole liver was significantly higher in fish with a positive protein balance compared to fish which lost protein. Whole body delta(15)N values of fish were negatively correlated with their body mass gain. Despite the poor utilisation of synthetic amino acids, the experiment indicates the importance of the dietary non-essential amino acid composition for the growth performance of fish. The study reveals the possibility to trace the utilisation of synthetic amino acids by determining the isotopic composition of dietary amino acids and tissues or whole bodies of animals.     

The disappearance of dry matter,nitrogen and amino acids in the gastrointestinal tract from Calliandra leaves

The total tract disappearance of dry matter (DM), nitrogen and amino acids in different Calliandra leaves harvested from Kenya and Zimbabwe were measured using the mobile bag technique. In the mobile bag measurements, disappearance was measured in the rumen in sacco, by pepsin–HCl hydrolysis in vitro and in the intestine. The hydrolysis in the pepsin–HCl solution was designed to mimic digestion in the abomasum. The total tract disappearance of DM, nitrogen, and amino acids were generally low. The highest total apparent DM, nitrogen and total amino acid disappearance obtained were 425 (g/kg), 458 (g/kg total nitrogen), and 593 (g/kg amino acid), respectively. There were differences between the leaves in the disappearance of DM, nitrogen and amino acids, and in the proportion of nutrients lost in the rumen, after pepsin–HCl hydrolysis and in the intestine. More DM, nitrogen, and amino acids in the leaves from Kenya disappeared in the intestine in comparison to the disappearance in leaves from Zimbabwe. The reasons for the differences between the nutritive values of the leaves is unclear but appears to be strongly influenced by the stage of growth and conditions in which the plants were grown.     

Fiber-bound nitrogen in gorilla diets: implications for estimating dietary protein intake of primates

Protein is essential for living organisms, but digestibility of crude protein is poorly understood and difficult to predict. Nitrogen is used to estimate protein content because nitrogen is a component of the amino acids that comprise protein, but a substantial portion of the nitrogen in plants may be bound to fiber in an indigestible form. To estimate the amount of crude protein that is unavailable in the diets of mountain gorillas (Gorilla beringei) in Bwindi Impenetrable National Park, Uganda, foods routinely eaten were analyzed to determine the amount of nitrogen bound to the acid-detergent fiber residue. The amount of fiber-bound nitrogen varied among plant parts: herbaceous leaves 14.5+/-8.9% (reported as a percentage of crude protein on a dry matter (DM) basis), tree leaves (16.1+/-6.7% DM), pith/herbaceous peel (26.2+/-8.9% DM), fruit (34.7+/-17.8% DM), bark (43.8+/-15.6% DM), and decaying wood (85.2+/-14.6% DM). When crude protein and available protein intake of adult gorillas was estimated over a year, 15.1% of the dietary crude protein was indigestible. These results indicate that the proportion of fiber-bound protein in primate diets should be considered when estimating protein intake, food selection, and food/habitat quality.     

Effects of lowering crude protein supply alone or in a combination with essential oils on productivity,rumen function and nutrient utilization in dairy cows

Lowering dietary protein concentration is known to decrease urinary nitrogen (N) losses and increase milk N efficiency in dairy cows, but it may negatively affect animal productivity. Plant-derived essential oils (EO) may alleviate these negative effects by improving the efficiency of rumen fermentation in cows fed reduced feed protein diets. The experiment was conducted to investigate the effects of lowering crude protein (CP) supply alone or in a combination with an EO product on feed intake, milk production and composition, rumen fermentation, total tract digestibility and N utilization in dairy cows. Twenty-one Holstein cows were used in a replicated 3 × 3 Latin square design experiment. Each period consisted of 14 days for adaptation and 14 days for data collection and sampling. Cows were randomly assigned to one of three experimental diets: a 165 g/kg CP diet (control), a 155 g/kg CP diet (LCP) and LCP supplemented with 35 g/day per cow EO (LCPEO). The dry matter (DM) intake was decreased by LCP and LCPEO compared with the control; there was no effect of EO on DM intake. Milk yield and composition and feed efficiency were similar among treatments. Ruminal pH, lactate, ammonia and volatile fatty acids concentrations were not affected by treatment, except increased valerate concentration by LCPEO compared with LCP. The supplementation of EO tended to decrease protozoal counts. The LCP and LCPEO increased total tract digestibility of DM and organic matter and decreased CP digestibility compared with the control. Supplementation with EO did not affect total tract digestibility of dietary nutrients compared with the control or LCP. The LCP and LCPEO decreased urinary and fecal N excretions and increased milk N efficiency; nitrogen losses were not affected by EO. In this study, lowering dietary CP by 10 g/kg decreased urinary and fecal N excretion without affecting productivity. The supplementation of EO to LCP had only minor effects on rumen fermentation and did not affect productivity, digestibility and N excretion in lactating dairy cows.     

Dietary protein source affects lipid metabolism in the European seabass (Dicentrarchus labrax)

The study was undertaken to evaluate the effects of dietary protein sources on lipogenesis and fat deposition in a marine teleost, the European seabass (Dicentrarchus labrax). Four isonitrogenous (crude protein (CP, Nx6.25), 44% DM) and isoenergetic (22-23 kJ/g DM) diets were formulated to contain one of the following as the major protein source: fish meal (FM), one of two soy protein concentrates (SPC) and corn gluten meal (CGM). Apparent digestibility coefficients of the diets and raw ingredients, as well as soluble nitrogen (ammonia and urea) and phosphorus excretion were measured. Growth rates of seabass fed plant protein-based diets were significantly lower than those fed fish meal based diet. The protein utilisation was strongly correlated to the dietary essential amino acids index. Measurements of N excretion (ammonia and urea nitrogen) confirmed these data. Daily fat gain at the whole body level ranged between 1.1 to 1.7 g/kg BW, with the highest values being recorded in fish fed the fish meal based diet. Levels of plasma triglycerides and cholesterol were lower in fish fed soy protein diets than in those fed the diet solely based on fish meal. Soy protein rich diets decreased the activities of selected hepatic lipogenic enzymes (glucose 6-phosphate dehydrogenase, malic enzyme, ATP-citrate lysase, acetylcoenzyme A carboxylase and fatty acid synthetase). Highest lipogenic enzyme activities where found in fish fed the fish meal diet, except for fatty acid synthetase which was increased in seabass fed the corn-gluten meal based diets. Overall data suggest that dietary protein sources affects fat deposition and the lipogenic potential in European seabass.     

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.     

Manipulation of amino acid composition in soybean seeds by the combination of deregulated tryptophan biosynthesis and storage protein deficiency

The ability of genetic manipulation to yield greatly increased concentrations of free amino acids (FAAs) in seeds of soybean was evaluated by introduction of a feedback-insensitive mutant enzyme of tryptophan (Trp) biosynthesis into two transformation-competent breeding lines deficient in major seed storage proteins. The storage protein-deficient lines exhibited increased accumulation of certain other seed proteins as well as of FAAs including arginine (Arg) and asparagine in mature seeds. Introduction of the gene for a feedback-insensitive mutant of an α subunit of rice anthranilate synthase (OASA1D) into the two high-FAA breeding lines by particle bombardment resulted in a >10-fold increase in the level of free Trp in mature seeds compared with that in nontransgenic seeds. The amount of free Trp in these transgenic seeds was similar to that in OASA1D transgenic seeds of the wild-type cultivar Jack. The composition of total amino acids in seeds of the high-FAA breeding lines remained largely unaffected by the expression of OASA1D with the exception of an increase in the total Trp content. Our results therefore indicate that the extra nitrogen resource originating from storage protein deficiency was used exclusively for the synthesis of inherent alternative nitrogen reservoirs such as free Arg and not for deregulated Trp biosynthesis conferred by OASA1D. The intrinsic null mutations responsible for storage protein deficiency and the OASA1D transgene affecting Trp content were thus successfully combined and showed additive effects on the amino acid composition of soybean seeds.     

Evaluation of optimum lysine and threonine supplements to a wheat and barley-based diet in rats

Experiments were conducted on growing male SPF-rats to study the optimum supplementation with essential amino acids of diets containing wheat and barley (1.4:1) as the only source of nitrogen. In growth and balance experiments comprising 30 and 17 combinations of L-lysine and L-threonine, respectively, the concentrations of the two amino acids corresponding to maximum body weight gain, feed conversion efficiency, biological value of protein and net protein utilization were calculated using multiple regression analysis. Addition of lysine and threonine to the basal diet markedly improved the nutritional value of cereal proteins. The optimum concentrations found were 0.69–0.70% total dietary lysine and 0.52–0.55% total dietary threonine. Statistical analysis showed that the number of observations used for the estimation of regression functions in the growth experiment could be reduced to ca. 100 without substantially affecting precision.     

Growth performance,carcass and noncarcass traits and meat quality of Barbarine lambs fed rosemary distillation residues

The aim of this experiment was to study the effect of total replacement of oat hay by rosemary distillation residues (RR) on growth, carcass characteristics and meat quality of Barbarine lambs. A total of 21 lambs were divided into three groups. The control group (C) was offered 600 g of oat hay; the RR87 and RR60 groups received 600 g of pellets containing 87% and 60% of RR, respectively. The CP content was 9% and 14% for RR87 and RR60, respectively. All animals were supplemented by 600 g of concentrate. After 77 days of fattening, lambs were slaughtered. The DM and CP intakes were significantly increased with RR diets. The average daily gain was higher (P<0.001), while the feed conversion rate was lower for RR60 and RR87 than C group. The dressing percentage was similar for all groups. The tissular (muscle, fat and bone) and the regional (leg, shoulder, etc.) carcass composition did not differ among groups. The bony organs and gut weights were similar among groups, while functional ones (skin, liver, kidney and testicles) were significantly heavier for both RR groups than control. The ultimate pH, water cooking loss and color variables were similar among groups and the chemical composition (protein, fat, myoglobin, collagen and iron) did not differ also among groups. These results revealed the opportunity of RR use in fattening lambs without adverse effects on carcass and meat characteristics. Moreover, 9% CP in RR pellets are enough given the same growth performance recorded as that of RR with 14% CP.     

Accumulation,assembly, and digestibility of amarantin expressed in transgenic tropical maize

An amaranth (Amaranthus hypochondriacus) 11S globulin cDNA, encoding one of the most important storage proteins (amarantin) of the seed, with a high content of essential amino acids, was used in the transformation of CIMMYT tropical maize genotype. Constructs contained the amarantin cDNA under the control of a tissue-specific promoter from rice glutelin-1 (osGT1) or a constitutive (CaMV 35S) promoter with and without the first maize alcohol dehydrogenase intron (AdH). Southern-blot analysis confirmed the integration of the amarantin cDNA, and copy number ranged from one to more than ten copies per maize genome. Western-blot and ultracentrifugation analyses of transgenic maize indicate that the expressed recombinant amarantin precursors were processed into the mature form, and accumulated stably in maize endosperm. Total protein and some essential amino acids of the best expressing maize augmented 32% and 8–44%, respectively, compared to non-transformed samples. The soluble expressed proteins were susceptible to digestion by simulated gastric and intestinal fluids, and it is suggested that they show no allergenic activity. These findings demonstrate the feasibility of using genetic engineering to improve the amino acid composition of grain crops.Communicated by J.W. Snape     

Dietary supplements of mixtures of indispensable amino acids lacking threonine, phenylalanine or histidine increase the activity of hepatic threonine dehydrogenase, phenylalanine hydroxylase or histidase, respectively, and prevent growth depressions in chicks caused by dietary excesses of threonine, phenylalanine, or histidine*

Experiments were carried out to determine whether the addition of a mixture of indispensable amino acids (IAA) lacking in threonine, phenylalanine or histidine, respectively, to a nutritionally complete diet would increase the hepatic activities of the rate-limiting enzymes for catabolism of threonine, phenylalanine or histidine and prevent the adverse effects of the amino acid on growth when the dietary level of the amino acid is excessive. Week old Leghorn chicks were fed semi-purified diets containing 19% crude protein to which were added no IAA supplement or 10% crude protein from an IAA mix and 5 graded levels of either L-threonine, L-phenylalanine or L-histidine in a 2 x 5 factorial arrangement of treatments. Each amino acid was investigated in a separate experiment involving four replicate pens (seven chicks each) per diet. Weight gains and feed consumptions were determined on the fourteenth day of each experiment. The groups receiving no excess, and 1.0% or 2.0% excesses of amino acids were sampled on the fifteenth day for enzyme activities and plasma amino acid concentrations. Weight gain and/or feed consumption were lower, and plasma concentrations of threonine, phenylalanine and histidine were higher, in chicks receiving 1.5 to 2.0% dietary additions of threonine, phenylalanine, and histidine, respectively, than in chicks that did not receive these amino acids. Chicks that received the amino acids in diets that also contained the IAA supplement had better growth and feed consumption, lower plasma concentrations of threonine, phenylalanine or histidine, higher plasma concentrations of other indispensable amino acids, and higher activities of threonine dehydrogenase, phenylalanine hydroxylase, and histidase than chicks receiving excess amino acids in the absence of IAA supplements. We conclude that the dietary level of protein, not the dietary level of individual amino acids, is the primary determinant of the activity of amino acid degrading enzymes in liver. The increased activity of these enzymes may be the mechanism by which dietary protein alleviates the adverse effects of excessive levels of individual amino acids.     

Minimum and optimum physiological doses of egg albumin and mutton protein in newly weaned rats

Using diets with a mounting egg albumin and mutton protein concentration, the authors determined the optimum physiological doses, which are identical with the maximum of linearity of the given parameters, from changes in body nitrogen, body weight and body water. The regression equations of the lines from these parameters were used to determine the minimum physiological doses for newly weaned rats. The optimum and minimum physiological doses of the amino acids in the relevant dietary proteins were also determined by analysing the source for its nitrogen content and other components and for the amino acid spectrum. The optimum dose of egg albumin protein for newly weaned rats was 1.69 g/day (on a 15% protein diet) and of mutton protein 2.56 g/day (on a 12.5% protein diet), with daily amounts of 60 mg methionine, 93 mg phenylalanine, 112 mg valine and 60 mg tyrosine for both proteins. The minimum doses of egg albumin and mutton protein, determined from changes in body nitrogen were 282 mg and 213 mg/day respectively [methionine 10.4 (4.7) mg/day, phenylalanine 16.1 (7.5) mg/day, valine 19.1 (9.2) mg/day and tyrosine 9.8 (5.2) mg/day)].     

Genetic analysis of dry matter and nitrogen accumulation and protein composition in wheat kernels

The maximum rate and duration for grain dry matter (DM) and nitrogen (N) accumulation were evaluated in 194 recombinant inbred lines (RILs) from a cross between the two French wheat cultivars Récital and Renan. These cultivars were previously identified as having contrasting kinetics of grain DM and N accumulation. Grain protein composition was analysed by capillary electrophoresis (CE), which enabled quantification of the different storage protein fractions (-gliadins, -gliadins, LMW glutenins, HMW glutenins, and each of their subunits). Correlation analyses revealed that DM and N accumulation rates were closely correlated and repeatable over several years, which was not the case for DM and N accumulation durations, and that protein composition was primarily influenced by the N accumulation rate. This was particularly true for the LMW-glutenins and the -gliadins, the most abundant protein fractions. A genetic map of 254 molecular markers covering nearly 80% of the wheat genome was used for quantitative trait loci (QTL) analysis. A total of seven QTLs were found. Five QTLs were significantly associated with the kinetics of DM and N accumulation, and two of them also influenced protein composition. Two QTLs affected only the protein composition. One major QTL explained more than 70% of the total variation in HMW-GS Glu1B-x content.