Effect of animal protein supplementation and energy on the protein quality of diets based on rice and beans in adult males

Four short nitrogen balance index studies were carried out in adult subjects to evaluate the biological quality of a mixture based on rice and beans, and also to measure the effect of animal protein and/or energy supplementation on the nutritive value of the mixture. In the first study, rice supplied 60% and beans, 40% of the protein's diet, which was administered at an energy level of 45.5 kcal/kg/day of metabolizable energy. A regression coefficient of 0.76 +/- 0.11 was found between ingested nitrogen and nitrogen balance, and a value for nitrogen maintenance of 96.2 +/- 13.7 mg/kg/day. When this same diet was administered in the second study at a 51.2 kcal/kg/day of metabolizable energy, the regression coefficient was 0.80 +/- 0.13, and that of nitrogen for maintenance, 90.1 +/- 8.7 mg/kg/day, without differences being significant (P less than 0.05) for any of the two measures. In the third study, 10% of the mixture's protein was substituted by milk protein, and given at a level of 45.2 kcal/kg/day of metabolizable energy. In this case, the regression coefficient found was 0.96 +/- 0.08, and that of nitrogen for maintenance, 78.6 +/- 10.2 mg/kg/day. These values do differ significantly (P less than 0.05) from those found in the two previous studies. When the diet of the third study was administered to the same subjects at a level of 48.9 kcal/kg/day of metabolizable energy, the regression coefficient of the equation was 0.86 +/- 0.17, and that for maintenance nitrogen, 82.4 +/- 10.2 mg/kg/day. These values are statistically equal to those found in the third study and do differ significantly from those of the first two studies. Information indicates that the supplementary effect of protein and milk occurs mainly at the digestive level. It is therefore concluded that when rice and beans are consumed jointly, in the adequate proportions, they constitute an excellent-quality food for adult humans.     

Digestibility, protein value and protein requirements of diets based on plantain/bean and cassava/bean in young adults

Information is provided on the nitrogen intake for nitrogen equilibrium in young human adults fed a cassava/bean diet and a plantain/bean diet. Ten individuals participating in each study ingested levels of 0, 0.2, 0.4 and 0.6 g protein/kg/day at a constant energy level (45 kcal/kg/day), using the short-term nitrogen balance method with multiple intakes. Even with intakes of 105.7 and 117.4 mg N/kg/day for the cassava/bean and plantain/bean diets, the experimental subjects did not reach a positive balance. The protein digestibility of the diets was low, as had been confirmed previously for beans alone: 55.7% for the cassava/bean study and 50.4% for plantains/beans. The average quantity of nitrogen intake required to reach nitrogen equilibrium for the cassava/bean diet was 114.3 mg N/kg/day and for the plantain/bean diet, 111.9 mg N/kg/day. In the case of the cassava/bean diet, the variability was 81.3 to 172.4, and for plantain/beans, 83.6 to 219.3 mg/kg/day. In four of the five individuals who participated in both studies, the nitrogen intake required to reach nitrogen equilibrium was greater when fed the diet based on plantain/beans than when fed the cassava/beans diet. These data support the assertion that the protein requirement is not a simple figure. Individual variability is so great that, as has been suggested, it is necessary to add two standard deviations to the average figure to cover 97.5% of the population. The results of this investigation support the need to increase protein digestibility and protein quality of beans, since this is a food of major importance for large population segments in the developing countries.     

A new alternative for estimating recommendations of protein intake in humans. Protein requirements of an adult population fed with a diet based on rice and beans

This paper proposes a new approach to estimate the protein needs of a population; recommendations are also made on the protein intake of adults fed diets based on rice and beans. For this purpose, the nitrogen balance data previously reported for 40 adult human subjects who had participated in 160 nitrogen balance periods fed diets based on rice and beans, with and without animal protein and/or energy supplementation were used. The proposed method is based on the curvilinear response between nitrogen intake and its nitrogen balance. The second degree equation describing the relationship between nitrogen balance and intake is calculated. Using the mathematical concept of the first and second derivatives, the point of inflexion is obtained, and interpreted as that condition wherein the individual utilizes with maximum efficacy the ingested nitrogen; nitrogen ingestion, which corresponds to that point, is therefore taken as the dietary nitrogen recommendation for the individual. When the values obtained by means of the quadratic equation are compared to those obtained by the traditional linear equation, values were found to be statistically equal (p less than 0.05) for both calculation methods. The recommended protein intake of an adult population fed a diet based on rice and beans was 0.80 and 0.77 g/kg/day for the quadratic approach, and for the conventional method, respectively. When this diet was supplemented with 10% milk protein and with the same energy level, the calculated values were 0.64 and 0.71 g protein/kg/day for both methods, in this same order. The essential amino acid intake and absorption values were also calculated from the protein levels recommended by both methods to be in nitrogen balance, from a diet based on rice and beans. Findings revealed, in all cases, that the intakes of each and all essential amino acids met those levels indicated by FAO/WHO, with the exception of isoleucine and the sulphur-containing amino acids, which apparently limit the quality of the diet.     

Protein digestibility of methionine supplemented common beans (Phaseolus vulgaris) in adult human subjects

The study reports on the protein digestibility of five cultivars of common beans (Phaseolus vulgaris) of different color, tested in young adult human subjects, as the sole dietary protein source. Cheese protein was used as reference protein. The cooked beans provided 0.65 g protein/kg/day, and energy intake was adjusted to 45 kcal/kg/day. Results indicated apparent protein digestibility to vary from 49.6 to 62.1%. White colored beans showed the highest value, while black beans gave the lowest. Cheese protein showed an apparent protein digestibility of 76.2%. The true protein digestibility was calculated using the endogenous nitrogen excretion values obtained in the study, as well as literature values. Digestibility increased as expected, but it is still low as compared to other protein sources. A high correlation was found between dry matter digestibility and protein digestibility. Fecal nitrogen was fractionated between soluble and insoluble nitrogen in a 0.02 N NaOH solution. This assay was also carried out in the cooked beans, and findings revealed that the soluble nitrogen fraction was highly correlated with protein digestibility, with a correlation coefficient of -0.94. This fraction, still to be identified, could very well be responsible for the low digestibility values found for common beans in human subjects.     

Significance of soya trypsin inhibitors in nutrition

Although recent evidence clearly indicates that trypsin inhibitors (TI) and low protein digestibility are the major factors responsible for the pancreatic hypertrophic and growth inhibitory effects of raw soybeans, there was uncertainty regarding the biological threshold level of TI at which these biological effects occur. To obtain such data, dehulled defatted flakes (10% dietary protein) containing graded levels of TI were fed to weanling rats for 4 weeks in two feeding trials. Normal pancreas weights were obtained in rats fed samples in which only 54 to 68% of the original TI of raw soya flour was inactivated. In partially toasted flakes with a nitrogen digestibility value of 77%, the average tolerance level of dietary TI activity that did not cause pancreatic hypertrophy was calculated to be 385 mg TI/100 g diet. TI tolerance level at maximum nitrogen digestibility of 85%, which did not significantly lower weight gain and reduce protein efficiencey ratios, was 260 mg TI/100 g diet. Continuous ingestion of high levels of TI (459 mg TI/100 g diet) in a 20% protein diet for 215 days did not inhibit growth nor cause pancreatic hypertrophy when compared to rats fed toasted soya flour diets. Pancreatic hypertrophy that occurs in rats fed raw soya diets containing up to about 1300 mg TI/100 g diet for 35 days was reversed by switching the rats to control diets or to 30% toasted flour. In long-term feeding studies, no pancreatic hypertrophy occurred in rats fed commercial edible-grade soya flour, concentrate, or isolate from time of weaning to adulthood (ca. 300 to 330 days). TI content of the diets ranged from 178 to 310 mg/100 g diet. Microscopic examination of the pancreas revealed no abnormalities. Gross appearances of heart, kidney, spleen and liver were normal. In long-term feeding, vitamin B-12 supplements were needed to provide optimum growth and to maintain body weight. Results of numerous chemical analyses, relatively short-term human tests and long-term animal feeding studies indicate that with proper control of manufacturing processes, soya protein products can be produced that, in mixed diets, have protein nutritional value approaching that of animal protein.     

Chemical composition and evaluation of the protein quality of beans in adult humans by the short-term nitrogen balance method

Three varieties of common beans were chemically analyzed and their protein quality was evaluated in 12 human male adult subjects by the short-term nitrogen balance method. Chemical analyses were performed for both raw and cooked grains. Cooking reduced the trypsin inhibitors in 28 to 73%, hemagglutinins, 100%, tannins as acid tannic equivalents, 9 to 72%, and 55 to 75% as catequin equivalents, and alkali-soluble nitrogen in 65%. Red and black beans contained more residual trypsin inhibitors and tannins than white beans, while the latter contained more alkali-soluble nitrogen. Although cooked colored beans had more antinutritional factors that affect protein digestibility, their protein quality was similar to that of white beans. This could be explained by the fact that the amino acid composition and/or balance of red and black beans absorbed nitrogen is better than that of white beans, so that the final nutritional value will be determined by the sum of interactions between all factors. In this study, each of the three varieties presented at least one protein quality depressor in higher concentration than the other two varieties. Therefore, the overall differences found between treatments and residual effect, were small or non existent, while significant differences (p greater than 0.05) were found between subjects and nitrogen balance periods. A level of 0.65 g of bean protein/kg/day was not enough to maintain nitrogen balance in subjects fed a diet where beans were the only protein source. According to calculations, 0.9-1.0 g of bean protein/kg/day are necessary for nitrogen balance in male adults, and 1.2-1.3 g of protein bean would be the recommendation for a normal population.     

Rice and beans--effect of milk, mineral, and vitamin A, on weight gain, food intake, and body protein retention

Weanling rats were fed on diets of rice/beans (RB) with or without mineral (M) supplement; vitamin A (A); M + A (MA); or milk (L), containing from 3 to 14% protein. As determined by various measures, the best results were observed in the group fed the RB diet, supplemented with L. This group was followed by those receiving the MA and M diets. Protein utilization in the RB diet, as well as minimum protein requirement for maintaining body weight, depend on the supplementary nutrients. The mechanism of this effect may be related to the appetite of the animals and to the voluntary intake, which is influenced and regulated by the diet composition.     

prüfung von Leinfuttermitteln (Saat,Extraktionsschrot) an wachsenden Schweinen – Futterwert,Thiocyanat-und Schilddrüsenhormonstatus

Evaluation of linseed feedstuffs (ground linseed, solvent extracted linseed meal) with growing pigs – feed value, thiocyanate and thyroid hormone status. Ground linseed (Linum usitatissimum) was tested with 9 fattening pigs in a digestibility experiment. Barley (control diet) was partially replaced either by 25% or 50% ground linseed. In three periods three animals of each of the three groups (latin square) received a diet without or with 25% or 50% ground linseed. In two feeding experiments a total of 120 weaned piglets received diets either without and with 10% ground linseed or without and with 10% solvent extracted linseed meal (Exp. 2). A low apparent organic matter digestibility of 66% of ground linseed was primarily caused by 40% apparent digestibility of crude carbohydrates (crude fibre + N-free extract). In linseed groups the intake of lignin and its faecal excretion was high. It seems that the undigestible lignin is one, however not the sole reason of reduced digestibility. A relatively high metabolizable energy of 18MJ/kg linseed dry matter (DM) results from high fat content (40% of DM). Piglets receiving ground linseed tended to higher feed consumption as well as body weight gain and lower feed to gain ratio. As a tendency the consumption of diet with solvent extracted linseed meal and the daily weight gain were lower than in control (without linseed meal). Linseed feedstuffs drastically increased thiocyanate concentration of blood serum. Cyanide is released and detoxified via sulphur transferases to thiocyanate in organism.Thiocyanate impairs thyroid function, however, only in case of iodine deficiency. In case of 0.5 mg/kg diet supplementary iodine in piglet's experiments ground linseed had no effect on thyroxine and triiodothyronine concentration oi blood serum. A lower serum thyroxine concentration of piglets which were given the solvent extracted linseed meal resulted from other causes than from iodine administration (0.5 mg/kg diet).     

Digestibility and protein quality of quinua: comparative study of quinua (Chenopodium Quinoa) seed and flour in children

Based on the hypothesis that the digestibility of quinua seed is the limiting factor in the utilization of nutrients from this staple, two quinua-based diets were prepared using quinua seeds and quinua flour. Theses diets were offered to children recovering from malnutrition. The digestibility and protein quality of the quinua diets were compared to those of a casein control diet by analyzing the children's metabolic balance. Results showed that digestibility of the quinua diets were compared to those of a casein control diet by analyzing the children's metabolic balance. Results showed that digestibility of the quinua seed is the limiting factor in the protein and energy utilization, and that milling improves significantly the digestibility of fat and carbohydrates. Findings also confirmed that the protein quality of quinua seeds is adequate for human consumption.     

Evaluation of the nutritive value of soybean milk prepared with microwave-treated soybeans

Aqueous soybean extracts were prepared from beans, previously treated by microwaves to almost inactivate their lipoxygenase. These soy milks thus obtained were then nutritionally evaluated. All soy milks studied showed lower protein, fat, ash and total solids contents, as compared to a control milk prepared from soy beans not processed by microwaves. The milk obtained from soybeans with 8.7% initial moisture, treated by microwaves for 240 seconds, had the best total chemical score and the highest apparent methionine availability, as well as PER. The complete inactivation of the trypsin inhibitor activity was achieved with the milk prepared from soybeans with 56.8% initial moisture, subjected to microwave treatment for 180 seconds. On the other hand, the milk obtained from soybeans with 38.8% initial moisture, processed by microwaves for 180 seconds, resulted to have the highest, in vitro, protein digestibility.     

Proteins and amino acids: features and fulfillment of requirements with Latin American diets

Diets must supply enough nitrogen and essential amino acids to satisfy human needs. A diet's protein quality is associated to its digestibility, amino acid composition, protein concentration and dietary and preparation factors that enhance or reduce essential amino acid and protein bioavailability. Dietary energy intake also affects the utilization efficiency of dietary proteins. Protein quality of Latin American diets varies between countries and between socioeconomic groups in a given country. Most poor and lower-middle income persons consume diets with strong predominance of vegetable proteins. These diets are usually bulky, with relatively low protein concentration and energy density, and sometimes do not provide enough of one or more essential amino acids. In some countries and in some population groups, over 50% of the dietary proteins are of animal origin. This may be a risk factor of cardiovascular disease. Protein quality of Latin American diets, however, can be improved by modifying the proportions of some foods in order to achieve amino acid complementation, increase protein concentration and, in some instances, increase digestibility. Examples of diets that are satisfactory for preschool children and adults are given. Nevertheless, improvement of the overall nutritional quality of the diets is of foremost importance, so that they may provide the energy and all essential nutrients required for humans.     

Evaluation of the protein quality of meat flour from the tollo shark (Squalus acanthias)

The protein quality of tollo flour evaluated by various biological methods, including digestibility, is reported. The product contained 91.52% crude protein and 69.86% true protein, the difference being non-protein nitrogen, mainly urea. Due to this reason the biological evaluations were carried out with different shark flour concentrations and evaluated at different lengths of time with each method. Diets containing 0, 3, 6, 9 and 12% shark flour were prepared and evaluated by the PER, NPR, and NGI methods. Casein was used as reference protein. The protein digestibility was 91.2%, not corrected for non-protein nitrogen. On this same basis, PER and NPR--at a protein level of 9.97% in the diet--were 2.58 and 2.05, respectively. The casein control diet gave a PER of 2.93 and an NPR of 4.52. NGI was calculated by using the non-protein diet, or without it, with values of 3.32 and 2.95, respectively. As expected, all values corrected for non-protein nitrogen were higher for protein digestibility. The differences were significant at the 5% level. Apparently, urea influenced negatively the biological evaluations. It can be concluded, therefore, that the tollo shark meat is of excellent quality.     

Do Salivary Proline-Rich Proteins Counteract Dietary Hydrolyzable Tannin in Laboratory Rats?

We hypothesized that dietary hydrolyzable tannins would not act as digestibility reducing substances but would be excreted in the feces if the tannin were ingested by rats producing salivary proline-rich proteins (PRPs). To test that hypothesis we used two groups of Sprague–Dawley rats: tannin-naïve rats that were secreting basal levels of salivary PRPs and tannin-habituated rats that were secreting elevated levels of PRPs. The animals were fed for 10–18 d on diets containing 3% (w/w) purified hydrolyzable tannin [pentagalloyl glucose (PGG)] that was periodically spiked with chemically synthesized, radiolabeled 1,2,3,4,6-penta-O-galloyl-[U-¹⁴ C]-d-glucopyranose (1 μCi per gram diet). The PGG-habituated rats excreted three times more of the consumed ¹⁴ C in their feces than did the PGG-naïve rats (11.4% for PGG-habituated rats vs. 3.5% for PGG-naïve rats, P < 0.05). The addition of 3% PGG to the diet of the PGG-naïve rats had no significant effect on apparent dry matter or nitrogen digestibility (P > 0.05). However, dry matter digestibility and nitrogen digestibility were significantly decreased by PGG in the diets of the PGG-habituated rats (7 and 25%, P < 0.001, respectively). Production of PRPs increased the amount of PGG excreted intact in the feces but at the cost of diminishing apparent dry matter and nitrogen digestibility.     

FORAGING IN CHEMICALLY DIVERSE ENVIRONMENTS: ENERGY,PROTEIN, AND ALTERNATIVE FOODS INFLUENCE INGESTION OF PLANT SECONDARY METABOLITES BY LAMBS

Interactions among nutrients and plant secondary metabolites (PSM) may influence how herbivores mix their diets and use food resources. We determined intake of a food containing a mix of terpenoids identified in sagebrush (Artemisia tridentata) when present in isoenergetic diets of increasing concentrations of protein (6, 9, 15, or 21% CP) or in isonitrogenous diets of increasing concentrations of energy (2.17, 2.55, 3.30, or 3.53 Mcal/kg). Lambs were offered choices between those diets with or without terpenes or between diets with terpenes and alfalfa hay. Intake of the diets with terpenes was lowest with the lowest concentrations of protein (6%) and energy (2.17 Mcal/kg) in the diets, and highest with diets of 15% CP and 3.53~Mcal/kg. In contrast, when terpenes were absent from the diets, lambs consumed similar amounts of all four diets with different concentrations of protein, and more of the diets with intermediate amounts of energy. When given a choice between the diet with or without terpenes, lambs preferred the diet without terpenes. When lambs were offered choices between terpene-containing diets and alfalfa, energy and protein concentrations influenced the amount of terpenes animals ingested. Energy densities higher than alfalfa, and protein concentrations higher than 6%, increased intake of the terpene-containing diet. Thus, the nutritional environment interacted with terpenes to influence preference such that lambs offered diets of higher energy or protein concentration ate more terpenes when forced, but not when offered alternative food without terpenes. The nutrients supplied by a plant and its neighbors likely influence how much PSM an animal can ingest, which in turn may affect the dynamics of plant communities, and the distribution of herbivores in a landscape. We discuss implications of these findings for traditional views of grazing refuges and varied diets in herbivores.     

Rice protein extracted by different methods affects cholesterol metabolism in rats due to its lower digestibility

To elucidate whether the digestibility is responsible for the hypocholesterolemic action of rice protein, the effects of rice proteins extracted by alkali (RP-A) and α-amylase (RP-E) on cholesterol metabolism were investigated in 7-week-old male Wistar rats fed cholesterol-free diets for 3 weeks. The in vitro and in vivo digestibility was significantly reduced by RP-A and RP-E as compared to casein (CAS). The digestibility was lower in RP-E than that of RP-A. Compared with CAS, the significant cholesterol-lowering effects were observed in rats fed by RP-A and RP-E. Fecal excretion of bile acids was significantly stimulated by RP-E, but not by RP-A. The apparent cholesterol absorption was more effectively inhibited by RP-E than RP-A because more fecal neutral sterols were excreted in rats fed RP-E. There was a significant correlation between protein digestibility and cholesterol absorption (r = 0.8662, P < 0.01), resulting in a significant correlation between protein digestibility and plasma cholesterol level (r = 0.7357, P < 0.01) in this study. The present study demonstrates that the digestibility of rice protein affected by extraction method plays a major role in the modulation of cholesterol metabolism. Results suggest that the hypocholesterolemic action induced by rice protein with lower digestibility primarily contribute to the inhibition of cholesterol absorption.     

Use of chigo (Campsiandra comosa Benth) seeds in human nutrition. III. Energetic value of chiga flour

The proximate composition as well as vitamin and mineral contents of a sample of chiga (Campsiandra comosa Benth) flour was analyzed, having determined that it was essentially a carbohydrate source. The product was evaluated as source of energy, substituting 33, 67 and 100% of the corn starch of isoproteic and isocaloric feeds for growing Sprague-Dawley rats. In an experimental period of 15 days, results indicated that the substitution of one-third of the carbohydrate with chiga flour did not reduce the weight gain, food consumption, metabolizable energy or utilization of the food energy by the rats. Higher levels of the product in the diet originated a decrement in these variable values. The apparent nitrogen and energy digestibility of the diets was progressively reduced as the concentration range of chiga flour utilized was increased. The metabolizable energy value of chiga flour was 3.15 kcal/g, which indicated that approximately 78% of its gross energy (4.01 kcal/g) was metabolized.     

Separate effects of dietary protein and fat on serum cholesterol levels: another view of amino acid content of proteins

Casein or soy protein with vegetable or animal fat were used to determine the dietary protein or fat effects and their possible interaction on serum cholesterol levels. Young, male New Zealand white rabbits with a mean weight of 2.1 kg were divided into groups of six and fed one of four different diets containing 20% of the calories as protein, 30% as fat (according to dietary guidelines for the United States) and 50% as carbohydrate. The diets contained casein or soy (lysine/arginine ratio = 2.2 or 0.9, respectively) as the protein sources with fat from either almond oil or butter. There was no significant difference in weight gain among the diet groups. Total serum cholesterol level was highest among animals fed the diet containing butter with casein (177 +/- 25 mg/dl) or soy protein (189 +/- 50 mg/dl), it was intermediate in animals fed the vegetable oil with casein (121 +/- 14 mg/dl), and lowest in the soy protein with vegetable oil group (58 +/- 12 mg/dl). There was a significant difference in serum cholesterol levels due to the protein effect when vegetable oil was used (p less than 0.05) but not with butter. There was also a significant fat effect on serum cholesterol when the diet contained soy protein (p less than 0.005) but not when the protein was casein. No significant interaction was observed between the dietary fat and protein sources on serum cholesterol levels, which suggests that dietary protein and fat independently affect the levels of serum cholesterol. Thus, dietary protein has a significant effect on serum cholesterol levels and may be a factor in the low levels of serum cholesterol observed among vegetarians and in humans of Third World countries where the diets is primarily of vegetable origin.     

Use of earthworms as a protein supplement in diets for rabbits

The purpose of the present study was to evaluate the nutritive value of earthworms as protein feed in rabbit rations. Earthworm meal was obtained from Eisenia foetida and Lumbricus rubellus. Its proximate chemical composition, amino acid composition and protein digestibility in vitro were determined. In addition, growing rabbits were fed a diet containing 30% of the total protein as earthworm meal, diet which was compared with a control diet containing soybean meal as protein feed. Both diets were isocaloric and isonitrogenous. Feed intake, weight gain, feed conversion and apparent digestibility were measured. Results showed high protein (50.86%) and fat (10.16%) contents, and low fiber percentage (2.67%). Amino acids content including the essential, and in vitro protein digestibility percentage were similar to fish and meat meals and higher than soybean meal. There were no differences in feed intake, weight gain and feed conversion. Apparent digestibility was 5.09% higher (P less than 0.05) with the diet containing earthworm meal than with the control diet. It was concluded that it is possible to substitute 30% of the protein in the diet of growing rabbits, with earthworm meal, without any adverse physiological effects. Similar results to those achieved when conventional protein supplements are used for rabbit rations, were obtained.     

Effect of dietary vitamin E levels on fatty acid profiles and nonenzymatic lipid peroxidation in the guinea pig liver

Guinea pigs were fed for five weeks with three diets containing different levels of vitamin E: LOW (but nondeficient, 15 mg of vitamin E/kg diet), MEDIUM (150 mg/kg diet), and HIGH (1,500 mg/kg diet). Dietary vitamin E supplementation did not change oxidative stress indicators in the hydrophilic compartment but increased liver α-tocopherol in a dose-dependent way and strongly decreased sensitivity to nonenzymaticin vitro liver lipid peroxidation. This last effect was already observed in group MEDIUM, and no further decrease inin vitro lipid peroxidation occurred from group MEDIUM to group HIGH. The protective effect of vitamin E againstin vitro lipid peroxidation was observed even though an optimum dietary concentration of vitamin C for this animal model was present in the three different vitamin E diets. Both HIGH and LOW vitamin E decreased percentage fatty acid unsaturation in all phospholipid fractions from membrane origin in relation to group MEDIUM. The results, together with previous information, show that both vitamin E and vitamin C at intermediate concentrations are needed for optimal protection against lipid peroxidation and loss of fatty acid unsaturation even in normal nonstressful conditions. These protective concentrations are higher than those needed to avoid deficiency syndromes.     

Effect of Linseed Fed as Rolled Seeds,Extruded Seeds or Oil on Fatty Acid Rumen Metabolism and Intestinal Digestibility in Cows

Linseed, a source of linolenic acid, is used in ruminant diets to increase polyunsaturated fatty acids (FA) in animal products. Seed processing is known to have an impact on FA rumen metabolism, but few data are available for linseed. We studied the effect of linseed lipid on ruminal metabolism and intestinal digestibility in cows. Three modes of linseed processing: rolled linseed (RL), extruded linseed (EL) and linseed oil plus linseed meal (LO), supplemented at 7.5% of DM intake, were compared to a control diet (C). Duodenal flows, intestinal digestibility and plasma composition were determined. The duodenal flow of linolenic acid was similar among diets. The sum of t10 and t11-18:1, which were coeluted, was increased with lipid-supplemented diets and represented more than 60% of trans 18:1 for EL and LO diets. The main 18:2 isomers were c9, c12 and t11, c15 among the non-conjugated isomers, and t11, t13 among CLA. Linseed supplementation increased the duodenal flow of unsaturated intermediates of biohydrogenation, and this effect was more pronounced for extruded seeds and oil than for rolled seeds. For most 18-carbon FA, intestinal digestibility was slightly higher for C and LO diets than for RL and EL. Plasma concentrations of non-conjugated 18:2 and linolenic acid were similar among the lipid-supplemented diets. Within diet, profiles of 18:1 isomers (except c9) remained very similar between duodenal and plasma FA.