Rat Feeding Tests Research Articles

Regulatory Toxicology in Controversy

This article examines the way in which public controversies affect regulatory science. It describes the controversy that unfolded in Europe around the use of the ninety-day rat-feeding tests for the risk assessment of genetically modified (GM) plants. This type of test had been criticized for almost two decades by toxicologists, nongovernmental organizations, and industry alike for its inability to capture the specific health effects of GM plants. But GM risk assessment experts showed great reluctance to move toward a more systematic use of other tests, such as chronic two-year studies or toxicogenomic techniques, and made sure that official guidance continues to recommend the use of the ninety-day rat-feeding study. The article shows that these tactics of standardization are a defining feature of regulatory science, and a resource for toxicity experts to defend their authority and credibility against competing expertises that arise during controversies.

Biodegradation of Swine Waste by House-Fly Larvae and Evaluation of Their Protein Quality in Rats

Abstract Iniguez-Covarrubias, G., Franco-Gomez, Ma, de J. and Andrade- Maldonado, Gpe. del R. 1994. Biodegradation of swine waste by house fly larvae and evaluation of their protein quality in rats. J. Appl. Anim. Res., 6: 65–74. Swine waste was converted into a high-protein product by upgrading with housefly larvae. Fresh manure was seeded with housefly eggs. The eggs were allowed to hatch and the larvae to tunnel and aerate the manure. This process deodorized the manure by the 6th or 7th day. The larvae migrated out of the manure to a dry box. The larvae were dried, ground and used in rat feeding tests for the evaluation of the protein quality in terms of protein efficiency ratio (PER), the in vitro digestibility value of larvae meal protein was also determined. The larvae meal contained 52.5% C.P. of 90.6% digestibility with very high (29.1) percent of ether extract. It supported growth in rats as good as casein with PER 3.3 as against 3.1 for casein. If found economically viable on large scale, the pr...

Aspartyl- and Glutamyl-Lysine Crosslinks Formation and Their Nutritional Availability

Transglutaminase-catalyzed incorporation of L-lysine into wheat gliadin rendered the lysine-fortified protein poorly digestible in the in vitro tests. In rat feeding tests, however, the luminal leavings and excreta collected after administration of the [14C]lysine-fortified gliadin contained less than one-tenth of the radioactivity originally administered to rats. The enzymes, gamma-glutamylamine cyclotransferase and 5-oxoprolinase, known to occur in animal kidney are at least in part responsible for the observed high availability of isopeptide bound lysine. A novel enzyme which is capable of directly hydrolyzing the cross-linked isopeptide into component amino acids and peptides, "N epsilon-(gamma-glutamyl)lysine hydrolase" was found in the isolated microorganisms which can use the synthesized N epsilon-(gamma-glutamyl)lysine as their only source of carbon and nitrogen. The enzyme(s) appear to be effectively used for improving digestibility and availability of protein matrixes formed in normal metabolism and by heat and/or shear treatment commonly used in food processing.

Mycotoxins produced by toxic Fusarium isolates obtained from agricultural and nonagricultural areas (Arctic) of Norway

Twenty-five isolates of F. acuminatum, 38 of F. avenaceum, 1 of F. culmorum, 31 of F. oxysporum and 56 of F. sambucinum were obtained in 1983, 1984 and 1986 from cereal grains and soil from various parts of Norway. The isolates were grown on an autoclaved Uncle Ben's parboiled rice medium and examined for production of trichothecenes and other toxins and for toxicity in rat feeding tests. F. culmorum N46C(2) and Fusarium sambucimum 45-86-A produced zearalenone (F-2) 864 and 665 ppm, respectively and caused uterine enlargement in rats. Most of these isolates produced no known trichothecene mycotoxins that could account for the toxicity that was demonstrated in the rat feeding tests. All but F. avenaceum N26B produced fusarin C (1.5 ppm) but caused no toxic effects in rat feeding test. None of the isolates produced fusarochromanone (TDP-1). Thirteen isolates of F. acuminatum, 16 of F. avenaceum, 14 of F. oxysporum and 3 of F. sambucinum produced a cytotoxic factor which we named HM-8. One isolate of F. avenaceum, 12 of F. oxysporum and 46 of F. sambucinum produced a hemorrhagic factor which we named H-1 (wortmannin). Twenty isolates of F. acuminatum, 22 of F. avenaceum, 17 of F. oxysporum and 1 of F. sambucinum produced moniliformin. Four isolates of F. acuminatum, 9 of F. avenaceum, 25 of F. oxysporum and 52 of F. sambucinum caused death to rats. Three isolates of F. avenaceum, 19 of F. oxysporum and 47 of F. sambucinum induced hemorrhage in various organs. All isolates caused decreased weight gain, relative to the control diets.

Amine‐binding capacities of food proteins in transglutaminase reaction and digestibility of wheat gliadin with ϵ‐attached lysine

AbstractSeveral food proteins were examined for their capacity as substrate in transglutaminase reaction by using a fluorescent amine, monodansyl cadaverine, as donor substrate and following the increase in fluorescence of the reaction mixture. Wheat gluten, or one of its component proteins, gliadin, was the best acceptor among the proteins tested. Compared with intact protein, a preparation of wheat gliadin, modified by transglutaminase‐mediated incorporation of [14C]lysine, showed a marked decrease in in‐vitro digestibility. In rat feeding tests, however, the luminal leavings and excreta collected 24 h after administration of gliadin with ϵ‐attached [14C]lysine contained less than one‐tenth of the radioactivity originally administered. The results presented support the previous notion that occurrence of the ϵ‐γ isopeptide linkage in protein does not significantly impair the in‐vivo digestibility of the protein and nutritional availability of isopeptide bound lysine moieties.

Nutritional upgrading of a new soya‐protein isolate—SP55

AbstractA series of biochemical and nutritional studies was performed in order to establish the reasons for the poor nutritional quality of the new soya‐protein isolate SP55. Moist heat treatment which destroyed the substantial residual anti‐tryptic activity present in the SP55 fraction, did not improve the nutritive value of the protein as indicated by rat feeding tests. Furthermore, partial in‐vitro‐enzymic digestion by papain or by pancreatin of SP55 prior to rat feeding did not alter the poor performance of the preparation. Amino acid analysis indicated that the protein was deficient in several essential amino acids. Subsequent rat feeding studies showed that the nutritional quality of the protein can be highly upgraded by supplementation with sulphur‐containing amino acids, tryptophan and threonine.

The effect of aqueous leaching of glucosinolates on the nutritive quality of rapeseed meal.

AbstractStudies were conducted with the aim to upgrade the nutritional quality of high glucosinolate rapeseed meals, via heat treatment and aqueous leaching of the glucosinolates, under various conditions of temperature and pH. Conditions for thermal pretreatment of the seeds were sought which ensured complete inactivation of the enzyme myrosinase, no reduction in available lysine, and minimal losses of soluble protein during subsequent leaching processes. This was achieved by 30 min steaming at 100°C, although kinetic studies showed that complete inactivation of the enzyme took place within 5 min. Leaching experiments were performed with full‐fat flakes and with defatted meal. The rate as well as the total amount of leached glucosinolates was higher in defatted meal compared to full‐fat flakes. Protein losses were similar with both types of rapeseed raw material and were only slightly affected by changing the pH. Oil losses from full‐fat flakes during the leaching process were significant. Raising the leaching temperature from 25 to 50°C increased substantially the rate and the total amount of leached glucosinolates, but resulted in higher losses of protein. Generally, raising the pH of the leaching medium in the range of 4–8, resulted in an increase in the rate as well as in the total amount of leached glucosinolates. Rat feeding tests (PER) of leached meals indicated that raising the leaching temperature from 25 to 50°C lowered the protein quality of the meals. On the other hand, meals leached under the same temperature conditions, in the pH range of 4–8, were not found significantly different in their protein nutritive value. Substantial heat treatment was also found necessary for improving the nutritive quality of low glucosinolate rapeseed.

Evaluation of Linear Programming Techniques in Formulating Human Diets with Rat-feeding Tests

Diets in which the chief source of calories was either rice or wheat were formulated by linear programming to meet the requirements of the preschool child for energy, protein and amino acids. Chicken, fish, beef, eggs, whole milk, soy flour and amino acids were used to supplement the cereals to provide the necessary levels of protein and amino acids. Control diets based on egg protein and glucose were formulated to either satisfy or provide an excess above these requirements. The diets were compared in rat feeding tests. Rats fed diets based on wheat supplemented with intact protein or the amino acids lysine and methionine grew at a rate similar to those fed the control diets formulated to just meet the requirements. Rats fed diets based on rice supplemented with intact protein grew at a rate considerably faster than the control diet and also made comparatively faster growth than those fed the wheat diets. The studies indicate that linear programming can be used successfully to formulate human diets based on wheat. However, due to insufficient information on the nutritive value of rice and on the correlation between analytical and nutritive value of rice for humans, linear programming of diets based on rice was not completely successful as measured by uniformity of results. Requirements can be met by fortification of wheat with lysine and possibly methionine with no additional intact protein whereas fortification of rice with lysine alone is not satisfactory. J. Nutr. 103: 179-188, 1973.

Experiments with solvent extraction of glandless cottonseed and glanded cottonseed

AbstractPreliminary bench scale tests indicated that the rate of extraction of oil from glandless cottonseed flakes is about the same as for glanded flakes. Pilot plant experiments, using 20 lb. batches of flakes in baskets 8×8 in. in cross section, showed that the usual percolation rates can be used and will produce the same results with glandless flakes as with glanded. Solvents used were commercial hexane, nearly pure normal hexane, and a mixed solvent of acetone, hexane and water. In some runs raw flakes were extracted; in others, the meats were tempered by heating to various temperatures. Refine and bleach tests were run on the resulting oil. Colors were much lower than generally obtained with oil from glanded seed, most samples testing below one red Lovibond on a spectrophotometer. The meals from the extractions were used in rat feeding tests. The mixed solvent meal seemed to be a cut above the hexane‐extracted meals in protein quality, showing up equivalent to a casein based diet. The meal from meats which had been heated to 230 F seemed very slightly inferior to those which had undergone less drastic heating. All glandless meals were much superior to a commercial prepress solvent meal which was run for the purpose of making comparisons.

Elimination of aflatoxins from peanut meal.

AbstractPeanut meal containing aflatoxins was heat treated in the presence of moisture and chemicals to reduce the aflatoxin content. Treatments with ammonia, methylamine, sodium hydroxide and ozone were effective in either destroying aflatoxins or greatly reducing aflatoxin levels as indicated both by TLC analysis and feeding experiments with ducklings and rats. Weight gains for animals receiving the treated meals were essentially comparable to those for animals receiving aflatoxin‐free meal. The treated meals, however, had somewhat reduced protein efficiency ratios, as indicated by rat feeding tests. Complete elimination of aflatoxins from contaminated peanut meal was achieved by extraction with a 90% acetone‐10% water (w/w) solvent system. The extracted aflatoxin‐free peanut meal gave good growth in the duckling and rat feeding tests, and had a relatively high protein efficiency ratio.

Crambe seed processing: Filtration‐extraction on a bench scale

AbstractCrambe abyssinica is a potential source of erucic fatty acid and of good quality protein, provided satisfactory methods for processing the seed can be developed. Among the oil recovery methods currently under study is that of filtration‐extraction, a direct solvent process for high‐oil content seeds. Good oil recovery at satisfactory filtration rates was accomplished by a series of processing steps including dehulling, flaking, cooking, drying, crisping and extracting with hexane.When the conventional cook procedure was modified to incorporate an enzyme‐conversion step, significant improvement in rat feeding tests was obtained without loss in subsequent extraction efficiency. The recovered oils from the nonconversion cooks were refined and bleached by conventional procedures to oils of light color. The oil product from the conversion cook apparently contained sulfur compounds, even after refining and bleaching, whose removal will require special treatment as yet undeveloped in order to produce a hydrogenatable oil.

Physical Stability and Tinplate Deterioration in Cans of Evaporated Milk Held Under Refrigeration

Average changes after 4 yr in tin and iron content were not significant in comparison with the fresh control. However, there was a considerable can-to-can variation. The lead content was not significantly changed in storage. The visual color was not significantly darker, although reflectance at 400 mµ did indicate formation of browning compounds. The flavor (hedonic scale) was significantly changed in storage, when consumed as a beverage, but not in coffee. Milk fat separation, protein sedimentation, and lime grain (mineral deposit) were found not to be problems under these storage conditions. The pH dropped slightly (0.1 pH), whereas viscosity and whippability were normal and appeared unchanged relative to fresh controls. Vitamins B1 and B6 did not change, but B2 was reduced 25% and B12 reduced 33% of the original values. Rat feeding tests did not indicate a significant difference in protein quality between storage and control samples. There was some evidence of an increase in NPN and a substantial increase in free fatty acids during storage. Electrophoretic patterns were essentially the same for both the storage samples and controls.

The influence of temperature, heating time, and aeration upon the nutritive value of fats

AbstractIn order to determine the biological significance of the changes which occur when fats are heated to high temperatures in air, cottonseed oils were heated and aerated under several controlled conditions. In general, the data indicate that the changes induced are proportional to the severity of the conditions and that treatments more severe than those usually encountered in processing or cooking are necessary to produce detectable damage.Oils which had been subjected to prolonged aeration at 60C (16 days or more) or exposed to air in thin layers maintained at 180舑220C supplied less available energy and caused development of larger livers than untreated samples when compared in rat feeding tests. Heating in deep layers caused less damage than heating to the same temperatures in thin films, indicating that exposure to oxygen accelerates nutritional impairment.The cooking of food in fats changes condition so greatly that direct extrapolation of data obtained in tests using fat alone is not justified. Fat extracted from foods has not been found to contain harmful substances by the tests used.

Composition and Nutritive Value of Cheese Produced from Milk Treated with Hydrogen Peroxide and Catalase

Summary This study provides information on the nutritional value and wholesomeness of cheese made from milk treated with hydrogen peroxide at 5, 10, and 25 times the anticipated normal practical levels. The milks and their wheys obtained in preparing the cheese samples also were tested. The samples were analyzed for proximate composition and for the vitamins, niacin, thiamine, riboflavin, vitamin B 6 , pantothenic acid, folic acid, vitamin B 12 , vitamin A, and beta-carotene. The amino acids, methionine, cystine, tryptophane, and lysine, also were determined. Biological protein evaluation was done for milk, whey, and cheese by feeding these products to rats to provide 9% protein (dry-weight basis) as the sole source of protein in an otherwise complete ration. Additional rat-feeding tests were done on cheese which furnished 14% protein in the diet. The results indicated no marked changes in the composition or nutritive value of milk treated with 0.1, 0.2, and 0.5% hydrogen peroxide, or of the whey or cheese obtained from that milk.

Rat feeding tests with milk obtained from cows fed toxic cottonseed meal.

Rat feeding tests with milk obtained from cows fed toxic cottonseed meal.